Sazuna/UAT_keywords huggingface dataset:
Time Evolution of Optical Darkness in Gamma-Ray Burst Afterglow: The Case of GRB 240825A. Long-duration gamma-ray bursts (GRBs) are believed to occur in star-forming regions. The multiwavelength follow-up observations of the early afterglow of GRB 240825A provided insights into the evolