Under the core-accretion model, gas giants form via runaway accretion. This process starts when the mass of the accreted envelope becomes equal to the mass of the core. We modeled a population of warm sub-Saturns to search for imprints of their formation history in their internal structure. Using the GAS gianT modeL for Interiors (GASTLI), we calculated a grid of interior structure models on which we performed retrievals for our sample of 28 sub-Saturns to derive their envelope mass fractions (f_env). For each planet, we ran three different retrievals, assuming low (−2.0<log (Fe/H)<0.5), medium (0.5<log (Fe/H)<1.4), and high (1.4<log (Fe/H)<1.7) atmospheric metallicity. The distribution of f_env in our sample was then compared to outcomes and predictions of planet formation models. When our results are compared to the outcomes of a planetesimal accretion formation model, we find that we require a high atmospheric metallicity for intermediate-mass sub-Saturns to reproduce the simulated planet population. For higher planetary masses, a medium atmospheric metallicity provides the best agreement. Additionally, we find a bimodal distribution of f_env in our sample with a gap that is located at different values of f_env for different atmospheric metallicities. For the high atmospheric metallicity case, the gap in the f_env distribution is located between 0.5 and 0.7, which is consistent with assumptions of the core-accretion model in which runaway accretion starts when M_env ≍ M_core(f_env is ∼ 0.5). We also find a bimodal distribution of the hydrogen and helium mass fraction (f_H/He) with a gap at f_H/He=0.3. The location of this gap is independent of the assumed atmospheric metallicity. Lastly, we compared the distributions of our sub-Saturns in the Neptunian savanna to a population of sub-Saturns in the Neptune desert and ridge. We find that the observed f_env distribution of savanna and ridge sub-Saturns is consistent with the planets coming from the same underlying population.

Triboson production processes play a crucial role in probing the electroweak sector of the Standard Model, as they involve quartic gauge-boson couplings already at the tree level. With these measurements entering the precision era at the Large Hadron Collider (LHC), accurate theoretical predictions become indispensable. We present the computation of the next-to-next-to-leading-order (NNLO) QCD radiative corrections to the production of a $W$ boson in association with two photons ($Wγγ$) at the LHC. The calculation is exact, except for the finite part of the two-loop contribution, which is included in the leading-colour approximation. Predictions for the fiducial cross section and selected kinematic distributions are provided at a centre-of-mass energy of $\sqrt{s}=13$ TeV, under standard experimental selection cuts. In line with observations for other multiboson processes involving direct photons, we find sizable NNLO corrections that enhance the next-to-leading-order predictions by about $23\%$, with residual perturbative uncertainties that can be roughly estimated to be at the $5\%$ level.

Autochemotaxis, the directed movement of cells along gradients in chemicals they secrete, is central to the formation of complex spatiotemporal patterns in biological systems. Since the introduction of the Keller-Segel model, numerous variants have been analyzed, revealing phenomena such as coarsening of aggregates, stable aggregate sizes, and spatiotemporally chaotic dynamics. Here we consider general mass-conserving Keller-Segel models, that is, models without cell growth and death, and analyze the generic long-time dynamics of the chemotactic aggregates. Building on and extending our previous work, which demonstrated that chemotactic aggregation can be understood through a generalized Maxwell construction balancing density fluxes and reactive turnover, we use singular perturbation theory to derive the rates of mass competition between well-separated aggregates. We analyze how this mass-competition process drives coarsening in both diffusion- and reaction-limited regimes, with the diffusion-limited rate aligning with our previous quasi-steady-state analyses. Our results generalize earlier mathematical findings, demonstrating that coarsening is driven by self-amplifying mass transport and aggregate coalescence. Additionally, we provide a linear stability analysis of the lateral instability, predicting it through a nullcline-slope criterion that parallels the curvature criterion in spinodal decomposition. Overall, our findings suggest that chemotactic aggregates behave similarly to phase-separating droplets, providing a robust framework for understanding the coarse-grained dynamics of autochemotactic cell populations and a quantitative basis for comparing chemotactic coarsening to canonical nonequilibrium phase separation.

Biological and artificial systems encode information through complex nonlinear operations across multiple timescales. A clear understanding of the interplay between this multiscale structure and the nature of nonlinearities at play is, however, missing. Here, we study a general model where the input signal is propagated to an output unit through a processing layer via nonlinear activation functions. We focus on two widely implemented paradigms: nonlinear summation, where signals are first nonlinearly transformed and then combined; nonlinear integration, where they are combined first and then transformed. We find that fast-processing capabilities systematically enhance input-output mutual information, and nonlinear integration outperforms summation in large systems. Conversely, a nontrivial interplay between the two strategies emerges in lower dimensions as a function of interaction strength, heterogeneity, and sparsity of conections between the units. Finally, we reveal a tradeoff between input and processing sizes in strong-coupling regimes. Our results shed light on relevant features of nonlinear information processing with implications for both biological and artificial systems.

In 2023, Belle II collaboration announced the observarion of the $B^+ \to K^+ ν\barν$ decay channel for the first time. This decay channel provides a clean signal with high precision in theoretical calculation. However, we encounter $2.8σ$ deviation from the Standard Model (SM) prediction. To resolve this excess, we study scalar dark matter (DM) model with local discrete $Z_3$ symmetry. Assuming dark $U(1)_X \equiv U(1)_{L_μ- L_τ}$ symmetry, this $U(1)_{L_μ- L_τ}$ symmetry is spontaneously broken into local discrete $Z_3$ by non-zero vacuum expectation value of dark Higgs boson. Considering dark Higgs mass is $2$GeV, we can explain the recent ${\rm Br} (B^+ \to K^+ ν\barν)$ excess reported from Belle II collaboration and relic abundance at the same time.

The measurement of the bound-state <inline-formula> <tex-math>$ \beta $</tex-math> </inline-formula> decay of ²⁰⁵Tl at the Experimental Storage Ring (ESR) at GSI, Darmstadt, has recently been reported, with substantial impact on the use of ²⁰⁵Pb as an early Solar System chronometer and on the low-energy measurement of the solar neutrino spectrum via the LOREX project. Owing to the technical challenges in producing a high-purity ²⁰⁵Tl⁸¹⁺ secondary beam, a robust statistical method was developed to estimate the variation in the contaminant ²⁰⁵Pb⁸¹⁺ produced in the fragmentation reaction, which was subsequently transmitted and stored in the ESR. Here, we show that Bayesian and Monte Carlo methods produce comparable estimates for the contaminant variation, each with unique advantages and challenges given the complex statistical problems for this experiment. We recommend the adoption of such methods in future experiments that exhibit unknown statistical fluctuations. *This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 682841 "ASTRUm" and No. 654002 "ENSAR2"). The research of G. Leckenby, I. Dillmann, and C. Griffin was funded by the Canadian Natural Sciences and Engineering Research Council (NSERC) via the grant SAPIN-2019-00030. J. Glorius, M. S. Sanjari, Yu. A. Litvinov and C. Brandau acknowledge support by the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006). E. Menz and Yu. A. Litvinov acknowledge support by the project "NRW-FAIR", a part of the programme "Netzwerke 2021", an initiative of the Ministry of Culture and Science of the State of North Rhine-Westphalia. R. Gernhäuser acknowledges support by the Excellence Cluster ORIGINS from the German Research Foundation DFG (Excellence Strategy EXC-2094─390783311)

We present primordial non-Gaussianity predictions from a new high-precision code for simulating axion-U(1) inflation on a discrete lattice. We measure the primordial scalar curvature power spectrum and bispectrum from our simulations, determining their dependence on both scale and axion-gauge coupling strength. Both the gauge-sourced power spectrum and the bispectrum exhibit a strong blue tilt due to our choice of an <inline-formula><mml:math><mml:mi>α</mml:mi></mml:math></inline-formula>-attractor inflaton potential. We provide fitting functions for the power spectrum and bispectrum that accurately reproduce these statistics across a wide range of scales and coupling strengths. While our fitting function for the bispectrum has a separable form, results from high-resolution simulations demonstrate that the full shape is not separable. Thus, our simulations generate realizations of primordial curvature perturbations with nontrivial correlators that cannot be generated using standard techniques for primordial non-Gaussianity. We derive bounds on the axion-gauge coupling strength based on the bispectrum constraints from the cosmic microwave background, demonstrating a new method for constraining inflationary primordial non-Gaussianity by simulating the nonlinear dynamics.

Context. Multiple photometric studies have reported the presence of seemingly older accreting pre-main-sequence (PMS) stars in optical colour-magnitude diagrams (CMDs). These sources appear bluer than the majority of cluster members, leading to older isochronal age estimates. Aims. We investigated this phenomenon in the Orion Nebula, which harbours a subset of stars that show infrared excess detected by Spitzer (which indicates the presence of protoplanetary discs) and Hα excess emission (which traces ongoing mass accretion), yet seem to have significantly older isochronal ages (≳10 Myr) than the bulk population (∼1−3 Myr) in the r, (r − i) CMD. This raises the question of whether these stars are truly older or whether their photometric properties are affected by observational biases or other physical processes. Methods. We performed a detailed spectroscopic analysis of 40 Orion Nebula stars using VLT/X-Shooter, covering CMD-based isochronal ages from 1 to over 30 Myr. We derived extinction values, stellar properties, and accretion parameters by modelling the ultraviolet excess emission via a multi-component fitting procedure. The sample spans spectral types from M4.5 up to K6, and masses in the range ∼0.1−0.8 M_⊙. Results. We demonstrate that when extinction and, more importantly, accretion effects are accurately constrained, the stellar luminosity and effective temperature of the majority of the seemingly old stars become consistent with a younger population (∼1−5 Myr). This is supported by strong lithium absorption (EW_Li ≳ 400 mÅ), which corroborates their youth, and by the accretion-to-stellar luminosity ratios (L_acc/L_⋆) typical for young, accreting stars. Three of these sources, however, remain old even after our analysis, despite showing signatures consistent with ongoing accretion from a protoplanetary disc. More generally, our analysis indicates that excess continuum emission from accretion shocks affects the placement of PMS stars in the CMD, displacing sources towards bluer optical colours. Conclusions. This study highlights the critical role of accretion in shaping stellar property estimates (including age) derived from optical CMDs and emphasises the need to carefully account for accretion effects when interpreting age distributions in star-forming regions. Understanding these biases is essential for accurately constraining the early evolution of PMS stars. ⋆ Based on observations collected at the European Southern Observatory under ESO programmes 0108.C-0919 and 0114.D-0441.

Neutron supermirrors are a crucial part of many scattering and particle physics experiments. So far, Ni(Mo)/Ti supermirrors have been used in experiments that require to transport a polarized neutron beam due to their lower saturation magnetization compared to Ni/Ti supermirrors. However, next generation <mml:math><mml:mi>β</mml:mi></mml:math> decay experiments require supermirrors that depolarize below <mml:math><mml:mrow><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> per reflection to reach their targeted precision. The depolarization of a polarized neutron beam due to reflection off Ni(Mo)/Ti supermirrors has not yet been measured to that precision. Recently, Cu/Ti supermirrors with a lower saturation magnetization compared to Ni(Mo)/Ti have been developed, and may serve as an alternative. In this paper, we test the performance of both mirrors. At a first stage, we present four-states polarized neutron reflectivity curves of Ni(Mo) and Cu monolayers and <mml:math><mml:mrow><mml:mi>m</mml:mi><mml:mo>=</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:math> Ni(Mo)/Ti and Cu/Ti supermirrors measured at the neutron reflectometer SuperADAM and perform a full polarization analysis, with the aim to extract information about their magnetic moment. The results found, however, were inconclusive, since it seems a detection limit of this method for all measured samples was reached. At a second stage, we measured the depolarization (<mml:math><mml:mi>D</mml:mi></mml:math>) that a polarized neutron beam suffers after reflection off the same Ni(Mo)/Ti and Cu/Ti supermirrors by using the Opaque Test Bench setup. We find upper limits for the depolarization of <mml:math><mml:mrow><mml:msub><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mtext>Cu/Ti(4N5)</mml:mtext></mml:mrow></mml:msub><mml:mo>&lt;</mml:mo><mml:mn>7</mml:mn><mml:mo>.</mml:mo><mml:mn>6</mml:mn><mml:mo>×</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>, <mml:math><mml:mrow><mml:msub><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mtext>Ni(Mo)/Ti</mml:mtext></mml:mrow></mml:msub><mml:mo>&lt;</mml:mo><mml:mn>8</mml:mn><mml:mo>.</mml:mo><mml:mn>5</mml:mn><mml:mo>×</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>, and <mml:math><mml:mrow><mml:msub><mml:mrow><mml:mi>D</mml:mi></mml:mrow><mml:mrow><mml:mtext>Cu/Ti(2N6)</mml:mtext></mml:mrow></mml:msub><mml:mo>&lt;</mml:mo><mml:mn>6</mml:mn><mml:mo>.</mml:mo><mml:mn>0</mml:mn><mml:mo>×</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> at the <mml:math><mml:mrow><mml:mn>1</mml:mn><mml:mi>σ</mml:mi></mml:mrow></mml:math> confidence level, where (4N5) corresponds to a Ti purity of <mml:math><mml:mrow><mml:mn>99</mml:mn><mml:mo>.</mml:mo><mml:mn>995</mml:mn><mml:mspace></mml:mspace><mml:mstyle><mml:mi>%</mml:mi></mml:mstyle></mml:mrow></mml:math> and (2N6) to <mml:math><mml:mrow><mml:mn>99</mml:mn><mml:mo>.</mml:mo><mml:mn>6</mml:mn><mml:mspace></mml:mspace><mml:mstyle><mml:mi>%</mml:mi></mml:mstyle></mml:mrow></mml:math>. These results show that all three supermirrors are suitable for being used in next generation <mml:math><mml:mi>β</mml:mi></mml:math> decay experiments. We found no noticeable dependence of the depolarization on the <mml:math><mml:mi>q</mml:mi></mml:math> value or the magnetizing field, in which the samples were placed.

Forward modeling the galaxy density within the Effective Field Theory of Large Scale Structure (EFT of LSS) enables field-level analyses that are robust to theoretical uncertainties. At the same time, they can maximize the constraining power from galaxy clustering on the scales amenable to perturbation theory. In order to apply the method to galaxy surveys, the forward model must account for the full observational complexity of the data. In this context, a major challenge is the inclusion of redshift space distortions (RSDs) from the peculiar motion of galaxies. Here, we present improvements in the efficiency and accuracy of the RSD modeling in the perturbative LEFTfield forward model. We perform a detailed quantification of the perturbative and numerical error for the prediction of momentum, velocity and the redshift-space matter density. Further, we test the recovery of cosmological parameters at the field level, namely the growth rate f, from simulated halos in redshift space. For a rigorous test and to scan through a wide range of analysis choices, we fix the linear (initial) density field to the known ground truth but marginalize over all unknown bias coefficients and noise amplitudes. With a third-order model for gravity and bias, our results yield < 1 % statistical and < 1.5 % systematic error. The computational cost of the redshift-space forward model is only ∼ 1.5 times of the rest frame equivalent, enabling future field-level inference that simultaneously targets cosmological parameters and the initial matter distribution.

Systematic effects can hinder the sought-after detection of primordial gravitational waves, impacting the reconstruction of the B-mode polarization signal which they generate in the cosmic microwave background (CMB). In this work, we study the impact of an imperfect knowledge of the instrument bandpasses on the estimate of the tensor-to-scalar ratio r in the context of the next-generation LiteBIRD satellite. We develop a pipeline to integrate over the bandpass transmission in both the time-ordered data (TOD) and the map-making processing steps. We introduce the systematic effect by having a mismatch between the "real", high resolution bandpass τ, entering the TOD, and the estimated one τ_s , used in the map-making. We focus on two aspects: the effect of degrading the τ_s resolution, and the addition of a Gaussian error σ to τ_s . To reduce the computational load of the analysis, the two effects are explored separately, for three representative LiteBIRD channels (40 GHz, 140 GHz and 402 GHz) and for three bandpass shapes. Computing the amount of bias on r, ∆r, caused by these effects on a single channel, we find that a resolution ≲ 1.5 GHz and σ ≲ 0.0089 do not exceed the LiteBIRD budget allocation per systematic effect, ∆r < 6.5 × 10^-6. We then check that propagating separately the uncertainties due to a resolution of 1 GHz and a measurement error with σ = 0.0089 in all LiteBIRD frequency channels, for the most pessimistic bandpass shape of the three considered, still produces a ∆r < 6.5 × 10^-6. This is done both with the simple deprojection approach and with a blind component separation technique, the Needlet Internal Linear Combination (NILC). Due to the effectiveness of NILC in cleaning the systematic residuals, we have tested that the requirement on σ can be relaxed to σ ≲ 0.05.

We present imaging and spectroscopic observations of supernova SN 2025wny, associated with the lens candidate PS1 J0716+3821. Photometric monitoring from the Lulin and Maidanak observatories confirms multiple point-like images, consistent with SN 2025wny being strongly lensed by two foreground galaxies. Optical spectroscopy of the brightest image with the Nordic Optical Telescope and the University of Hawaii 88-inch Telescope allows us to determine the redshift to be z_s = 2.008 +- 0.001, based on narrow absorption lines originating in the interstellar medium of the supernova host galaxy. At this redshift, the spectra of SN 2025wny are consistent with those of superluminous supernovae of Type I. We find a high ejecta temperature and depressed spectral lines compared to other similar objects. We also measure, for the first time, the redshift of the fainter of the two lens galaxies (the "perturber") to be z_p = 0.375 +- 0.001, fully consistent with the DESI spectroscopic redshift of the main deflector at z_d = 0.3754. SN 2025wny thus represents the first confirmed galaxy-scale strongly lensed supernova with time delays likely in the range of days to weeks, as judged from the image separations. This makes SN 2025wny suitable for cosmography, offering a promising new system for independent measurements of the Hubble constant. Following a tradition in the field of strongly-lensed SNe, we give SN 2025wny the nickname SN Winny.

One of the most promising approaches for future neutrinoless double beta decay searches is to incorporate a candidate isotope into the liquid scintillator of a next-generation neutrino detector. In this study, a sample of the high-performance 1,2,4-Trimethylbenzene-based liquid scintillator from the Borexino detector was loaded with different concentrations of Te-diols. Therefore,a novel and completely water-free synthesis in a non-acidic organic environment at room temperature was used. Key parameters of the loaded samples were analyzed and compared with those of the pure Borexino liquid. Both the emission spectrum and transmission remained nearly unchanged,even at high doping levels. The reduction in light yield was moderate, with approximately 8,400 photons emitted for a 1 MeV energy deposition by an electron at 1$\%$ tellurium loading. The time profile of the light emission induced by alpha particles was also investigated, revealing that the scintillation response becomes significantly faster with increasing tellurium concentration.

To give more credence to the M-theoretic Emergence Proposal it is important to show that also classical kinetic terms in a low energy effective action arise as a quantum effect from integrating out light towers of states. We show that for compactifications of type IIA on Calabi-Yau manifolds, the classical weak coupling Yukawa couplings, which are the triple intersection numbers of the Calabi-Yau threefold, can be obtained from the 1/2-BPS protected one-loop Schwinger integral over D2-D0 bound states, after employing a novel regularization for the final infinite sum of Gopakumar-Vafa invariants. Approaching the problem in a consecutive manner from 6D decompactification over emergent string to the ultimate M-theory limits, we arrive at a mathematically concrete regularization that involves finite distance degeneration limits of Calabi-Yau threefolds in an intriguing way. We test and challenge this proposal by the concrete determination of the periods around such degeneration points for threefolds with one Kähler modulus and the two examples ℙ_{1, 1, 1, 6, 9}[18] and ℙ_{1, 1, 2, 2, 6}[12].

We perform a lattice calculation of the correlators of two chromoelectric fields in the adjoint representation connected by adjoint Wilson lines at nonzero temperature. These correlators arise in the study of quarkonium dynamics and of adjoint heavy quark diffusion in deconfined matter. We work in SU(3) gauge theory using either gradient flow or multilevel algorithms for noise reduction, and discuss the renormalization of the correlators on the lattice. We find that a Casimir factor rescaling relates the adjoint correlators corresponding to the diffusion of an adjoint heavy quark and the octet-octet quarkonium transitions to the chromoelectric correlator in the fundamental representation describing the diffusion of a heavy quark.

Effective field theory (EFT) modeling is expected to be a useful tool in the era of future higher-redshift galaxy surveys such as DESI-II and Spec-S5 due to its robust description of various large-scale structure tracers. However, large values of EFT bias parameters of higher-redshift galaxies could jeopardize the convergence of the perturbative expansion. In this paper we measure the bias parameters and other EFT coefficients from samples of two types of star-forming galaxies in the state-of-the-art MilleniumTNG and astrid hydrodynamical simulations. Our measurements are based on the field-level EFT forward model that allows for precision EFT parameter measurements by virtue of cosmic variance cancellation. Specifically, we consider approximately representative samples of Lyman-break galaxies (LBGs) and Lyman-<inline-formula><mml:math><mml:mi>α</mml:mi></mml:math></inline-formula> emitters (LAEs) that are consistent with the observed (angular) clustering and number density of these galaxies at <inline-formula><mml:math><mml:mi>z</mml:mi><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:math></inline-formula>. Reproducing the linear biases and number densities observed from existing LAE and LBG data, we find quadratic bias parameters that are roughly consistent with those predicted from the halo model coupled with a simple halo occupation distribution model. We also find nonperturbative velocity contributions (fingers of God) of a similar size for LBGs to the familiar case of luminous red galaxies. However, these contributions are quite small for LAEs despite their large satellite fraction values of up to <inline-formula><mml:math><mml:mo>∼</mml:mo><mml:mn>30</mml:mn><mml:mo>%</mml:mo></mml:math></inline-formula>. Our results indicate that the effective momentum reach <inline-formula><mml:math><mml:msub><mml:mi>k</mml:mi><mml:mi>max</mml:mi></mml:msub></mml:math></inline-formula> at <inline-formula><mml:math><mml:mi>z</mml:mi><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:math></inline-formula> for LAEs (LBGs) will be in the range <inline-formula><mml:math><mml:mrow><mml:mn>0.3</mml:mn><mml:mo>−</mml:mo><mml:mn>0.6</mml:mn><mml:mi>h</mml:mi><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mi>Mpc</mml:mi><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> (<inline-formula><mml:math><mml:mrow><mml:mn>0.2</mml:mn><mml:mo>−</mml:mo><mml:mn>0.8</mml:mn><mml:mi>h</mml:mi><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mi>Mpc</mml:mi><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>), suggesting that EFT will perform well for high-redshift galaxy clustering. This work provides the first step toward obtaining realistic simulation-based priors on EFT parameters for LAEs and LBGs.

We derive an explicit BRST-exact operator identity for the bulk Hamiltonian in quantum gravity, working within a BRST-invariant quantization of General Relativity, treated as a low-energy effective field theory. We show that, up to a boundary term, the Hamiltonian can be written elegantly as the anticommutator of the BRST charge and the temporal ghost field. This form makes manifest that the Hamiltonian flow acts as a time-reparameterization on the correlation functions of the physical degrees of freedom. We demonstrate that the BRST-exactness of the bulk Hamiltonian does not trivialize the time evolution of gravitational backgrounds or bulk correlators, nor does it trivialize scattering amplitudes.

Context. The kinematics of the Milky Way bulge is known to be complex, reflecting the presence of multiple stellar components with distinct chemical and spatial properties. In particular, the bulge hosts a bar structure exhibiting cylindrical rotation, and a central velocity dispersion peak extending vertically along the Galactic latitude. However, due to severe extinction and crowding, observational constraints near the Galactic plane are sparse, underscoring the need for additional data to improve the completeness and accuracy of existing kinematic maps, and enabling robust comparison with dynamical models. Aims. This work aimed to refine the existing analytical models of the Galactic bulge kinematics by improving constraints in the innermost regions. We present updated maps of the mean velocity and velocity dispersion by incorporating new data near the Galactic plane. Methods. We combined radial velocity measurements from the GIBS and APOGEE surveys with both previously published and newly acquired MUSE observations. A custom-developed Python-based tool, PHOTfun, was used to extract spectra from MUSE datacubes using PSF photometry based on DAOPHOT-II, with an integrated GUI for usability. The method included a dedicated extension, PHOTcube, optimized for IFU datacubes. We applied Markov Chain Monte Carlo techniques to identify and correct for foreground contamination and to derive new analytical fits for the velocity and velocity dispersion distributions. Our analysis included nine new MUSE fields located close to the Galactic plane, bringing the total number of mapped fields to 57 including 23 000 individual RV measured. Results. The updated kinematic maps confirm the cylindrical rotation of the bulge and reveal a more boxy morphology in the velocity dispersion distribution, while preserving a well-defined central peak. The PHOTfun software, designed for flexible PSF photometry and spectral extraction from IFU data, is publicly available via pip for the community.

We present $\texttt{SBi3PCF}$, a simulation-based inference (SBI) framework for analysing a higher-order weak lensing statistic, the integrated 3-point correlation function (i3PCF). Our approach forward-models the cosmic shear field using the $\texttt{CosmoGridV1}$ suite of N-body simulations, including a comprehensive set of systematic effects such as intrinsic alignment, baryonic feedback, photometric redshift uncertainty, shear calibration bias, and shape noise. Using this, we have produced a set of DES Y3-like synthetic measurements for 2-point shear correlation functions $ξ_{\pm}$ (2PCFs) and i3PCFs $ζ_{\pm}$ across 6 cosmological and 11 systematic parameters. Having validated these measurements against theoretical predictions and thoroughly examined for potential systematic biases, we have found that the impact of source galaxy clustering and reduced shear on the i3PCF is negligible for Stage-III surveys. Furthermore, we have tested the Gaussianity assumption for the likelihood of our data vector and found that while the sampling distribution of the 2PCF can be well approximated by a Gaussian function, the likelihood of the combined 2PCF + i3PCF data vector including filter sizes of $90'$ and larger can deviate from this assumption. Our SBI pipeline employs masked autoregressive flows to perform neural likelihood estimation and is validated to give statistically accurate posterior estimates. On mock data, we find that including the i3PCF yields a substantial $63.8\%$ median improvement in the figure of merit for $Ω_m - σ_8 - w_0$. These findings are consistent with previous works on the i3PCF and demonstrate that our SBI framework can achieve the accuracy and realism needed to analyse the i3PCF in wide-area weak lensing surveys.

Context. The Fornax cluster is one of the closest X-ray-bright galaxy clusters; as such, we can study the system at high spatial resolution. However, previous observations of the intracluster medium were limited to less than R₅₀₀. Aims. We aim to significantly extend the X-ray coverage of the Fornax cluster and to search for features in the X-ray surface brightness distribution beyond R₅₀₀ induced by the gravitational growth of this system. Methods. We used data from five SRG/eROSITA all-sky surveys and performed a detailed one- and two-dimensional X-ray surface brightness analysis, tracing hot gas emission from kiloparsec to megaparsec scales with a single instrument. We compared the results to those from a recent numerical simulation of the local Universe (SLOW) and correlated the X-ray emission distribution with that of other tracers, including cluster member galaxies, ultra-compact dwarf galaxies, intracluster globular clusters, and HI-tail galaxies. Results. We detect X-ray emission out to well beyond the virial radius, R₁₀₀ = 2.2 deg. In the inner regions within R₅₀₀, we see previously known features, such as a large-scale spiral-shaped edge; however, we do not find obvious evidence of the bow shock several hundred kiloparsecs south of the cluster center predicted by previous numerical simulations of the Fornax cluster. Instead, we discover emission fingers beyond R₅₀₀ to the west and southeast and excesses that stretch out far beyond the virial radius. They might be due to gas being pushed outward by the previous merger with NGC 1404 or due to warm-hot gas infall along large-scale filaments. Intriguingly, we find the distributions of the other tracers ─ galaxies and globular clusters ─ to be correlated with the X-ray-excess regions, favoring the infall scenario. Interestingly, we also discover an apparent bridge of low-surface-brightness emission beyond the virial radius connecting to the Fornax A galaxy group, which is also traced by the member galaxy and globular cluster distribution. This X-ray bridge furthermore approximately coincides with a region of enhanced Faraday depth detected previously. The gas distribution in the SLOW simulation shows similar features as those we have discovered with SRG/eROSITA. Conclusions. SRG/eROSITA has enabled us to tremendously expand the view of the intracluster medium of the Fornax cluster. We witness the growth of a cluster along large-scale filaments.

We use the narrow [Ne v] λ3427 emission line detected in the recently published JWST spectra of two galaxies, at z ≃ 6.9 and 5.6, to study the key properties of the active galactic nuclei (AGN) and the supermassive black holes (SMBHs) in their centers. Using a new empirical scaling linking the <inline-formula> <mml:math><mml:mfenced><mml:mrow><mml:mi>Ne</mml:mi><mml:mspace></mml:mspace><mml:mi>V</mml:mi></mml:mrow></mml:mfenced></mml:math> </inline-formula> line emission with AGN accretion-driven (continuum) emission, derived from a highly complete low-redshift AGN sample, we show that the <inline-formula> <mml:math><mml:mfenced><mml:mrow><mml:mi>Ne</mml:mi><mml:mspace></mml:mspace><mml:mi>V</mml:mi></mml:mrow></mml:mfenced></mml:math> </inline-formula> emission in the two z > 5 galaxies implies total (bolometric) AGN luminosities of order L_bol ≍ (4─8) × 10⁴⁵ erg s⁻¹. Assuming that the radiation emitted from these systems is Eddington limited, the (minimal) black hole (BH) masses are of order M_BH ≳ 10⁷ M_⊙. Combined with the published stellar masses of the galaxies, estimated from dedicated fitting of their spectral energy distributions, the implied BH-to-stellar mass ratios are of order M_BH/M_host ≍ 0.1─1. This is considerably higher than what is found in the local Universe, but is consistent with the general trend seen in some other z ≳ 5 AGN. Given the intrinsic weakness of the <inline-formula> <mml:math><mml:mfenced><mml:mrow><mml:mi>Ne</mml:mi><mml:mspace></mml:mspace><mml:mi>V</mml:mi></mml:mrow></mml:mfenced></mml:math> </inline-formula> line and the nature of the <inline-formula> <mml:math><mml:mfenced><mml:mrow><mml:mi>Ne</mml:mi><mml:mspace></mml:mspace><mml:mi>V</mml:mi></mml:mrow></mml:mfenced></mml:math> </inline-formula>─to─L_bol scaling, any (rare) detection of the [Ne v] λ3427 line at z > 5 would translate to similarly high AGN luminosities and SMBH masses, thus providing a unique observational path for studying luminous AGN well into the epoch of reionization, including obscured sources.

Feedback from active galactic nuclei (AGNs) is crucial for regulating galaxy evolution. Motivated by observations of broad absorption line winds from rapidly accreting supermassive black holes (SMBHs), we introduce the MISTRAL AGN feedback model, implemented in the AREPO code. MISTRAL comes in two versions: continuous radial (MISTRAL-CONTINUOUS) and stochastic bipolar momentum deposition (MISTRAL-STOCHASTIC). Using the framework of the IllustrisTNG simulations, we explore the effect of MISTRAL on BH and galaxy properties, through an idealized Milky Way-mass galaxy and cosmological zoom simulations run down to <inline-formula><tex-math>$z=2$</tex-math></inline-formula>. Unlike standard thermal AGN feedback prescriptions, MISTRAL generates galaxy-scale winds that mimic outflows driven by BH accretion. MISTRAL-CONTINUOUS produces short-lived galactic fountains, and is inefficient at regulating the growth of massive galaxies at <inline-formula><tex-math>$z=2$</tex-math></inline-formula>. In contrast, MISTRAL-STOCHASTIC efficiently suppresses star formation in massive galaxies, reproduces the empirical stellar-to-halo mass relation, and yields a consistent trend of BH-stellar mass evolution. By supporting large-scale outflows while simultaneously preventing gas inflows, MISTRAL-STOCHASTIC additionally regulates the cold and hot gas fractions at both galaxy and halo scales. MISTRAL-STOCHASTIC therefore works self-consistently across the halo mass range explored <inline-formula><tex-math>$\left(10^{12}\!-\!3\times 10^{13}\, \rm M_\odot \right)$</tex-math></inline-formula>, without adopting an SMBH-mass-dependent AGN feedback scheme such as the one used in IllustrisTNG. Our model is a promising tool for predicting the impact of AGN winds on galaxy evolution, and interpreting the growing population of high-redshift galaxies and quasars observed by James Webb Space Telescope. This work is part of the 'Learning the Universe' collaboration, which aims to infer the physical processes governing the evolution of the Universe.

The strongly lensed supernova (SN) Encore, at a redshift of z = 1.949 and discovered behind the galaxy cluster MACS J0138−2155 at z = 0.336, provides a rare opportunity for time-delay cosmography and studies of the SN host galaxy, where previously another SN, called SN Requiem, had appeared. To enable these studies, we combined new James Webb Space Telescope (JWST) imaging, archival Hubble Space Telescope (HST) imaging, and new Very Large Telescope (VLT) spectroscopic data to construct state-of-the-art lens mass models that are composed of cluster dark-matter (DM) haloes and galaxies. We fitted the surface brightness distributions of the galaxies in the field of view using Sérsic profiles to determine their photometric and structural parameters across six JWST and five HST filters. We used the colour-magnitude and colour-colour relations of spectroscopically confirmed cluster members to select additional cluster members, and identified a total of 84 galaxies belonging to the galaxy cluster. We constructed seven different mass models using a variety of DM halo mass profiles and explored both multi-plane and approximate single-plane lens models. As constraints, we used the observed positions of 23 multiple images from eight multiple image systems that originate from four galaxies with distinct spectroscopic redshifts in the range of 0.767─3.420. In addition, we used stellar velocity dispersion measurements to obtain priors on the galaxy mass distributions. We find that six of the seven models fit well to the observed image positions, with a root-mean-square (rms) scatter of ≤0.032″ between the model-predicted and observed positions for systems identified with JWST and HST images, including SN Encore and SN Requiem (the rms scatter is 0.24″ for all positions, including those identified with MUSE images). Mass models with cored-isothermal DM profiles fit well to the observations, whereas the mass model with a Navarro-Frenk-White cluster DM profile has an image-position χ² value that is four times higher. We built our ultimate model by combining four multi-lens-plane mass models in order to incorporate uncertainties due to model parameterizations. Our two approximate mass models with a single-lens plane allow us to perform direct comparisons with single-plane models built independently by other teams. Using our ultimate model, we predict the image positions and magnifications of SN Encore and SN Requiem. We also provide the effective convergence and shear of SN Encore for micro-lensing studies. Our work lays the foundation for building state-of-the-art mass models of the cluster for future cosmological analysis and SN host galaxy studies.

This study explores the impact of observational and modelling systematic effects on cluster number counts and cluster clustering and provides model prescriptions for their joint analysis, in the context of the \Euclid survey. Using 1000 \Euclid-like cluster catalogues, we investigate the effect of systematic uncertainties on cluster summary statistics and their auto- and cross-covariance, and perform a likelihood analysis to evaluate their impact on cosmological constraints, with a focus on the matter density parameter $Ω_{\rm m}$ and on the power spectrum amplitude $σ_8$. Combining cluster clustering with number counts significantly improves cosmological constraints, with the figure of merit increasing by over 300\% compared to number counts alone. We confirm that the two probes are uncorrelated, and the cosmological constraints derived from their combination are almost insensitive to the cosmology dependence of the covariance. We find that photometric redshift uncertainties broaden cosmological posteriors by 20--30\%, while secondary effects like redshift-space distortions (RSDs) have a smaller impact on the posteriors -- 5\% for clustering alone, 10\% when combining probes -- but can significantly bias the constraints if neglected. We show that clustering data below $60\,h^{-1}\,$Mpc provides additional constraining power, while scales larger than acoustic oscillation scale add almost no information on $Ω_{\rm m}$ and $σ_8$ parameters. RSDs and photo-$z$ uncertainties also influence the number count covariance, with a significant impact, of about 15--20\%, on the parameter constraints.

In cosmological simulations of large-scale structure, star formation and feedback in galaxies are modelled by so-called subgrid models, which represent a physically motivated approximation of processes occurring below the resolution limit. However, when additional physical processes are considered in these simulations, for instance, magnetic fields or cosmic rays, they are often not consistently coupled within the descriptions of the underlying subgrid star formation models. Here, we present a careful study on how one of the most commonly used subgrid models for star formation in current large-scale cosmological simulations can be modified to self-consistently include the effects of non-thermal components (e.g. magnetic fields) within the fluid. We demonstrate that our new modelling approach, which includes the magnetic pressure as an additional regulation on star formation, can reproduce global properties of the magnetic field within galaxies in a set-up of an isolated Milky Way-like galaxy simulation, but is also successful in reproducing local properties such as the anticorrelation between the local magnetic field strength with the local star formation rate as observed in galaxies (i.e. NGC 1097). This reveals how crucial a consistent treatment of different physical processes is within cosmological simulations and gives guidance for future simulations.

Over the past LIGO--Virgo--KAGRA (LVK) observing runs, it has become increasingly clear that identifying the next electromagnetic counterparts to gravitational-wave (GW) neutron star mergers will likely be more challenging compared to the case of GW170817. The rarity of these GW events, and their electromagnetic counterparts, motivates rapid searches of any candidate binary neutron star (BNS) merger detected by the LVK. We present our extensive photometric and spectroscopic campaign of the candidate counterpart AT2025ulz to the low-significance GW event S250818k, which had a ${\sim} 29\%$ probability of being a BNS merger. We demonstrate that during the first five days, the luminosity and color evolution of AT2025ulz are consistent with both kilonova and shock cooling models, although a Bayesian model comparison shows preference for the shock cooling model, underscoring the ambiguity inherent to early data obtained over only a few days. Continued monitoring beyond this window reveals a rise and color evolution incompatible with kilonova models and instead consistent with a supernova. This event emphasizes the difficulty in identifying the electromagnetic counterparts to BNS mergers and the significant allotment of observing time necessary to robustly differentiate kilonovae from impostors.

Deep learning (DL) has been shown to outperform traditional, human-defined summary statistics of the Lyα forest in constraining key astrophysical and cosmological parameters owing to its ability to tap into the realm of non-Gaussian information. An understanding of the impact of nuisance effects such as noise on such field-level frameworks, however, still remains elusive. In this work we conduct a systematic investigation into the efficacy of DL inference from noisy Lyα forest spectra. Building upon our previous, proof-of-concept framework (Nayak et al. 2024) for pure spectra, we constructed and trained a ResNet neural network using labeled mock data from hydrodynamical simulations with a range of noise levels to optimally compress noisy spectra into a novel summary statistic that is exclusively sensitive to the power-law temperature-density relation of the intergalactic medium. We fit a Gaussian mixture surrogate with 23 components through our labels and summaries to estimate the joint data-parameter distribution for likelihood free inference, in addition to performing inference with a Gaussian likelihood. The posterior contours in the two cases agree well with each other. We compared the precision and accuracy of our posterior constraints with a combination of two human defined summaries (the 1D power spectrum and PDF of the Lyα transmission) that have been corrected for noise, over a wide range of continuum-to-noise ratios (CNR) in the likelihood case. We found a gain in precision in terms of posterior contour area with our pipeline over the said combination of 65% (at a CNR of 20 per 6 km/s) to 112% (at 200 per 6 km/s). While the improvement in posterior precision is not as large as in the noiseless case, these results indicate that DL still remains a powerful tool for inference even with noisy, real-world datasets.

Context. Large-scale agglomerations of galaxy clusters are the most massive structures in the Universe. To what degree they are actually bound against an accelerating expansion of the background cosmology is of significant cosmological as well as astrophysical interest. In this study, we introduce a crossmatched set of superclusters from the SLOW constrained simulations of the local (z < 0.05) Universe. These simulations combine a central region constrained by local velocity field data and realistic baryonic physics models within a 500 Mpc/h Box to reproduce the locally observed large-scale structure in detail. Aims. Identifying the local superclusters provides estimates on the efficacy of the constraints in reproducing the local large-scale structure accurately. The simulated counterparts can help to identify possible future observational targets containing interesting features, such as bridges between pre-merging and merging galaxy clusters and collapsing filaments, and provide comparisons for current observations. By numerically determining the collapse volumes for the simulated counterparts, we further elucidate the dynamics of cluster-cluster interactions in those regions. Methods. Starting from observational catalogs of local superclusters and the most massive clusters from the SLOW simulations already identified in previous works, we searched for simulated counterparts of supercluster members of six regions. We evaluated the significance of these detections by comparing the observed geometries to supercluster regions in random simulations. We then ran an N-body version of the SLOW initial conditions into the far future and determined which of the member clusters are gravitationally bound to the host superclusters. Furthermore we computed masses and density contrasts for the collapse regions. Results. We demonstrate that the SLOW constrained simulation of the local Universe accurately reproduces local supercluster regions not only in terms of the mass of their members but also in the individual clusters' 3D geometrical arrangement relative to each other. We furthermore find the bound regions of the local superclusters to be consistent in both size and density contrast with previous theoretical studies. This will allow us to connect future numerical zoom-in studies of the clusters to the large-scale environments and specifically the supercluster environments these local galaxy clusters evolve in. The zoom-ins will focus on ICM properties, turbulence, and nonthermal emission and build on the existing work concerned with the environments of local galaxy clusters.

Submoons, moons orbiting other moons, may be exotic environments capable of hosting extraterrestrial life. We extend previous studies to revise the maximum lifetime of these objects due to planetary, lunar and sublunar tidal migration. Using the Euler-Lagrange equation with a tidal dissipation process as specified by the Constant Geometric Lag model, we derive and solve the governing equations numerically to map the semi-major axis parameter space for star-planet-moon-submoon systems in which the submoon could be massive enough to host life. We find that Earth could have hosted asteroid-sized submoons ($\sim10^{15}\mathrm{kg}$), whereas a submoon near the previously proposed upper limit ($\sim4.6\cdot10^{17}\mathrm{kg}$) would have driven the Moon $\sim30\%$ farther from Earth than its current orbit. A Warm Jupiter system like Kepler1625 has greater potential of hosting a massive submoon. We found that a submoon of around $10\%M_{\text{Luna}}$ could survive if Kepler1625b's hypothesized moon were $68\%$ farther away then what the best-fit model suggests ($67R_{\mathrm{p}}$ instead of $40R_{\mathrm{p}}$). Giant submoons of mass $1.8M_{\oplus}$ are stable in a Kepler1625-like system. In these cases, the moon orbit is wide ($> 100R_{\mathrm{p}}$). Decreasing the submoon mass to a habitability prerequisite of $0.5M_{\oplus}$, likely needed for a stable atmosphere and plate tectonics, leads to a smaller total number of stable iterations relative to the $m_{sm}=1.8M_{\oplus}$ case. In fact, we identified a minimum number of stable iterations on intermediate submoon mass-scales of around $0.1M_{\oplus}$. This is likely due to an interplay between small tidal forces at small submoon masses and small Roche-Limits at very high submoon masses. If submoon formation pathways in Warm Jupiter systems prefer such intermediate mass-scales, habitable submoons could be a rare phenomenon.

Radio observations provide a window into a planet's interior and play a crucial role in studying its atmosphere and surface, key factors to find potential habitability. The discovery of thousands of exoplanets, together with advances in radio astronomy through the Square Kilometre Array (SKA), motivates the search for planetary-scale radio emissions. Here, we employ the radiometric Bode's law (RBL) and machine learning techniques to analyze a dataset of 1330 confirmed exoplanets, aiming to estimate their potential radio emission. Permutation Importance (PI) and SHapley Additive exPlanations (SHAP) analyses indicate that a planet's mass, radius, orbital semi-major axis, and distance from Earth are sufficient to dependably forecast its radio flux and frequency. The random forest model accurately reproduces these radio characteristics, confirming its reliability for exoplanetary radio predictions. Considering observational constraints, we find that 64 exoplanets could generate signals detectable by the SKA, 52 of which remain observable in the intermediate AA* deployment. Among these, MASCARA-1 b stands out with a predicted flux of 7.209 mJy at 135.1 MHz, making it an excellent SKA-Low target. Meanwhile, WASP-18 b, with a flux of 18.638 mJy peaking at 812.9 MHz, is the most promising candidate for SKA-Mid. These results show that the SKA can detect gas giants, such as MASCARA-1 b (SNR>400) and WASP-18 b (SNR>4236), within feasible integration times. Additionally, we identify four candidates (HATS-18 b, WASP-12 b, WASP-103 b, and WASP-121 b) that are likely affected by radio quenching, highlighting the importance of considering this effect in target selection for observation campaigns.

Recent observations indicate that the progenitors of globular clusters (GCs) at high redshifts had high average stellar surface densities above <inline-formula><tex-math>$10^5$</tex-math></inline-formula> M<inline-formula><tex-math>$_\odot$</tex-math></inline-formula>pc<inline-formula><tex-math>$^{-2}$</tex-math></inline-formula>. The internal structure and kinematics of the clusters, however, remain out of reach. Numerical simulations are necessary to decipher the origin of spatiokinematic features in present-day GCs. Here we study star cluster formation in a star-by-star hydrodynamical simulation of a low-metallicity starburst in a merger of two gas-rich dwarf galaxies. The simulation accounts for the multiphase interstellar medium, stellar radiation, winds and supernovae, and the accurate small-scale gravitational dynamics near massive stars. We also include prescriptions for stellar collisions and tidal disruption events by black holes. Gravitationally bound star clusters up to <inline-formula><tex-math>$\sim 2\times 10^5$</tex-math></inline-formula> M<inline-formula><tex-math>$_\odot$</tex-math></inline-formula> form dense with initial half-mass radii of <inline-formula><tex-math>$\sim 0.1$</tex-math></inline-formula>─1 pc. The most massive cluster approaches the observed high-redshift surface densities throughout its hierarchical and dissipative assembly. The cluster also hosts a collisionally growing very massive star of <inline-formula><tex-math>$\sim 1000$</tex-math></inline-formula> M<inline-formula><tex-math>$_\odot$</tex-math></inline-formula> that will eventually collapse, forming an intermediate mass black hole. The assembly leaves an imprint in the spatiokinematic structure of the cluster. The youngest stars are more centrally concentrated, they show significant bulk rotation and have radially biased velocity components at outer radii. The older population is more round in shape, rotates slowly, its velocity distribution is isotropic, and exhibits higher dispersion. If chemically enriched star formation proceeds mainly in the later stages of cluster assembly, these results provide a possible explanation for some of the multiple population features observed in dynamically young GCs.

We report the discovery of a long-lasting burst of disk accretion in Cha J11070768-7626326 (Cha 1107-7626), a young, isolated, 5─10 M_Jupiter object. In spectra taken with XSHOOTER at ESO's Very Large Telescope as well as NIRSpec and MIRI on the James Webb Space Telescope, the object transitions from quiescence in 2025 April─May to a strongly enhanced accretion phase in 2025 June─August. The line flux changes correspond to a 6─8-fold increase in the mass accretion rate, reaching 10⁻⁷ M_Jupiteryr⁻¹, the highest measured in a planetary-mass object. During the burst, the Hα line develops a double-peaked profile with redshifted absorption, as observed in stars and brown dwarfs undergoing magnetospheric accretion. The optical continuum increases by a factor of 3─6; the object is ∼1.5─2 mag brighter in the R band during the burst. Mid-infrared continuum fluxes rise by 10%─20%, with clear changes in the hydrocarbon emission lines from the disk. We detect water vapour emission at 6.5─7 μm, which were absent in quiescence. By the end of our observing campaign, the burst was still ongoing, implying a duration of at least 2 months. A 2016 spectrum also shows high accretion levels, suggesting that this object may undergo recurring bursts. The observed event is inconsistent with typical variability in accreting young stars and instead matches the duration, amplitude, and line spectrum of an EXor-type burst, making Cha1107-7626 the first substellar object with evidence of a potentially recurring EXor burst.

Context. We present a methodology for linking the information in the synthetic spectra with the actual information in the simulated models (i.e., their physical properties), in particular to determine where the information resides in the spectra. Aims. We employed a 1D gravitational collapse model with advanced thermochemistry, from which we generated synthetic spectra. We then used neural network emulations and the SHapley Additive exPlanations (SHAP), a machine learning technique, to connect the models' properties to the specific spectral features. Methods. Thanks to interpretable machine learning, we find several correlations between synthetic lines and some of the key model parameters, such as the cosmic-ray ionization radial profile, the central density, or the abundance of various species, suggesting that most of the information is retained in the observational process. Results. Our procedure can be generalized to similar scenarios to quantify the amount of information lost in the real observations. We also point out the limitations for future applicability.

Context. The ongoing discrepancy among Hubble constant (H₀) estimates obtained through local distance ladder methods and early Universe observations poses a significant challenge to the ΛCDM model, suggesting potential new physics. Type II supernovae (SNe II) offer a promising technique for determining H₀ in the Local Universe independently of the traditional distance ladder approach, opening up a complimentary path for testing this discrepancy. Aims. We aim to provide the first H₀ estimate using the tailored expanding photosphere method (EPM) applied to SNe II, made possible by recent advancements in spectral modelling that enhance its precision and efficiency. Methods. Our tailored EPM measurement utilises a spectral emulator to interpolate between radiative transfer models calculated with TARDIS, allowing us to fit SN spectra efficiently and derive self-consistent values for luminosity-related parameters. We applied the method to a set of public data for ten SNe II at redshifts between 0.01 and 0.04. Results. Our analysis demonstrates that the tailored EPM allows us to obtain H₀ measurements with a precision comparable to the most competitive established techniques, even when applied to literature data that are not designed for cosmological applications. We find an independent H₀ value of 74.9 ± 1.9 (stat) km s⁻¹ Mpc⁻¹, which is consistent with most current local measurements. Considering dominant sources of systematic effects, we conclude that our systematic uncertainty is comparable to (or less than) the current statistical uncertainty. Conclusions. This proof-of-principle study highlights the potential of the tailored EPM as a robust and precise tool for investigating the Hubble tension independently of the local distance ladder. Observations of SNe II tailored to H₀ estimations could make this an even more powerful tool by improving the precision and allowing us to improve our understanding of the systematic uncertainties and how to control them.

A commonly employed method to detect protoclusters in the young universe is the search for overdensities of massive star-forming galaxies, such as submillimeter galaxies (SMGs), around high-mass halos, including those hosting quasars. For this work we studied the megaparsec environment surrounding nine physically associated quasar pairs between z = 2.45 and z = 3.82 with JCMT/SCUBA-2 observations at 450 μm and 850 μm covering a field of view of roughly 13.7' in diameter (or 32 Mpc² at the median redshift) for each system. We identified a total of 170 SMG candidates and 26 non-SMG and interloper candidates. A comparison of the underlying 850 μm source models recovered with Monte Carlo simulations to the blank field model reveals galaxy overdensities in all fields, with a weighted average overdensity factor of δ_cumul = 3.4 ± 0.3. From this excess emission at 850 μm, we calculate a star formation rate density of 1700 ± 100 M_⊙ yr⁻¹ Mpc⁻³, consistent with predictions from protocluster simulations and observations. Compared to fields around single quasars, those surrounding quasar pairs have higher excess counts and more centrally peaked star formation, further highlighting the co-evolution of SMGs and quasars. We do not find preferential alignment of the SMGs with the quasar pair direction or their associated Lyα nebulae, indicating that cosmic web filaments on different scales might be traced by the different directions. Overall, this work substantiates the reliability of quasar pairs to detect overdensities of massive galaxies and likely sites of protocluster formation. Future spectroscopic follow-up observations are needed to confirm membership of the SMG candidates with the physically associated quasar pairs and definitively identify the targeted fields as protoclusters.

Dark objects streaming into the solar system can be probed using gravitational wave (GW) experiments through the perturbations that they would induce on the detector test masses. In this work, we study the detectability of the resulting gravitational signal for a number of current and future GW observatories. Dark matter in the form of clumps or primordial black holes with masses in the range <inline-formula><mml:math><mml:msup><mml:mn>10</mml:mn><mml:mn>7</mml:mn></mml:msup><mml:mi>─</mml:mi><mml:msup><mml:mn>10</mml:mn><mml:mn>11</mml:mn></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>g</mml:mi></mml:math></inline-formula> can be detected with the proposed DECIGO experiment.

Parity-odd four-point correlation functions, or trispectra, of cosmic matter density fields provide a unique probe of fundamental symmetries in cosmology. Trispectra of primordial matter density fluctuations produced in the early universe are modified by the subsequent nonlinear structure formation. In this paper, we compute the nonlinear evolution of the parity-odd matter trispectrum to one-loop order, i.e., to third order in density fluctuations, within the framework of effective field theory of the large-scale structure of the universe. By analyzing the different terms in the perturbation series, we demonstrate the structure of infrared divergence cancellations, as required by the equivalence principle. We also derive the forms of the counterterms required to renormalize the ultraviolet divergences. Adopting a specific model for a primordial parity-odd trispectrum, we numerically compute the leading-order effects of nonlinear gravitational evolution and study its impact on baryonic acoustic oscillations within the signal. These calculations are essential for comparing the observed trispectra of nonlinear cosmic density fields with theoretical expectations.

We present and discuss optical emission line properties obtained from the analysis of spectra obtained in the Sloan Digital Sky Survey (SDSS) for an X-ray-selected sample of 3684 galaxies (0.002 < z < 0.55) that were drawn from the eRASS1 catalog. We modeled the SDSS-V DR19 spectra using the NBURSTS full spectrum-fitting technique with E-MILES simple stellar population models and emission line templates to decompose the broad and narrow emission line components for a correlation with the X-ray properties. We placed the galaxies on the Baldwin-Phillips-Terlevich (BPT) diagram to diagnose their dominant excitation mechanism. We show that the consistent use of the narrow component fluxes shifts most galaxies systematically and significantly upward to the active galactic nucleus (AGN) region in the BPT diagram. On this basis, we confirm the dependence of the position of a galaxy in the BPT diagram on its (0.2 − 2.3 keV) X-ray/Hα flux ratio. We also verified the correlation between the X-ray luminosity and the emission line luminosities of the narrow [O III]λ5007 and broad Hα component and the relations between the supermassive black hole mass, the X-ray luminosity, and the velocity dispersion of the stellar component (σ_*) on the base of the unique sample of optical spectroscopic follow-up of X-ray sources detected by eROSITA. These results highlight the importance of emission line decomposition in the AGN classification and refine the connection between X-ray emission and optical emission line properties in galaxies.

We present the implementation of an anisotropic viscosity solver within the magnetohydrodynamics (MHD) framework of the TreeSPH code OpenGadget3. The solver models anisotropic viscous transport along magnetic field lines following the Braginskii formulation and includes physically motivated limiters based on the mirror and firehose instability thresholds, which constrain the viscous stress in weakly collisional plasmas. To validate the implementation, we performed a suite of standard test problems -- including two variants of the sound-wave test, circularly and linearly polarized Alfven waves, fast magnetosonic wave, and the Kelvin-Helmholtz instability -- both with and without the plasma-instability limiters. The results show excellent agreement with the AREPO implementation of a similar anisotropic viscosity model (Berlok et al. 2019), confirming the accuracy and robustness of our method. Our formulation integrates seamlessly within the individual adaptive timestepping framework of OpenGadget3, avoiding the need for subcycling. This provides efficient and stable time integration while maintaining physical consistency. Finally, we applied the new solver to a cosmological zoom-in simulation of a galaxy cluster, demonstrating its capability to model anisotropic transport and plasma microphysics in realistic large-scale environments. Our implementation offers a versatile and computationally efficient tool for studying anisotropic viscosity in magnetized astrophysical systems.

Aims. Plasma shock waves stand out as one of the most promising sites of efficient particle acceleration in extragalactic jets. In electron-ion plasma shocks, electrons can be heated up to large Lorentz factors, making them an attractive scenario to explain the high minimum electron Lorentz factors regularly needed to describe the emission of BL Lac type objects. Still, the (relativistic) thermal electron component is commonly neglected when modelling the observations, although it holds key information on the shock properties. Methods. Considering a shock acceleration scenario, we modelled the broadband emission of the archetypal high synchrotron peaked blazar Markarian 421; we employed particle distributions that included a thermal (relativistic) Maxwellian component at low energies followed by a non-thermal power law, as motivated by particle-in-cell simulations. The observations, in particular in the optical/UV and MeV-GeV bands, efficiently restricted the non-thermal emission from the Maxwellian electrons, which we used to derive constraints on the basic properties, such as the fraction ϵ_e of the total shock energy stored in the non-thermal electrons. Results. The best-fit model yields a non-thermal electron power law with an index of ∼2.4, close to predictions from shock acceleration. Successful fits are obtained when the ratio between the Lorentz factor at which the non-thermal distribution begins (γ_nth) and the dimensionless electron temperature (θ) satisfies γ_nth/θ ≲ 8. Since γ_nth/θ controls ϵ_e, the latter limit implies that at least ϵ_e ≍ 10% of the shock energy is transferred to the non-thermal electrons. These results are almost insensitive to the shock velocity γ_sh, but radio observations indicate γ_sh ≳ 5 since for lower shock velocities the fluxes in the millimetre band are overproduced by the Maxwellian electrons. Therefore, if shocks drive the particle energisation, our findings indicate that they operate in the mildly to fully relativistic regime with efficient electron acceleration. This paper lays the ground for future works, in which we will use plasma simulations to investigate if, and under which conditions, the findings presented here can be reproduced.

Aims. We introduce the Supernovae In a Stratified, Shearing Interstellar medium (SISSI) simulation suite, which aims to enable a more comprehensive understanding of supernova remnants (SNRs) evolving in a complex interstellar medium (ISM) structured by the influence of galactic rotation, gravity, and turbulence. Methods. We utilized zoom-in simulations of 30 SNRs expanding in the self-consistent ISM of a simulated isolated disk galaxy, as the first such simulation achieving sub-parsec resolution in a galactic context. The ISM of the galaxy was resolved down to a maximum resolution of ∼12 pc and we achieved a zoom-in resolution of ∼0.18 pc in the vicinity of the explosion sources. We computed the time evolution of the SNRs' geometry and compared it to the observed geometry of the Local Bubble (LB). Results. During the early stages of evolution (≲1 Myr), SNRs are aptly described by existing analytical models. Afterward, SNRs depart from spherical symmetry, within ∼1% of an orbit, earlier than galactic shear alone predicts, with deformation timescales correlating strongly with local density variations. The minor axis of oblate SNRs is preferably aligned with the galactic poles, while the major axis of prolate SNRs is aligned with galactic rotation, with a pitch angle in the range of 10 − 60°. This result is in agreement with the expectation from galactic shear, suggesting a shear-related origin, such as interactions with shear-deformed substructure. A comparison with the geometry of the LB reveals that it might be slightly younger than the previously estimated ∼14 Myr; otherwise, it exhibits a standard morphology for a SNR of its age and size. Conclusions. Studying the geometry of SNRs can reveal valuable insights about the complex interactions shaping their dynamical evolution. Future studies targeting the geometry of Galactic SNRs can use these insights to obtain a clearer picture of the processes shaping the Galactic ISM.

The Population III.1 theory for supermassive black hole (SMBH) formation predicts a very early ($z\sim20-25$), transient phase, ``The Flash'', of cosmic reionization powered by supermassive stars that are SMBH progenitors. The universe then quickly recombined to become mostly neutral, with this state persisting until galaxies begin to reionize intergalactic gas again at $z\sim 10$. The overall Thomson scattering optical depth, $τ$, from The Flash has been shown to be $τ_{\rm PopIII.1}\sim0.03$, leading to a total $τ\sim0.08-0.09$. Such a value, while significantly larger than that previously inferred from {\it Planck} observations of the low-$l$ $EE$ polarization power spectrum of the CMB, can help relieve several ``tensions'' faced by the standard $Λ$CDM cosmological model, especially the preference for negative neutrino masses and dynamic dark energy. Here we compute $EE$ power spectra of example models of The Flash. We find that, because of its very high redshift, the contribution to $l\lesssim8$ modes is dramatically reduced compared to usual low-$z$ reionization models for the same value of $τ$, while the power at $l\gtrsim8$ is boosted. Thus the Pop III.1 reionization scenario provides a natural way to increase $τ$, while remaining closer to the latest CMB low-$l$ polarization observations.

Context. The baryon fraction of galaxy clusters, expressed as the ratio between the mass in baryons (including both stars and cold or hot gas) and the total mass, is a powerful tool to provide information on the cosmological parameters, while the hot-gas fraction provides indications on the physics of the intracluster plasma and its interplay with the processes that drive galaxy formation. Aims. Using cosmological hydrodynamical simulations of about 300 simulated massive galaxy clusters with a median mass M₅₀₀ ≍ 7 × 10¹⁴ M_⊙ at z = 0, we model the relations between total mass and either baryon fraction or the hot gas fractions at overdensities ∆ = 2500, 500, and 200 with respect to the cosmic critical density, and their evolution from z ∼ 0 to z ∼ 1.3. Methods. We utilized the simulated galaxy clusters from the Three Hundred project, which include star formation and feedback from both supernovae and active galactic nuclei. We fit the simulation results for such scaling relations against three analytic forms (linear, quadratic, and logarithmic in a logarithmic plane) and three forms for the redshift dependence, and we considered as a variable both the inverse of the cosmic scale factor, (1 + z), and the Hubble expansion rate, E(z). Results. We show that power-law dependencies on cluster mass poorly describe the investigated relations. A power law fails to simultaneously capture the flattening of the total baryon and gas fractions at high masses, their drop at low masses, and the transition between these two regimes. The other two functional forms provide a more accurate description of the curvature in mass scaling. The fractions measured within smaller radii exhibit a stronger evolution than those measured within larger radii. Conclusions. From the analysis of these simulations, we evince that as long as we include systems in the mass range herein investigated, the baryon or gas fraction can be accurately related to the total mass through either a parabola or a logarithm in the logarithmic plane. The trends are common to all modern hydro simulations, although the amplitude of the drop at low masses might differ. Being able to observationally determine the gas fraction in groups will thus provide constraints on the baryonic physics.

We present a systematic method for analytically computing time-dependent observables for a relativistic probe particle in Coulomb and Schwarzschild backgrounds. The method generates expressions valid both in the bound and unbound regimes, namely bound-unbound universal expressions. To demonstrate our method we compute the time-dependent radius and azimuthal angle for relativistic motion in a Coulomb background (relativistic Keplerian motion), as well as the electromagnetic field radiated by a relativistic Keplerian source. All of our calculations exhibit bound-unbound universality. Finally, we present an exact expression for the semi-classical wave function in Schwarzschild. The latter is crucial in applying our method to any time-dependent observable for probe-limit motion in Schwarzschild, to any desired order in velocity and the gravitational constant G.

A VLT/MUSE population synthesis study of metallicities in the nuclear star-forming rings of four disk galaxies (NGC 613, NGC 1097, NGC 3351, NGC 7552) is presented. Disentangling the spectral contributions of young and old stellar populations, we find a large spread of ages and metallicities of the old stars in the nuclear rings. This indicates a persistent infall of metal-poor gas and ongoing episodic star formation over many gigayears. The young stars have metallicities a factor two to three higher than solar in all galaxies except NGC 3351, where the range is from half to twice solar. Previously reported detections of extremely metal poor regions at young stellar age on the rings of these four galaxies are a methodological artifact of the average over all stars, young and old. In addition, it is important to include contributions of very young stars ($<6$ Myr) in this environment. For each of the four galaxies, the extinction maps generated through our population synthesis analysis provide support for the infall scenario. They reveal dust lanes along the leading edges of the stellar bars, indicating the flow of interstellar material towards the circumnuclear zone. Prominent stellar clusters show little extinction, most likely because of the onset of stellar winds. Inside and on the nuclear rings, regions that are largely free of extinction are detected.

We present a new class of evolution equations which govern the high-energy behavior of power-suppressed scattering amplitudes. The equations can be viewed as a renormalization group flow with respect to the relevant effective field theory cutoff. A distinct feature of the method is in the use of a multidimensional cutoff to separate the relevant scales in problems characterized by a complex factorization structure. By adjusting the renormalization group variables to the geometry of the effective theory modes, our method naturally extends to a broad spectrum of physical problems including massive, massless, small, and wide angle scattering. We present applications to the benchmark processes of electron-positron forward annihilation and light quark mediated Higgs boson production/decays.

Motivated by recent progress in the spurion analysis of non-invertible selection rules (NISRs) arising from near-group fusion algebras, we further generalize the framework to a class of NISRs obtained from $\mathbb{Z}_2$ orbifolding of a $\mathbb{Z}_M$ symmetry, denoted as $\mathbb{Z}_M/\mathbb{Z}_2$. Many structural features are carried over: for instance, our labeling scheme enables systematic tracking of all couplings when constructing composite amplitudes from simpler building blocks at arbitrary loop orders in perturbation theory. Our analysis provides a transparent understanding of both low-order and all-order zeros of couplings under radiative corrections. Furthermore, we examine the fate of low-order zeros when the fusion algebra is not faithfully realized -- a situation not captured by the vanilla argument of ``loop-induced groupification'' -- and formulate a conjecture on the related aspects of particle decoupling and effective theory. Finally, we discuss the low-order versus all-order zeros in Yukawa textures from the perspective of spurion analysis.

We present BayeSN-TD, an enhanced implementation of the probabilistic type Ia supernova (SN Ia) BayeSN SED model, designed for fitting multiply-imaged, gravitationally lensed type Ia supernovae (glSNe Ia). BayeSN-TD fits for magnifications and time-delays across multiple images while marginalising over an achromatic, Gaussian process-based treatment of microlensing, to allow for time-dependent deviations from a typical SN Ia SED caused by gravitational lensing by stars in the lensing system. BayeSN-TD is able to robustly infer time delays and produce well-calibrated uncertainties, even when applied to simulations based on a different SED model and incorporating chromatic microlensing, strongly validating its suitability for time-delay cosmography. We then apply BayeSN-TD to publicly available photometry of the glSN Ia SN H0pe, inferring time delays between images BA and BC of $ΔT_{BA}=121.9^{+9.5}_{-7.5}$ days and $ΔT_{BC}=63.2^{+3.2}_{-3.3}$ days along with absolute magnifications $β$ for each image, $β_A = 2.38^{+0.72}_{-0.54}$, $β_B=5.27^{+1.25}_{-1.02}$ and $β_C=3.93^{+1.00}_{-0.75}$. Combining our constraints on time-delays and magnifications with existing lens models of this system, we infer $H_0=69.3^{+12.6}_{-7.8}$ km s$^{-1}$ Mpc$^{-1}$, consistent with previous analysis of this system; incorporating additional constraints based on spectroscopy yields $H_0=66.8^{+13.4}_{-5.4}$ km s$^{-1}$ Mpc$^{-1}$. While this is not yet precise enough to draw a meaningful conclusion with regard to the `Hubble tension', upcoming analysis of SN H0pe with more accurate photometry enabled by template images, and other glSNe, will provide stronger constraints on $H_0$; BayeSN-TD will be a valuable tool for these analyses.

In the standard formation models of terrestrial planets in the solar system and close-in super-Earths in nonresonant orbits recently discovered by exoplanet observations, planets are formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas in the final stage. This study aims to theoretically clarify a fundamental scaling law for the orbital architecture of planetary systems formed by giant impacts. In the giant impact stage, protoplanets gravitationally scatter and collide with one another to form planets. Using N-body simulations, we investigate the orbital architecture of planetary systems formed from protoplanet systems by giant impacts. As the orbital architecture parameters, we focus on the mean orbital separation between two adjacent planets and the mean orbital eccentricity of planets in a planetary system. We find that the orbital architecture is determined by the ratio of the two-body surface escape velocity of planets v_esc to the Keplerian circular velocity v_K, k = v_esc/v_K. The mean orbital separation and eccentricity are about 2ka and 0.3k, respectively, where a is the system semimajor axis. With this scaling, the orbital architecture parameters of planetary systems are nearly independent of their total mass and semimajor axis.

The observation of an excess of ttbar production in the threshold region, by CMS and ATLAS, has been interpreted as a toponium contribution, i.e. from below-threshold ttbar virtual states. The news here is the nontrivial experimental extraction of such a signal, not its existence as such. Indeed, already 35+ years ago an NRQCD Green's function approach was used to model the above- and below-threshold production of ttbar pairs in pp/ppbar collisions. The relevant cross section equations from that study are now (re-)implemented in the Pythia 8 event generator. While the above-threshold part is straightforward, the physical interpretation and modelling of below-threshold events is nontrivial, and a final prescription is cross-checked against two simpler ones. Cross sections and some event properties are presented.

Earthshine observations offer a unique opportunity to study Earth as an exoplanet seen from the Moon. As the Sun-Earth-Moon geometry changes, Earth can be observed as a spatially unresolved exoplanet at different phase angles, providing important context for future observations of Earth-like exoplanets. Here, we present a catalog of Earthshine polarization spectra obtained with FORS2 on the VLT, covering diverse scenes, surface conditions, cloud properties, and weather patterns for over a decade. For the first time, we model this extensive dataset in detail using a homogeneous modeling framework. Previous efforts to model some of these spectra struggled to reproduce the observed polarization continuum, even with advanced 3D radiative transfer models incorporating satellite-derived surface and atmospheric data. We improve upon this with a state-of-the-art 3D model that includes subgrid cloud variability, wavelength-dependent surface albedo maps, and an accurate treatment of ocean glint. Our simulations successfully reproduce most observed spectra to a much higher precision than previously possible. Additionally, our statistical analysis reveals that the spectral slope in the visible can distinguish between ocean and mixed surfaces in both reflected and polarized light, which is not possible using broadband filters alone. Polarized light at large phase angles, beyond the Rayleigh scattering regime, is particularly effective in differentiating oceans from land, unlike reflected light. While the vegetation red edge (VRE) is more pronounced in reflectance, it remains detectable in polarization. We also identify correlations between cloud optical thickness and the polarized spectral slope, and between cloud cover and broadband B-R differences in reflected light, demonstrating the diagnostic power of these observations. This catalog and its modeling highlight the potential of polarization for characterizing Earth-like exoplanets. From polarization alone, we can infer oceans, vegetation, and an active water cycle, key indicators of a habitable planet.

We present a first step toward field-level cosmological inference beyond the standard ΛCDM model, focusing on optimizing precision tests in the nonlinear regime of large-scale structure (LSS). As an illustrative case, we study the model-independent "bootstrap" coefficient of the second-order perturbation theory (PT) kernel for matter in real space, which we use as a proxy for new physics effects in the nonlinear sector. We discuss in details the ultraviolet (UV) cutoff dependence induced by discretizing fields on a grid, which requires proper renormalization to eliminate grid artifacts. We formulate a Wilsonian perturbative framework in which the evolution from a UV theory defined at a high cutoff Λ_uv down to lower cutoffs is computed analytically, even beyond the validity of a derivative expansion. Within this framework, we develop an extended version of the GridSPT code incorporating the bootstrap parameterization and demonstrate how cutoff-independent predictions can be achieved through the inclusion of appropriate counterterms. We validate our approach at third- and fifth-order in PT, emphasizing the importance of higher-derivative contributions for unbiased parameter extraction. Our framework is readily extendable to biased tracers and redshift-space distortions.

We present a quantitative spectroscopic study of 13 blue supergiant stars in the Pinwheel Galaxy M101, based on data obtained with the Low Resolution Imaging Spectrometer available at the Keck I telescope. The average stellar metallicity decreases from ∼1.9 Z_⊙ near the center of the galaxy to ∼0.3 Z_⊙ at the optical outskirts. The galactocentric radial metallicity gradient is statistically consistent with previous studies of the gas-phase oxygen abundance from H II regions using the direct method. The H II region-based Cepheid metallicities used by A. G. Riess et al. in their determination of the Hubble constant H₀ are in substantial agreement with our measurements. The direct method gas-phase metallicities of the 18 star-forming galaxies we have analyzed so far, when adjusted upward for a mean ∼0.15 dex oxygen dust depletion factor, are in good agreement with those we infer from the supergiants, over a factor of 50 in metallicity. From the same data, we derive an expression for the metal-dependent depletion of oxygen in photoionized nebulae. Utilizing the flux-weighted gravity–luminosity relationship (FGLR) of blue supergiants, we measure a distance to M101, D = 6.5 ± 0.2 Mpc (μ = 29.06 ± 0.08), which is within 1σ from determinations based on the tip of the red giant branch and Cepheids. With M101 as a nearby Type Ia supernova host and using the observed standardized B-band magnitude of the supernova, our FGLR distance yields an independent value of H₀ = 72.5 ± 4.6 km s^‑1 Mpc^‑1.

We investigate the scaling relation between black hole (BH) and stellar mass (M_∙ − M_*), diagnosing the residual ∆log(M_∙/M_⊙) (∆) in this relation to understand the coevolution of galaxies and BHs in the cosmological hydrodynamic simulation SIMBA. We show that SIMBA reproduces the observed M_∙ − M_* relation well, with little difference between central and satellite galaxies. By using the median value to determine the residuals, we find that the residual correlates with galaxy cold gas content, star formation rate, colour, and BH accretion properties. Both torque and Bondi models implemented in SIMBA contribute to this residual, with torque accretion playing a major role in high-redshift and low-mass galaxies, while Bondi (including BH mergers) dominates at low redshift and massive galaxies. By dividing the sample into two populations (∆ > 0 and ∆ < 0), we compare their evolutionary paths by following the main progenitors. From this evolutionary tracking, we propose a simple picture for BH-galaxy coevolution: early-formed galaxies seed BHs earlier, with stellar mass increasing rapidly to reach the point of triggering 'jet mode' feedback. This process reduces the cold gas content and halts the growth of M_*, effectively quenching galaxies. Meanwhile, during the initial phase of torque accretion growth, the BH mass is comparable between galaxies formed early and those formed later. However, galaxies that formed earlier appear to attain a marginally greater BH mass when transitioning to Bondi accretion, aligning with the galaxy transition time. As the early-formed galaxies reach this point earlier ─ leaving a longer period for Bondi accretion and mergers ─ their residuals become positive, i.e. having more massive BHs at z = 0 compared to these late-formed galaxies at the same M_*. This picture is further supported by the strong positive correlation between the residuals and the galaxy age, which we propose as a validation with observation data of the scenario suggested by SIMBA.

We present analysis of the plateau and late-time phase properties of a sample of 39 Type II supernovae (SNe II) that show narrow, transient, high-ionization emission lines (i.e., "IIn-like") in their early-time spectra from interaction with confined, dense circumstellar material (CSM). Originally presented by W. V. Jacobson-Galán et al., this sample also includes multicolor light curves and spectra extending to late-time phases of 35 SNe with no evidence for IIn-like features at <2 days after first light. We measure photospheric phase light-curve properties for the distance-corrected sample and find that SNe II with IIn-like features have significantly higher luminosities and decline rates at +50 days than the comparison sample, which could be connected to inflated progenitor radii, lower ejecta mass, and/or persistent CSM interaction. However, we find no statistical evidence that the measured plateau durations and ⁵⁶Ni masses of SNe II with and without IIn-like features arise from different distributions. We estimate progenitor zero-age main-sequence (ZAMS) masses for all SNe with nebular spectroscopy through spectral model comparisons and find that most objects, both with and without IIn-like features, are consistent with progenitor masses ≤12.5 M_⊙. Combining progenitor ZAMS masses with CSM densities inferred from early-time spectra suggests multiple channels for enhanced mass loss in the final years before core collapse, such as a convection-driven chromosphere or binary interaction. Finally, we find spectroscopic evidence for ongoing ejecta-CSM interaction at radii >10¹⁶ cm, consistent with substantial progenitor mass-loss rates of ∼10⁻⁴─10⁻⁵ M_⊙ yr⁻¹ (v_w < 50 km s⁻¹) in the final centuries to millennia before explosion.

The direct, empirical determination of the local value of the Hubble constant (H0) has markedly advanced thanks to improved instrumentation, measurement techniques, and distance estimators. However, combining determinations from different estimators is non-trivial, due to correlated calibrations and different analysis methodologies. Using covariance weighting and leveraging the broad and comprehensive community of experts, we constructed a rigorous and transparent Distance Network (DN) to find a consensus value and uncertainty for the local H0. All critically reviewed the available data sets, spanning parallaxes, detached eclipsing binaries, masers, Cepheids, the TRGB, Miras, JAGB stars, SN Ia, Surface Brightness Fluctuations, SN II, the Fundamental Plane, and Tully-Fisher relations and voted for indicators to define a `baseline' DN and others to assess robustness and sensitivity of the results. We provide open-source software and data products to support full transparency and future extensions of this effort. Our conclusions: 1) Local H0 is robustly determined, with first-rank indicators internally consistent within their uncertainties; 2) A covariance-weighted combination yields an uncertainty of 1.1% (baseline) or 0.9% (all estimators); 3) The contribution from SNe Ia is consistent across four current compilations of optical magnitudes or using NIR-only magnitudes; 4) Removing either Cepheids or TRGB has minimal effect; 5) Replacing SNe Ia with galaxy-based indicators changes H0 by less than 0.1 km/s/Mpc, while doubling its uncertainty; 6) The baseline result is H0=73.50+/-0.81 km/s/Mpc. Compared to early Universe results, our result differs by 7.1sigma from flat ΛCDM with Planck+SPT+ACT and 5.0 sigma with BBN+BAO (DESI2). A networked approach is invaluable for enabling further progress in accuracy and precision without overreliance on any single method, sample or group.

We identify a new production channel for quantum chromodynamics (QCD) axions in supernova environments that contributes to axion emissivity for all models solving the strong <inline-formula><mml:math><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math></inline-formula> problem. This channel arises at tree-level from a shift-symmetry-breaking operator constructed at next-to-leading order in chiral perturbation theory. In scenarios where model-dependent derivative couplings to nucleons are absent, this sets the strongest model-independent constraint on the axion mass, improving on existing bounds by two orders of magnitude.

Dusty, submillimeter-selected galaxies without optical counterparts contribute a non-negligible fraction of the star formation in the early universe. However, such a population is difficult to detect through classical optical/UV-based surveys. We report the serendipitous discovery of such an optically dark galaxy, behind the quadruply-lensed $z=2.56$ quasar, H1413+117, offset to the north by 6\arcsec. From $^{12}$CO $J=4$--3, $J=6$--5, and part of the $J=13$--12 transitions, which all spatially coincide with a compact submillimeter continuum emission, we determine an unambiguous spectroscopic redshift, $z=3.386\pm 0.005$. This galaxy has a molecular mass $M_{\rm mol} \sim 10^{11}$ M$_\odot$ and a black hole mass $M_{\rm BH} \sim 10^{8}$ M$_\odot$, estimated from $^{12}$CO $J=4$--3 and archival {\it Chandra} X-ray data ($L_{\rm 2-10,keV} \sim 4 \times 10^{44}$\,erg\,s$^{-1}$), respectively. We also estimate a total infrared luminosity of $L_{\rm FIR} = (2.8\pm{2.3}) \times 10^{12}$ L$_\odot$ and a stellar mass of $M_* \lesssim 10^{11}$ M$_{\odot}$, from spectral energy distribution fitting. According to these simple mass estimations, this gas-rich and X-ray bright galaxy might be in a transition phase from starburst to quasar offering a unique case for studying galaxy-black hole co-evolution under extremely dusty conditions.

The diffuse supernova neutrino background (DSNB) created by stellar core-collapses throughout cosmic history is on the verge of discovery, with SK-Gd showing early deviations from the background expectation and JUNO starting to take data. However, the interpretation of early DSNB data will face significant challenges due to degeneracies between astrophysical parameters and uncertainties in supernova neutrino modeling. We explore how complementary astronomical observations can break these degeneracies and, in this context, we investigate whether early DSNB observations can constrain invisible supernovae, which have no optical emission but are powerful neutrino sources before being swallowed by a forming black hole. Leveraging the differences in the spectra between invisible and visible supernovae, we estimate the sensitivity of 1) detecting the existence of invisible supernovae, and 2) determining the fraction of invisible supernovae. Finally, we discuss how these conclusions depend on the spectral parameters of the black hole-forming component.

Based on the scale-free nature of gravity, the structure in the Universe is expected to be self-similar on large scales. However, this self-similarity eventually breaks down due to small-scale gas physics such as star formation, active galactic nucleus (AGN) and stellar feedback, and non-linear effects gaining importance relative to linear structure formation. In this work, we investigate the large-scale matter flows that connect collapsed structures to their cosmic environments. Specifically, we focus on their agreement with self-similarity in various properties. For this purpose we used the full power of the hydrodynamical cosmological simulation suite Magneticum Pathfinder to precisely calculate the instantaneous inflow and outflow rates of structures on a large range of masses and redshifts. We find a striking self-similarity across the whole mass range and through time that only breaks down in the outflowing regime due to the different outflow driving mechanisms for galaxies versus galaxy clusters. We additionally performed a geometrical analysis of the patterns of inflow versus outflow to demonstrate how the inflows organise into anisotropic filaments driven by the tidal distortions of the environment, while the outflows are fairly isotropic due to their thermal nature. This also manifests in the differences in the thermal and chemical properties of the gas in the inflowing and outflowing component: While the inflowing gas is pristine and colder, encountering the accretion shock surfaces and entering the influence region of AGN and stellar feedback heats the gas up into a diffuse metal-enriched hot atmosphere. Overall the differences between outflowing and infalling gas are enhanced at the galaxy cluster scale compared to the galaxy scale due to the strong accretion shocks that reach out to large radii for these objects. An individual study of the gas motions in the outskirts of one of the most massive clusters in the simulations we carried out demonstrates these results to greater detail: Gas found in the outer (r > 1.2r_vir) hot atmosphere at z = 0 falls in and is completely enriched early in the assembly process before being shock heated and expanding.

Luminosities of pre-main sequence stars evolve during the protoplanetary disc lifetime. This has a significant impact on the heating of their surrounding protoplanetary disks, the natal environments of planets. Moreover, stars of different masses evolve differently. However, this is rarely accounted for in planet formation models. We carry out pebble-driven core accretion planet formation modelling with focus on the impact of pre-main sequence stellar luminosity evolution on giant planet formation around host stars in the range of <inline-formula><tex-math id="TM0001" notation="LaTeX">$1{-}2.4\ \rm M_{\odot }$</tex-math></inline-formula>. We find that giant planet formation is sensitive to the evolution of stellar luminosity, specifically the locations and times at which giant planet formation can occur depend on it. High stellar luminosity causes an increase in the scale height of the gas and pebbles, which may decrease the efficiency of pebble accretion, making it more challenging to form giant planets. This has important consequences for the composition of these giant planets, stressing the need to incorporate such aspects into planet formation models.

The de novo synthesis of life from non-living matter represents a bold scientific challenge, advancing our understanding of life's minimal requirements and offering revolutionary applications in biotechnology. We explore fuel-dependent synthetic cells based on complex coacervate droplets, which lack membranes and readily take up reactants. Given their fuel-dependent nature, these droplets emerge and grow when fuel is abundant but dissolve under starvation conditions, mimicking the non-equilibrium nature of life. However, their ability to produce offspring—a key requirement for life—has remained elusive. Moreover, their rescue in repetitive fueling-starvation experiments has not been demonstrated. Our work elucidates a mechanism of producing offspring by synthetic cells driven by solid-like speckles in droplets liberated as offspring. By fine-tuning parameters, we control offspring number and survival. Finally, refueling sustains second-generation synthetic cells. This system provides a platform for coupling offspring production with self-replicating molecules, paving the way for synthetic cells capable of Darwinian evolution.

Context. The cosmic time evolution of the radial structure is one of the key topics in the investigation of disc galaxies. In the build-up of galactic discs, gas infall is an important ingredient and it produces radial gas inflows as a physical consequence of angular momentum conservation since the infalling gas onto the disc at a specific radius has lower angular momentum than the circular motions of the gas at the point of impact. NGC 300 is a well-studied isolated, bulgeless, and low-mass disc galaxy ideally suited for an investigation of galaxy evolution with radial gas inflows. Aims. Our aim is to investigate the effects of radial gas inflows on the physical properties of NGC 300, for example the radial profiles of HI gas mass and star formation rate (SFR) surface densities, specific star formation rate (sSFR), and metallicity, and to study how the metallicity gradient evolves with cosmic time. Methods. A chemical evolution model for NGC 300 was constructed by assuming its disc builds up progressively by the infalling of metal-poor gas and the outflowing of metal-enriched gas. Radial gas inflows were also considered in the model. We used the model to build a bridge between the available data (e.g. gas content, SFR, and chemical abundances) observed today and the galactic key physical processes. Results. Our model including the radial gas inflows and an inside-out disc formation scenario can simultaneously reproduce the present-day observed radial profiles of HI gas mass surface density, SFR surface density, sSFR, gas-phase, and stellar metallicity. We find that, although the value of radial gas inflow velocity is as low as ‑0.1 km s^‑1, the radial gas inflows steepen the present-day radial profiles of HI gas mass surface density, SFR surface density, and metallicity, but flatten the radial sSFR profile. Incorporating radial gas inflows significantly improves the agreement between our model predicted present-day sSFR profile and the observations of NGC 300. Our model predictions are also in good agreement with the star-forming galaxy main sequence and the mass-metallicity relation of star-forming galaxies. It predicts a significant flattening of the metallicity gradient with cosmic time. We also find that the model predicted star formation has been more active recently, indicating that the radial gas inflows may help to sustain star formation in local spirals, at least in NGC 300.

The dispersion measure (DM) of fast radio bursts (FRBs) is sensitive to the electron distribution in the Universe, making it a promising probe of cosmology and astrophysical processes such as baryonic feedback. However, cosmological analyses of FRBs require knowledge of the contribution to the observed DM coming from the FRB host. The size and distribution of this contribution is still uncertain, thus significantly limiting current cosmological FRB analyses. In this study, we extend the baryonification (BCM) approach to derive a physically-motivated, analytic model for predicting the host contribution to FRB DMs. By focusing on the statistical properties of FRB host DMs, we find that our simple model is able to reproduce the probability distribution function (PDF) of host halo DMs measured from the CAMELS suite of hydrodynamic simulations, as well as their mass- and redshift dependence. Furthermore, we demonstrate that our model allows for self-consistent predictions of the host DM PDF and the matter power spectrum suppression due to baryonic effects, as observed in these simulations, making it promising for modelling host-DM-related systematics in FRB analyses. In general, we find that the shape of the host DM PDF is determined by the interplay between the FRB and gas distributions in halos. Our findings indicate that more compact FRB profiles require shallower gas profiles (and vice versa) in order to match the observed DM distributions in hydrodynamic simulations. Furthermore, the analytic model presented here shows that the shape of the host DM PDF is highly sensitive to the parameters of the BCM. This suggests that this observable could be used as an interesting test bed for baryonic processes, complementing other probes due to its sensitivity to feedback on galactic scales. We further discuss the main limitations of our analysis, and point out potential avenues for future work.

We present a global neutrino oscillation analysis of models with a single large extra dimension in which right-handed neutrinos possess bulk Dirac masses. Two scenarios are considered: large extra dimensions with bulk masses and the dark dimension framework, both predicting a tower of sterile Kaluza-Klein states that mix with active neutrinos. Using data from MINOS/MINOS+, KamLAND, and Daya Bay, we perform a joint likelihood analysis. No signatures of these theories were found. Therefore, we constrain the compactification radius under different bulk mass and Yukawa coupling assumptions. Large positive bulk masses or sizable Yukawas lead to strong bounds, while small couplings or negative bulk masses remain less constrained.

We study ultralight scalar fields with quadratic couplings to Standard-Model fermions and derive strong constraints from white-dwarf mass-radius data. Such couplings source scalar profiles inside compact stars, shift fermion masses, and can produce a new ground state of matter. We analyze couplings to electrons and to nucleons, incorporating composition and finite-temperature effects in white dwarf structure and equations of state. We identify two robust observables: (i) forbidden gaps - ranges of radii with no stable configurations - and (ii) characteristic shape distortions that drive white dwarf masses toward the Chandrasekhar limit (electron couplings) or shift the maximum mass (nucleon couplings). Confronting these predictions with precise measurements for Sirius B and Procyon B, together with the global white dwarf population, excludes large regions of unexplored parameter space and extends earlier QCD-axion-specific bounds to a broader class of scalar theories. Our stellar constraints rely only on sourcing and do not assume the scalar constitutes dark matter; where mass reductions are small, precision laboratory searches remain competitive. White-dwarf astrophysics thus provides a powerful, largely assumption-minimal probe of ultralight, quadratically coupled scalars.

Cross-correlations techniques offer an alternative method to search for molecular species in JWST observations of exoplanet atmospheres. In a previous article, we applied cross-correlation functions for the first time to JWST NIRSpec/G395H observations of exoplanet atmospheres, resulting in a detection of CO in the transmission spectrum of WASP-39b and a tentative detection of CO isotopologues. Here we present an improved version of our cross-correlation technique and an investigation into how efficient the technique is when searching for other molecules in JWST NIRSpec/G395H data. Our search results in the detection of more molecules via cross-correlations in the atmosphere of WASP-39b, including $\rm H_{2}O$ and $\rm CO_{2}$, and confirms the CO detection. This result proves that cross-correlations are a robust and computationally cheap alternative method to search for molecular species in transmission spectra observed with JWST. We also searched for other molecules ($\rm CH_{4}$, $\rm NH_{3}$, $\rm SO_{2}$, $\rm N_{2}O$, $\rm H_{2}S$, $\rm PH_{3}$, $\rm O_{3}$ and $\rm C_{2}H_{2}$) that were not detected, for which we provide the definition of their cross-correlation baselines for future searches of those molecules in other targets. We find that that the cross-correlation search of each molecule is more efficient over limited wavelength regions of the spectrum, where the signal for that molecule dominates over other molecules, than over broad wavelength ranges. In general we also find that Gaussian normalization is the most efficient normalization mode for the generation of the molecular templates.

Supermassive black hole feedback is the currently favoured mechanism to regulate the star formation rate of galaxies and prevent the formation of ultra-massive galaxies (M_⋆ > 10¹² M_⊙). However, the mechanism through which the outflowing energy is transferred to the surrounding medium strongly varies from one galaxy evolution model to another, such that a unified model for active galactic nucleus (AGN) feedback does not currently exist. The hot atmospheres of galaxy groups are highly sensitive laboratories of the feedback process, as the injected black hole energy is comparable to the binding energy of halo gas particles. Here we report multi-wavelength observations of the fossil galaxy group SDSSTG 4436. The hot atmosphere of this system exhibits a highly relaxed morphology centred on the giant elliptical galaxy NGC 3298. The X-ray emission from the system features a compact core (< 10 kpc) and a steep increase in the entropy and cooling time of the gas, with the cooling time reaching the age of the Universe ∼15 kpc from the centre of the galaxy. The observed entropy profile implies a total injected energy of ∼1.5 × 10⁶¹ ergs, which given the high level of relaxation could not have been injected by a recent merging event. Star formation in the central galaxy NGC 3298 is strongly quenched and its stellar population is very old (∼10.6 Gyr). The currently detected radio jets have low power and are confined within the central compact core. All the available evidence implies that this system was affected by giant AGN outbursts that raised the entropy of the neighbouring gas to the point that the gas no longer efficiently cools. Our findings imply that AGN outbursts can be energetic enough to unbind gas particles and lead to the disruption of cool cores.

We present a view of the stellar halo in the inner-central regions of the Milky Way (R ≲ 10 kpc) mapped by RR Lyrae stars. The combined BRAVA-RR/APOGEE RR Lyrae catalog is used to obtain a sample of 281 RR Lyrae stars located in the bulge region of the Galaxy, but with orbits indicating they belong to the inner-central halo. The RR Lyrae stars in the halo are more metal-poor than the bulge RR Lyrae stars and have pulsation properties more consistent with an accreted population. We use the Milky Way-like zoom-in cosmological simulation Auriga to compare the properties of the RR Lyrae stars to those expected from the "Gaia-Enceladus-Sausage" (GES) merger. The integrals of motions and eccentricities of the RR Lyrae stars are consistent with a small fraction of 6–9% ± 2% of the inner-central halo RR Lyrae population having originated from GES. This fraction, lower than what is seen in the solar neighborhood, is consistent with trends seen in the Auriga simulation, where a GES-like merger would have a decreasing fraction of GES stars at small Galactocentric radii compared to other accreted populations. Very few of the Auriga inner Galaxy GES-18 particles have properties consistent with belonging to a bulge population with (z_max < 1.1 kpc), indicating that no (or very few) RR Lyrae stars with bulge orbits should have originated from GES.

Gravitational-wave (GW) neutron star mergers with an associated electromagnetic counterpart constitute powerful probes of binary evolution, the production sites of heavy elements, general relativity, and the expansion of the Universe. Only a handful of candidate GW binary mergers during the fourth LIGO/Virgo/KAGRA observing run (O4) so far are believed to include a neutron star. We present optical–near-infrared follow-up observations of the candidate neutron star–black hole GW merger S250206dm. This is the first high-significance mass-gap neutron star–black hole candidate observed by multiple GW detectors (thus having a significantly smaller sky localization than one-detector events), offering the first opportunity to effectively follow up a GW event of this kind. Our GW MultiMessenger Astronomy DECam Survey (GW-MMADS) campaign consisted of a wide-field search using the Dark Energy Camera (DECam) and T80-South (T80S), as well as galaxy-targeted observations using the Southern Astrophysical Research (SOAR) imager and the Fraunhofer Telescope at Wendelstein Observatory. No viable kilonova counterpart was found in our observations. We use our observation depths to place competitive constraints on kilonova models similar to or brighter than the GW170817 kilonova AT 2017gfo within our observed fields, ruling out 100% of such models with SOAR galaxy-targeted observations and ∼43% (48%) with DECam (DECam and T80S).

Extended <inline-formula><tex-math>$\mathrm{Ly\,\,\alpha }$</tex-math></inline-formula> emission is commonly observed around star-forming galaxies, opening a window for probing the neutral hydrogen gas in the circumgalactic medium (CGM). In this paper, we develop a prescription of spherically symmetric CGM gas properties and build emulators to model circularly averaged surface brightness (SB) profiles of the extended <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> emission. With CGM gas properties parametrized by the density, velocity and temperature profiles, a self-shielding calculation is carried out to obtain the neutral gas distribution with ionizing photons from the ultraviolet (UV) background and star formation in the galaxy. Our calculation reveals three types of systems with distinct neutral gas distribution: non-shielded systems with the CGM being highly ionized across all radii, shielded systems with a neutral gas shell shielding the UV background, and transitional systems in between. <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> SB profiles are obtained through <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> radiative transfer (RT) simulations, performed for the CGM models with three kinds of <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> sources: the star formation from central and satellite galaxies, and the recombination in the CGM. We build emulators to efficiently predict <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> SB profiles for given model parameters and <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> sources, based on Gaussian process regression. After being trained with only 180 RT simulations for each <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> source, the emulators reach an overall accuracy at the level of <inline-formula><tex-math>$\sim 20$</tex-math></inline-formula> per cent. By applying the emulators to fit mock <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> SB profiles constructed from our model, we find a reasonable recovery of model parameters, indicating the potential of extracting physical information of the CGM and galaxies from the observed extended <inline-formula><tex-math>$\mathrm{Ly\,\alpha }$</tex-math></inline-formula> emission.

Active galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard-X-ray-selected (14–195 keV) nearby (z < 0.1) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that, while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios (0.01–1), this dependence vanishes for sources with lower Eddington ratios (<0.01). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.

Multiply-imaged supernovae (SNe) provide a novel means of constraining the Hubble constant ($H_0$). Such measurements require a combination of precise models of the lensing mass distribution and an accurate estimate of the relative time delays between arrival of the multiple images. Only two multiply-imaged SNe, Refsdal and H0pe, have enabled measurements of $H_0$ thus far. Here we detail the third such measurement for SN Encore, a $z=1.95$ SNIa discovered in JWST/NIRCam imaging. We measure the time delay, perform simulations of additional microlensing and millilensing systematics, and combine with the mass models of Suyu et al. in a double-blind analysis to obtain our $H_0$ constraint. Our final time-delay measurement is $Δt_{1b,1a}=-39.8_{-3.3}^{+3.9}$ days, which is combined with seven lens models weighted by the likelihood of the observed multiple image positions for a result of $H_0=66.9_{-8.1}^{+11.2} \rm{km} \rm{s}^{-1}\rm{Mpc}^{-1}$. The uncertainty on this measurement could be improved significantly if template imaging is obtained. Remarkably, a sibling to SN Encore (SN "Requiem") was discovered in the same host galaxy, making the MACS J0138.0-2155 cluster the first system known to produce more than one observed multiply-imaged SN. SN Requiem has a fourth image that is expected to appear within a few years, providing an unprecedented decade-long baseline for time-delay cosmography and an opportunity for a high-precision joint estimate of $H_0$.

Multiple photometric studies have reported the presence of seemingly older accreting pre-main sequence stars (PMS) in optical colour-magnitude diagrams (CMDs). We investigate this phenomenon in the Orion Nebula, which harbors a subset of stars that show infrared excess detected by Spitzer and Halpha excess emission, yet display significantly older isochronal ages (>10 Myr) compared to the bulk population (~1-3 Myr) in the r, (r-i) CMD. We perform a detailed spectroscopic analysis of 40 Orion Nebula stars using VLT/X-Shooter, covering CMD-based isochronal ages from 1 to over 30 Myr. We derive extinction values, stellar properties, and accretion parameters by modeling the ultraviolet excess emission through a multicomponent fitting procedure. The sample spans spectral types from M4.5 up to K6, and masses in the range ~0.1-0.8 Msun. We demonstrate that, when extinction and, most importantly, accretion effects are accurately constrained, the stellar luminosity and effective temperature of the majority of the seemingly old stars become consistent with a younger population (~1-5 Myr). This is supported by strong lithium absorption, which corroborates their youth, and by the accretion-to-stellar luminosity ratios typical for young, accreting stars. Three of these sources, however, remain old even after our analysis, despite showing signatures consistent with ongoing accretion from a protoplanetary disc. More generally, our analysis indicates that excess continuum emission from accretion shocks affects the placement of PMS stars in the CMD, displacing sources towards bluer optical colours. This study highlights the critical role of accretion in shaping the stellar properties estimates (including age) derived from optical CMDs and emphasizes the need to carefully account for accretion effects when interpreting age distributions in star-forming regions.

Earthshine observations offer a unique opportunity to study Earth as an exoplanet seen from the Moon. As the Sun-Earth-Moon geometry changes, Earth can be observed as a spatially unresolved exoplanet at different phase angles, providing important context for future observations of Earth-like exoplanets. Here, we present a catalog of Earthshine polarization spectra obtained with FORS2 on the VLT, covering diverse scenes, surface conditions, cloud properties, and weather patterns for over a decade. For the first time, we model this extensive dataset in detail using a homogeneous modeling framework. Previous efforts to model some of these spectra struggled to reproduce the observed polarization continuum, even with advanced 3D radiative transfer models incorporating satellite-derived surface and atmospheric data. We improve upon this with a 3D model that includes subgrid cloud variability, wavelength-dependent surface albedo maps, and an accurate treatment of ocean glint. Our simulations successfully reproduce most observed spectra to a much higher precision than previously possible. Our statistical analysis reveals that the spectral slope in the visible can distinguish between ocean and mixed surfaces in both reflected and polarized light, which is not possible using broadband filters alone. Polarized light at large phase angles, beyond the Rayleigh scattering regime, is particularly effective in differentiating oceans from land, unlike reflected light. We also identify correlations between cloud optical thickness and the polarized spectral slope, and between cloud cover and broadband B-R differences in reflected light, demonstrating the diagnostic power of these observations. This work highlight the potential of polarization for characterizing Earth-like exoplanets. From polarization alone, we can infer oceans, vegetation, and an active water cycle, key indicators of a habitable planet.

We study magnetic conversion of ultra-relativistic axion-like particles (ALPs) into photons in compact-star environments, focusing on the hot, transient conditions of core-collapse supernova (SN) remnants and neutron-star mergers (NSMs). We address previously overlooked uncertainties, particularly the suppression caused by ejected matter near the stellar surface, a region crucial to the conversion process. We derive analytical expressions for the transition rate; they reveal the influence of key parameters and their uncertainties. We update constraints using historical gamma-ray data from SN~1987A and find $g_{aγ}<5\times10^{-12}~{\rm GeV}^{-1}$ for $m_a\lesssim10^{-9}$ meV. We also forecast sensitivities for a future Galactic SN and for NSMs, assuming observations with Fermi-LAT or similar gamma-ray instruments. We distinguish ALPs -- defined as coupling only to photons and produced via Primakoff scattering -- from axions, which also couple to nucleons and emerge through nuclear bremsstrahlung. We omit pionic axion production due to its large uncertainties and inconsistencies, though it could contribute comparably to bremsstrahlung under optimistic assumptions. For the compact sources, we adopt time-averaged one-zone models, guided by numerical simulations, to enable clear and reproducible parametric studies.

The age of the Local Bubble (LB) can be used to constrain the timescales, on which the interstellar medium in the solar neighborhood is evolving. Previous estimates have put the age of the LB at $\gtrsim 14\,\text{Myr}$, and suggested that its expansion was powered by $\sim 15-20$ SNe, yet in a companion paper we have seen hints that this age might be too high. Following up on these hints, we aim to place new constraints on the age of the LB. We reconstruct the geometry and momentum of the LB using publicly available 3D dust maps to compare its geometry to that of the high-quality sample of simulated supernova remnants in the SISSI project. We find that, in contrast to previous estimates, $\gtrsim 20$ SNe over $\sim 4\,\text{Myr}$ are required to explain both the momentum and the size of the LB. The julia source-code for our analysis is made available at doi.org/10.5281/zenodo.17054923. Previous estimates of the age of the LB have seemingly overestimated its age and underestimated the number of SNe powering its expansion. Our results are in tension with the assumption that the LB is powered solely by SNe associated with the nearby Scorpius-Centraurus OB association, which appears to have stopped forming stars at about the same time as the LB began to expand. In light of this new evidence, our results cast serious doubts on the claim that star formation in the solar neighborhood was driven by the expansion of the LB, and might have instead quenched it.

Fast neutrino flavor conversion may impact the explosion mechanism and nucleosynthesis in core-collapse supernovae. A necessary condition for fast flavor conversion is the presence of crossings in the angular distribution of the electron-neutrino lepton number (ELN) crossing. Because of the computational costs, flavor-dependent angular distributions are not computed by the vast majority of state-of-the-art hydrodynamical simulations; instead, angular distributions are reconstructed employing approximate methods in postprocessing. In this work, we evaluate the performance of four methods adopted to diagnose the existence of ELN crossings. For selected postbounce times, we extract the fluid and thermodynamic properties from spherically symmetric supernova simulations for an <inline-formula><mml:math><mml:mrow><mml:mn>18.6</mml:mn><mml:msub><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mrow><mml:mo>⊙</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> progenitor, testing cases with and without muons as well as with and without mixing-length treatment of protoneutron star convection. We compare the occurrence of crossings in the angular distributions obtained by solving the Boltzmann equations with those in distributions reconstructed from angular moments of our Boltzmann solutions by using the maximum entropy and Minerbo schemes, and also with crossings identified via a polynomial weighting function applied to the angular moments. Our results show that the polynomial method and the Minerbo closure scheme have severe limitations. The maximum entropy approach captures most of the forward crossings, although it fails to reproduce or misidentifies crossings in a subset of our models. These findings highlight the need for robust modeling of the neutrino angular properties in order to assess the impact of flavor conversion on the supernova mechanism.

The origin of the high-<inline-formula><tex-math>$\alpha$</tex-math></inline-formula> component of the Galactic bulge remains debated, unlike the bar-driven origin of the low-<inline-formula><tex-math>$\alpha$</tex-math></inline-formula> bulge. We examine the metallicity-dependent dynamical properties of high-[Mg/Fe] stars in the bar region, using samples of low- and high-[Mg/Fe] stars from APOGEE DR17, complemented by the PIGS catalogue of <inline-formula><tex-math>${\rm [Fe/H]}&lt; -1$</tex-math></inline-formula> stars. The mean Galactocentric rotational velocity <inline-formula><tex-math>$\overline{V}_{\phi }(R)$</tex-math></inline-formula> is nearly cylindrical for both low- and high-[Mg/Fe] stars across the bulge and outer bar. <inline-formula><tex-math>$\overline{V}_{\phi }(R)$</tex-math></inline-formula> of high-[Mg/Fe] stars with <inline-formula><tex-math>${\rm [Fe/H]}\ge -0.6$</tex-math></inline-formula> is similar within errors to low-[Mg/Fe] stars in the bulge, and 10–20 per cent lower in the outer bar. The mean radial velocity field of these stars exhibits a quadrupole pattern similar to low-[Mg/Fe] stars. Integrating orbits in realistic barred Galactic potentials, these model-independent properties correspond to a peanut bulge in the orbital density distributions for high-[Mg/Fe] stars with <inline-formula><tex-math>${\rm [Fe/H]}\ge -0.6$</tex-math></inline-formula>, transitioning toward a more spheroidal structure at lower metallicities. Additionally, <inline-formula><tex-math>$\overline{V}_{\phi }({\rm [Fe/H]})$</tex-math></inline-formula> for stars increases steeply as metallicity increases from about [Fe/H] <inline-formula><tex-math>$\sim -1.3$</tex-math></inline-formula>, resembling the spin-up observed at larger Galactic radii. This is accompanied by a transition in the dominant orbit families, from co- and counter-rotating <inline-formula><tex-math>${\rm cloud\, A}$</tex-math></inline-formula> and <inline-formula><tex-math>${\rm x_4}$</tex-math></inline-formula> orbits at low metallicities to co-rotating bar-supporting <inline-formula><tex-math>${\rm x_1}$</tex-math></inline-formula> family tree, <inline-formula><tex-math>${\rm box}$</tex-math></inline-formula>, and <inline-formula><tex-math>${\rm cloud\, A}$</tex-math></inline-formula> orbits at solar metallicity. Our results strengthen the case that the bulk of the high-[Mg/Fe] component in the bar region evolved from an <inline-formula><tex-math>$\alpha$</tex-math></inline-formula>-enhanced disc, while metal-poor stars with <inline-formula><tex-math>${\rm [Fe/H]}&lt; -1$</tex-math></inline-formula> trace a more turbulent origin.

We present new observations that densely sample the microwave (4-360 GHz) continuum spectra from eight young systems in the Taurus region. Multi-component, empirical model prescriptions were used to disentangle the contributions from their dust disks and other emission mechanisms. We found partially optically thick, free-free emission in all these systems, with positive spectral indices (median at 10 GHz) and contributing 5-50% of the 43 GHz fluxes. There is no evidence for synchrotron or spinning dust grain emission contributions for these targets. The inferred dust disk spectra all show substantial curvature: their spectral indices decrease with frequency, from -4.0 around 43 GHz to 1.7-2.1 around 340 GHz. This curvature suggests that a substantial fraction of the (sub)millimeter ( ≳ 200 GHz) dust emission may be optically thick, and therefore the traditional metrics for estimating dust masses are flawed. Assuming the emission at lower frequencies (43 GHz) is optically thin, the local spectral indices and fluxes were used to constrain the disk-averaged dust properties and estimate corresponding dust masses. These masses are roughly an order of magnitude higher ( ≈1000M⊕) than those found from the traditional approach based on (sub)millimeter fluxes. These findings emphasize the value of broad spectral coverage - particularly extending to lower frequencies ( ∼cm-band) - for accurately interpreting dust disk emission; such observations may help reshape our perspective on the available mass budgets for planet formation.

Mean-field dynamo theory, describing the evolution of large-scale magnetic fields, has been the mainstay of theoretical interpretation of magnetism in astrophysical objects such as the Sun for several decades. More recently, three-dimensional magnetohydrodynamic simulations have reached a level of fidelity where they capture dynamo action self-consistently on local and global scales without resorting to parametrization of unresolved scales. Recent global simulations also capture many of the observed characteristics of solar and stellar large-scale magnetic fields and cycles. Successful explanation of the results of such simulations with corresponding mean-field models is a crucial validation step for mean-field dynamo theory. Here the connections between mean-field theory and current dynamo simulations are reviewed. These connections range from the numerical computation of turbulent transport coefficients to mean-field models of simulations, and their relevance to the solar dynamo. Finally, the most notable successes and current challenges in mean-field theoretical interpretations of simulations are summarized.

Broad absorption line (BAL) quasars are often considered X-ray weak relative to their optical/UV luminosity, whether intrinsically (i.e. the coronal emission is fainter) or due to large column densities of absorbing material. The SDSS-V is providing optical spectroscopy for samples of quasar candidates identified by eROSITA as well as Chandra, XMM, or Swift, making the resulting data sets ideal for characterizing the BAL quasar population within an X-ray selected sample. We use the Balnicity Index (BI) to identify the BAL quasars based on absorption of the C IV<inline-formula><tex-math>$\lambda \, 1549$</tex-math></inline-formula> emission line in the optical spectra, finding 143 BAL quasars in our sample of 2317 X-ray selected quasars within <inline-formula><tex-math>$1.5\le z \le 3.5$</tex-math></inline-formula>. This observed BAL fraction of <inline-formula><tex-math>$\approx$</tex-math></inline-formula> 6 per cent is comparable to that found in optically selected samples. We also identify absorption systems via the Absorption Index (AI) which includes mini-BALs and NALs, finding 954 quasars with AI <inline-formula><tex-math>$&gt;0$</tex-math></inline-formula>. We consider the C IV emission space (equivalent width versus blueshift) to study the BAL outflows within the context of the radiatively driven accretion disc–wind model. X-ray selection excludes the highest outflow velocities in emission but includes the full range of absorption velocities which we suggest is consistent with the BAL gas being located further from the X-ray corona than the emitting gas. We observe both X-ray weak and X-ray strong BALs (via the optical-to-X-ray spectral slope, <inline-formula><tex-math>$\alpha _\text{ox}$</tex-math></inline-formula>) and detect little evidence for differing column densities between the BAL and non-BAL quasars, suggesting the BALs and non-BALs have the same shielding gas and intrinsic X-ray emission.

As the mathematical capabilities of large language models (LLMs) improve, it becomes increasingly important to evaluate their performance on research-level tasks at the frontier of mathematical knowledge. However, existing benchmarks are limited, as they focus solely on final-answer questions or high-school competition problems. To address this gap, we introduce IMProofBench, a private benchmark consisting of 39 peer-reviewed problems developed by expert mathematicians. Each problem requires a detailed proof and is paired with subproblems that have final answers, supporting both an evaluation of mathematical reasoning capabilities by human experts and a large-scale quantitative analysis through automated grading. Furthermore, unlike prior benchmarks, the evaluation setup simulates a realistic research environment: models operate in an agentic framework with tools like web search for literature review and mathematical software such as SageMath. Our results show that current LLMs can succeed at the more accessible research-level questions, but still encounter significant difficulties on more challenging problems. Quantitatively, Grok-4 achieves the highest accuracy of 52% on final-answer subproblems, while GPT-5 obtains the best performance for proof generation, achieving a fully correct solution for 22% of problems. IMProofBench will continue to evolve as a dynamic benchmark in collaboration with the mathematical community, ensuring its relevance for evaluating the next generation of LLMs.

Generally, merger likelihood increases in denser environments; however, the large relative velocities at the centres of dense clusters are expected to reduce the likelihood of mergers for satellite galaxies. Tidal features probe the recent merger histories of galaxies. The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will produce an unprecedented sample of tidal features around millions of galaxies. We use LSST-like mock observations of galaxies at $z\sim0$ from the EAGLE, IllustrisTNG and Magneticum Pathfinder cosmological-hydrodynamical simulations to predict the occurrence rates of tidal features around satellite galaxies across group and cluster environments in the velocity-radius projected phase-space diagram to investigate the impact of these environments on tidal feature occurrence. We find that ancient infallers in the projected phase-space exhibit a decreasing tidal feature fraction with increasing halo mass, whereas recent infallers in the projected phase-space show unchanging tidal feature fractions with halo mass. Our results show, for the first time in cosmological simulations, a suppression of tidal feature fractions in the central regions of galaxy clusters, indicating a reduced merger rate due to higher cluster-centric velocities and lower galaxy total masses in the cluster centres. Using a toy model, we show that the presence of more tidal features in the recent infaller zone and cluster outskirts suggests that tidal features occur in interactions within infalling groups and dissipate by the time they are ancient infallers, indicating a $\lesssim3\pm2$ Gyr survival time of tidal features within clusters.

One of the most puzzling properties of the high-redshift AGN population recently discovered by JWST, including both broad-line and narrow-line sources, is their X-ray weakness. With very few exceptions, and regardless of the optical classification, they are undetected at the limits of the deepest Chandra fields, even when stacking signals from tens of sources in standard observed-frame energy intervals (soft, hard, and full bands). It has been proposed that their elusive nature in the X-ray band is due to heavy absorption by dust-free gas or intrinsic weakness, possibly due to high, super-Eddington accretion. In this work, we perform X-ray stacking in three customized rest-frame energy ranges (1-4, 4-7.25, and 10-30 keV) of a sample of 50 Type 1 and 38 Type 2 AGN identified by JWST in the CDFS and CDFN fields. For the Type 2 sub-sample, we reach a total of about 210 Ms exposure, and we report a significant ($\sim 3σ$) detection in the hardest (10-30 keV rest frame) band, along with relatively tight upper limits in the rest frame softer energy bands. The most straightforward interpretation is in terms of heavy obscuration due to gas column densities well within the Compton thick regime ($> 2 \times 10^{24} $cm$^{-2}$) with a large covering factor, approaching 4$π$. The same procedure applied to the Type 1 sub-sample returns no evidence for a significant signal in about 140 Ms stacked data in any of the adopted bands, confirming their surprisingly elusive nature in the X-ray band obtained with previous stacking experiments. A brief comparison with the current observations and the implications for the evolution of AGN are discussed.

Stellar shells and streams are remnants of satellite galaxies visible around galaxies. Advances in low-surface-brightness observations and increasing resolution of cosmological simulations now allow investigating the properties and origin of these features. The metallicity, age, and velocity dispersion of shells and streams are investigated to infer their progenitor galaxies properties. We employed the hydrodynamical cosmological simulations Magneticum Pathfinder to extract these properties and identify the progenitors of the shells and streams. We compared to observational results from surveys and individual galaxies, matching and testing the methodology used in observations. Mock observations of shells and streams agree well with observational data regarding their morphology and spatial distribution. We find that both types of features are associated with localized depressions in stellar velocity dispersion compared to the surrounding regions. They are not as clearly distinct in metallicity and ages, though overall shells and more metal rich and streams are younger. We confirm results from idealized models that shells form commonly from radial major mergers but also through minor mergers, while streams usually form from minor mergers on circular orbits. We do not find the widths of streams to correlate with the half-mass radii of their progenitors, but the progenitors follow the mass-metallicity relation. On average, the masses measured for shells and streams approximately corresponds to 20% of the progenitor mass. We introduce a class of star-forming streams, which originate from in-situ star formation rather than the disruption of a satellite galaxy. Measuring stellar population properties of shells and streams provides the means to reconstruct the progenitor properties, and especially distinguish those streams that are not made through the disruption of a galaxy but formed in-situ.

Aims. We investigate the role of cosmic ray (CR) halos in shaping the physical properties of starburst-driven galactic outflows. Methods. We constructed a model for galactic outflows driven by a continuous central injection of energy, gas, and CRs, where the treatment of CRs accounts for the effect of CR pressure gradients on the flow dynamics. The model parameters were set by the effective properties of a starburst. By analyzing the asymptotic behavior of our model, we derived the launching criteria for starburst-driven galactic outflows and determined their corresponding outflow velocities. Results. We find that in the absence of CRs, stellar feedback can only launch galactic outflows if the star formation rate (SFR) surface density exceeds a critical threshold proportional to the dynamical equilibrium pressure. In contrast, CRs can always drive slow outflows. Outflows driven by CRs dominate in systems with SFR surface densities below the critical threshold, but their influence diminishes in highly star-forming systems. However, in older systems with established CR halos, the CR contribution to outflows weakens once the outflow reaches the galactic scale height, making CRs ineffective in sustaining outflows in such environments. Conclusions. Over cosmic time, galaxies accumulate relic CRs in their halos, providing additional non-thermal pressure support that suppresses low-velocity CR-driven outflows. We predict that such low-velocity outflows are expected only in young systems that have yet to build significant CR halos. In contrast, fast outflows in starburst galaxies, where the SFR surface density exceeds the critical threshold, are primarily driven by thermal energy and remain largely unaffected by CR halos.

Context. The dust-to-gas ratio in the protoplanetary disc, which is likely imprinted into the host star metallicity, is a property that plays a crucial role during planet formation. On the observational side, statistical studies based on large exoplanet datasets have determined various correlations between planetary characteristics and host star metallicity. Aims. We aim to constrain planet formation and evolution processes by statistically analysing planetary systems produced at different metallicities by a theoretical model, and we compare them with the correlations derived from observational samples. Methods. We used the Generation III Bern model of planet formation and evolution to generate synthetic planetary systems at different metallicities. This global model incorporates the accretion of planetesimals and gas, planetary migration, N-body interactions between embryos, giant impacts, and protoplanetary disc evolution, as well as the planets' long-term contraction and atmospheric loss of gaseous envelopes. Using synthetic planets biased to observational completeness, we analysed the impact of stellar metallicity on planet occurrence rates, orbital periods, eccentricities, and the morphology of the radius valley. Results. Based on our nominal model, we find that (1) the occurrence rates of large giant planets and Neptune-sized planets are positively correlated with [Fe/H], while small sub-Earths exhibit an anti-correlation. In between, at radii of 1 to 3.5 R_⊕, the occurrence rate first increases and then decreases with increasing [Fe/H], with an inflection point at ~0.1 dex. (2) Planets with orbital periods shorter than ten days are more likely to be found around stars with a higher metallicity, and this tendency weakens with increasing planet radius. (3) Both giant planets and small planets exhibit a positive correlation between the eccentricity and [Fe/H], which could be explained by the self-excitation and perturbation of outer giant planets. (4) The radius valley deepens and becomes more prominent with increasing [Fe/H], accompanied by a lower super-Earth-to-sub-Neptune ratio. Furthermore, the average radius of the planets above the valley (2.1–6 R_⊕) increases with [Fe/H]. Conclusions. Our nominal model successfully reproduces many observed correlations with stellar metallicity either quantitatively or qualitatively, and supports the description of physical processes and parameters included in the Bern model. Quantitatively, the dependence of orbital eccentricity and period on [Fe/H] predicted by the synthetic population, however, is significantly weaker than observed. This discrepancy likely arises because the model only accounts for planetary interactions for the first 100 Myr and neglects the effects of the stellar environment (e.g. clusters, binaries). This suggests that long-term dynamical interactions between planets, along with the impact of binaries and/or companions, can drive the system towards a dynamically hotter state.

Context. Fast X-ray transients (FXTs) are a rare and poorly understood phenomenon with a variety of possible progenitors. The launch of the Einstein Probe (EP) mission has facilitated a rapid increase in the real-time discovery and follow-up of FXTs. Aims. We focus on the recent EP discovered transient EP241021a, which shows a peculiar panchromatic behavior, with the aim of understanding its origin. Methods. We obtained optical and near-infrared multiband imaging and spectroscopy with the Fraunhofer Telescope at Wendelstein Observatory, the Hobby-Eberly Telescope, and the Very Large Telescope of the newly discovered EP transient EP241021a over the first 100 days of its evolution. Results. EP241021a was discovered by EP as a soft X-ray trigger, but was not detected at gamma-ray frequencies. The observed soft X-ray prompt emission spectrum is consistent with nonthermal radiation, which requires at least a mildly relativistic outflow with a bulk Lorentz factor Γ ≳ 4. The optical and near-infrared light curve displays a two-component behavior, where an initially fading component, ∼ t^‑1, transitions to a rise steeper than ∼ t³ after a few days, before peaking at an absolute magnitude of M_r ≈ ‑21.8 mag and quickly returning to the initial decay. Standard supernova models are unable to reproduce either the absolute magnitude or the rapid timescale (< 2 d) of the rebrightening. The X-ray, optical and near-infrared spectral energy distributions display a red color, r ‑ J ≈ 0.8 mag, and point to a nonthermal origin (∼ ν^‑1) for the broadband emission. Considering a gamma-ray burst as a plausible scenario, we favor a refreshed shock as the cause of the rebrightening. This is consistent with the inference of an at least mildly relativistic outflow based on the prompt trigger. Conclusions. Our results suggest a link between EP-discovered FXTs and gamma-ray bursts, despite the lack of gamma-ray detections for the majority of EP transients.

Aims. We investigate the James Webb Space Telescope (JWST) MIRI MRS gas molecular content of an externally irradiated Herbig disk, the F-type XUE 10 source, in the context of the eXtreme UV Environments (XUE) program. XUE 10 belongs to the massive star cluster NGC 6357 (1.69 kpc), where it is exposed to an external far-ultraviolet (FUV) radiation ≈10³ times stronger than in the solar neighborhood. Methods. We modeled the molecular features in the mid-infrared spectrum with local thermodynamic equilibrium (LTE) 0D slab models. We derived basic parameters of the stellar host from a VLT FORS2 optical spectrum using PHOENIX stellar templates. Results. We detected bright CO₂ gas with the first simultaneous detection (>5σ) of four isotopologues (¹²CO₂, ¹³CO₂, ¹⁶O¹²C¹⁸O, ¹⁶O¹²C¹⁷O) in a protoplanetary disk. We also detected faint CO emission (2σ) and the HI Pf α line (8σ). We placed strict upper limits on the water content, finding a total column density of ≲10¹⁸ cm^‑2. The CO₂ species trace low gas temperatures (300–370 K) with a range of column densities of 7.4 × 10¹⁷ cm^‑2 (¹⁶O¹²C¹⁷O)‑1.3 × 10²⁰ cm^‑2 (¹²CO₂) in an equivalent emitting radius of 1.15 au. The emission of ¹³CO₂ is likely affected by line optical depth effects. The ¹⁶O¹²C¹⁸O and ¹⁶O¹²C¹⁷O abundances may be isotopically anomalous compared to the ¹⁶O/¹⁸O and ¹⁶O/¹⁷O ratios measured in the interstellar medium and the Solar System. Conclusions. We propose that the mid-infrared spectrum of XUE 10 is explained by H₂O removal either via advection or strong photo-dissociation by stellar UV irradiation and enhanced local CO₂ gas phase production. Outer disk truncation supports the observed CO₂‑H₂O dichotomy. A CO₂ vapor enrichment in ¹⁸O and ¹⁷O can be explained by means of external UV irradiation and early (10^4–5 yr) delivery of isotopically anomalous water ice to the inner disk.

Characterizing exoplanets' spectra is a crucial step in understanding the chemical and physical processes shaping their atmospheres and constraining their formation and evolutionary history. The X-SHYNE library is a homogeneous sample of 43 medium-resolution (R_λ ~ 8000) infrared (0.3–2.5 μm) spectra of young (<500 Myr), low-mass (<20 M_Jup), and cold (T_eff ~600–2000 K) isolated brown dwarfs and wide-separation companions observed with the VLT/X-Shooter instrument. To characterize our targets, we performed a global comparative analysis. We first applied a semiempirical approach. By refining their age and bolometric luminosity, we derived key atmospheric and physical properties, such as T_eff, mass, surface gravity (g), and radius, using the evolutionary model COND03. These results were then compared with the results from a synthetic analysis based on three self-consistent atmospheric models: the cloudy models Exo-REM and Sonora Diamondback, and the cloudless model ATMO. To compare our spectra with these grids we used the Bayesian inference code ForMoSA. We found similar L_bol estimates between both approaches, but an underestimated T_eff from the cloudy models, likely due to a lack of absorbers that could dominate the J and H bands of early L. We also observed a discrepancy in the log(g) estimates, which are dispersed between 3.5 and 5.5 dex for mid-L objects. We interpret this as a bias caused by a range of rotational velocities leading to cloud migration toward equatorial latitudes, combined with a variety of viewing angles that result in different observed atmospheric properties (cloud column densities, atmospheric pressures, etc.). This interpretation is supported by the correlation of the color anomaly Δ(J–K) of each object with log(g) and the parameter f_sed that drives the sedimentation of the clouds. Finally, while providing robust estimates of [M/H] and C/O for individual objects remains challenging, the X-SHYNE library globally suggests solar values that are consistent with a formation via stellar formation mechanisms. This study highlights the strength of homogeneous datasets in performing comparative analyses, reducing the impact of systematics, and ensuring robust conclusions while avoiding overinterpretation.

The goal of this work is to estimate the Hubble constant <inline-formula><tex-math>$H_0$</tex-math></inline-formula> through the time-delay cosmographic study of the quadruply lensed, variable quasi-stellar objects (QSO) SDSSJ1433+6007. We combine multifilter, archival Hubble Space Telescope data for lens modelling with a dedicated 3-yr long time-delay monitoring campaign using the 2.1 m Fraunhofer telescope at the Wendelstein Observatory. The lens modelling is performed with the public LENSTRONOMY PYTHON package individually for the infrared data, utilizing the higher resolution of the optical data to constrain image positions a priori. This approach revealed two luminous contaminants in one of the near-infrared exposures, which would bias the lensing potentials and cosmological inference if left unaccounted. After masking these contaminants, we repeated the modelling and combined the lens posteriors, obtaining a constraint on the Fermat potential with a statistical uncertainty of <inline-formula><tex-math>$2.6\, {{\rm per\ cent}}$</tex-math></inline-formula>. The g'-band Wendelstein light-curve data are reduced and then analysed using a free-knot spline fitting method implemented in the public PYTHON PYCS3 tools, accounting for microlensing correction. We obtain a precision of <inline-formula><tex-math>$6.5\, {{\rm per\ cent}}$</tex-math></inline-formula> for the time delays between the QSO images. By combining the posteriors for the Fermat potential differences and time delays, and assuming a flat Lambda-cold dark matter cosmology, we infer a Hubble constant of <inline-formula><tex-math>$H_0=71.7^{+3.9}_{-3.6}\, {\rm{km}}\,{\mathrm{Mpc}^{-1}~\mathrm{s}^{-1}}$</tex-math></inline-formula>, achieving <inline-formula><tex-math>$5.3\, {{\rm per\ cent}}$</tex-math></inline-formula> purely statistical uncertainty for this single system. Complementary observations and further study are required to address the systematic errors fully.

The obliquity between the stellar spin axis and the planetary orbit, detected via the Rossiter-McLaughlin (RM) effect, is a tracer of the formation history of planetary systems. While obliquity measurements have been extensively applied to hot Jupiters and short-period planets, they remain rare for cold and long-period planets due to observational challenges, particularly their long transit durations. We report the detection of the RM effect for the 19-hour transit of HIP 41378 f, a temperate giant planet on a 542-day orbit, observed through a worldwide spectroscopic campaign. We measured a slight projected obliquity of 21 ± 8° and a significant 3D spin-orbit angle of 52 ± 6°, based on the measurement of the stellar rotation period. HIP 41378 f is part a transiting system of five planets with planets close to mean motion resonances. The observed misalignment likely reflects a primordial tilt of the stellar spin axis relative to the protoplanetary disk, rather than dynamical interactions. HIP 41378 f is the first non-eccentric long-period planet (P>100 days) observed with the RM effect, opening new constraints on planetary formation theories. This observation should motivate the exploration of planetary obliquities across a longer range of orbital distances through international collaboration.

We investigate the influence of supernova (SN) feedback on the satellites of elliptical host galaxies using hydrodynamic simulations. Utilizing a modified version of the GADGET-3 code, we perform cosmological zoom-in simulations of 11 elliptical galaxies with stellar masses in the range 10¹¹M_⊙ < M_* < 2 × 10¹¹M_⊙. We conduct two sets of simulations with identical initial conditions: a fiducial model, which includes a three-phase SN mechanical wind, and a weak SN feedback model, where nearly all SN energy is released as thermal energy with a reduced SN wind velocity. Our comparison shows minimal differences in the elliptical host galaxies, but significant variations in the physical properties of satellite galaxies. The weak SN feedback model produces a larger number of satellite galaxies compared to the fiducial model, and significantly more than observed. For satellite galaxies with stellar masses above 10⁸M_⊙, the weak SN feedback model generates approximately 5 times more satellites than observed in the Extending the Satellites Around Galactic Analogs Survey (or xSAGA) survey. Most of these overproduced satellites have small stellar masses, below 10¹⁰M_⊙. Additionally, satellites in the weak SN feedback model are about 3.5 times more compact than those observed in the SAGA survey and the fiducial model, with metallicities nearly 1 dex higher than observed values. In conclusion, the satellite galaxies in the fiducial model, which includes mechanical SN feedback, exhibit properties that more closely align with observations. This underscores the necessity of incorporating both mechanical active galactic nuclei and SN feedback to reproduce the observed properties of elliptical galaxies and their satellites in simulations.

Context. Our knowledge of the initial conditions of terrestrial planet formation is mainly based on the study of protoplanetary disks around nearby isolated low-mass stars. However, most young stars and therefore planetary systems form in high-mass star-forming regions and are exposed to ultraviolet radiation, affecting the protoplanetary disk. These regions are located at large distances and only now with JWST has it become accessible to study the inner disks surrounding young stars. Aims. We present the eXtreme UV Environments (XUE) program, which provides the first detailed characterization of the physical and chemical properties of the inner disks around young intermediate-mass (1–4 M_⊙) stars exposed to external irradiation from nearby massive stars. We present high-signal-to-noise MIRI-MRS spectroscopy of 12 disks located in three subclusters of the high-mass star-forming region NGC 6357 (d ~ 1690 pc). Methods. Based on their mid-infrared spectral energy distribution, we classified the XUE sources into Group I and II based on the Meeus scheme. We analyzed their molecular emission features, and compared their spectral indices and 10 μm silicate emission profiles to the ones of nearby Herbig and intermediate T Tauri (IMTT) disks. Results. The XUE program provides the first detailed characterization of the rich molecular inventory in IMTT disks, including water, CO, CO₂, HCN, and C₂H₂. In the XUE sample, the detected emission likely originates from within 10 au, although this inner disk origin may not be typical for all externally irradiated disks. Despite being more massive, the XUE stars host disks with a molecular richness comparable to isolated T Tauri systems. The spectral indices are also consistent with similar-mass stars in nearby regions. The 10 μm silicate features in the XUE sample exhibit lower F_11.3/F_9.8 ratios at a given F_peak, suggesting that the disk surfaces may be dominated by smaller grains compared to nearby disks. However, uncertainties in extinction prevent us from drawing firm conclusions about their inner disk properties. The majority of disks display water emission from the inner disk, suggesting that even in these extreme environments rocky planets can form in the presence of water. Only one object shows PAH emission, contrasting with the higher PAH detection rates in IMTT surveys from lower-UV environments. Conclusions. The absence of strong line fluxes and other irradiation signatures suggests that the XUE disks have been truncated by external UV photons. However, this truncation does not appear to significantly impact the chemical richness of their inner regions. These findings indicate that even in extreme environments, IMTT disks can retain the ingredients necessary for rocky planet formation, comparable to the ones of lower-mass T Tauri disks in low-mass star-forming regions.

Context. Supergiant B[e] (sgB[e]) stars are exceptionally rare objects, with only a select number of confirmed examples in the Milky Way. The evolutionary pathways leading to the sgB[e] phase remain largely debated, highlighting the need for additional observations. The sgB[e] star Wd1-9, located in the massive cluster Westerlund 1 (Wd1), is enshrouded in a dusty cocoon – likely the result of past eruptive activity – leaving its true nature enigmatic. Aims. We present the most detailed X-ray study of Wd1-9 to date, using X-rays that pierce through its cocoon with the aim of uncovering its nature and evolutionary state. Methods. We utilised 36 Chandra observations of Wd1 from the 'Extended Westerlund 1 and 2 Open Clusters Survey' (EWOCS), plus eight archival datasets, totalling 1.1 Ms. We used this dataset to investigate long-term variability and periodicity in Wd1-9, and analysed X-ray colours and spectra over time to uncover patterns that shed light on its nature. Results. Wd1-9 exhibits significant long-term X-ray variability, within which we identify a strong ∼14-day periodic signal. We interpret this as the orbital period, marking the first period determination for the system. The X-ray spectrum of Wd1-9 is thermal and hard (kT ∼ 3.0 keV), resembling the spectra of bright Wolf-Rayet (WR) binaries in Wd1, while a strong Fe emission line at 6.7 keV indicates hot plasma from a colliding-wind X-ray binary. Conclusions. Wd1-9, with evidence of past mass loss, circumbinary material, a hard X-ray spectrum, and a newly detected 14-day period, displays all the hallmarks of a binary – likely a WR+OB – that recently underwent early Case B mass transfer. Its sgB[e] classification is likely phenomenological, reflecting emission from the dense circumbinary material. This places Wd1-9 in a rarely observed phase, possibly revealing a newly formed WN star, bridging the gap between immediate precursors and later evolutionary stages in Wd1.

Motivated by JWST observations of dense, clumpy, and clustered high-redshift star formation, we simulate the hierarchical assembly of nine <inline-formula><tex-math>$M_{\mathrm{cl}}={10^6}\:\mathrm{M_\odot }$</tex-math></inline-formula> star clusters using the BIFROST N-body code. Our low-metallicity models (<inline-formula><tex-math>$0.01Z_\odot$</tex-math></inline-formula>) with post-Newtonian equations of motion for black holes include evolving populations of single, binary, and triple stars. Massive stars grow by stellar collisions and collapse into intermediate-mass black holes (IMBHs) up to <inline-formula><tex-math>$M_\mathrm{\bullet }\sim {6200}\:\mathrm{M_\odot }$</tex-math></inline-formula>, stellar multiplicity boosting the IMBH masses by a factor of 2–3. The IMBHs tidally disrupt (TDE) <inline-formula><tex-math>$\sim 50$</tex-math></inline-formula> stars in 10 Myr with peak TDE rates up to <inline-formula><tex-math>$\Gamma \sim 5\times 10^{-5}$</tex-math></inline-formula> <inline-formula><tex-math>$\rm{yr}^{-1}$</tex-math></inline-formula> per cluster. These IMBHs are natural seeds for supermassive black holes (SMBHs) and the hierarchical assembly frequently leads to <inline-formula><tex-math>$&gt;2$</tex-math></inline-formula> SMBH seeds per cluster and their rapid mergers (<inline-formula><tex-math>$t&lt; 10$</tex-math></inline-formula> Myr). We propose that a gravitational wave (GW)-driven merger of IMBHs with <inline-formula><tex-math>${1000}\:\mathrm{M_\odot } \lesssim M_\bullet \lesssim {10\,000}\:\mathrm{M_\odot }$</tex-math></inline-formula> with comparable masses is a characteristic GW fingerprint of SMBH seed formation at redshifts <inline-formula><tex-math>$z&gt;10$</tex-math></inline-formula>, and IMBH formation in similar environments at lower redshifts. Massive star clusters provide a unique environment for the early Universe GW studies for the next-generation GW observatories including the Einstein Telescope and the Laser Interferometer Space Antenna.

A crucial ingredient affecting fast neutrino flavor conversion in core-collapse supernovae (SNe) is the shape of the angular distribution of the electron-neutrino lepton number (ELN). The presence of an ELN crossing signals favorable conditions for flavor conversion. However, the dependence of ELN crossings on the SN properties is only partially understood. We investigate a suite of 12 spherically symmetric neutrino-hydrodynamics simulations of the core collapse of a SN with a mass of <inline-formula><mml:math><mml:mrow><mml:mn>18.6</mml:mn><mml:msub><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mrow><mml:mo>⊙</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula>; each model employs different microphysics (i.e., three different nuclear equations of state, with and without muon creation) and includes or not a mixing-length treatment for proto-neutron star convection. We solve the Boltzmann equations to compute the neutrino angular distributions relying on static fluid properties extracted from each of the SN simulations in our suite for six selected postbounce times. We explore the dependence of the ELN distributions on the SN microphysics and proto-neutron star convection. We find that the latter shifts the proto-neutron star radius outward, favoring the appearance of ELN crossings at larger radii. On the other hand, muon creation causes proto-neutron star contraction, facilitating the occurrence of ELN crossings at smaller radii. These effects mildly depend on the nuclear equation of state. Our findings highlight the subtle impact of the SN microphysics, proto-neutron star convection, and neutrino transport on the ELN angular distributions.

In the standard formation models of terrestrial planets in the solar system and close-in super-Earths in non-resonant orbits recently discovered by exoplanet observations, planets are formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas in the final stage. This study aims to theoretically clarify a fundamental scaling law for the orbital architecture of planetary systems formed by giant impacts. In the giant impact stage, protoplanets gravitationally scatter and collide with one another to form planets. Using {\em N}-body simulations, we investigate the orbital architecture of planetary systems formed from protoplanet systems by giant impacts. As the orbital architecture parameters, we focus on the mean orbital separation between two adjacent planets and the mean orbital eccentricity of planets in a planetary system. We find that the orbital architecture is determined by the ratio of the two-body surface escape velocity of planets $v_\mathrm{esc}$ to the Keplerian circular velocity $v_\mathrm{K}$, $k$ = The mean orbital separation and eccentricity are about $2 ka$ and $0.3 k$, respectively, where $a$ is the system semimajor axis. With this scaling, the orbital architecture parameters of planetary systems are nearly independent of their total mass and semimajor axis.

We utilize the Magneticum suite of hydrodynamical simulations to investigate the formation and evolution of cosmic voids from $z = 5.04$ to present day, using cold dark matter and (sub-) halo tracers in high-density samples. This includes the evolution of their global properties, such as size, shape, inner density, and average density, as well as their radial density profiles. Our results provide several key conclusions for void analyses in modern surveys. We demonstrate that a relative size framework is required, mitigating methodological selection effects and revealing the true physical evolution of densities around halo-defined voids. This necessity arises from our findings that a void's properties are more fundamentally tied to its rank within its contemporary population than to its absolute size. Using this framework, we show that the evolution of halo voids stabilizes at redshifts below $z \simeq 1$, driven primarily by cosmic expansion rather than ongoing halo formation. We further find that the matter evolution around these stable voids is remarkably well-described by linear growth theory, with deviations appearing as non-linear growth on small scales and suppressed growth in the largest voids, potentially driven by the influence of dark energy. This late-time stability and the predictable evolution confirm voids as pristine laboratories for probing the nature of dark energy with upcoming surveys.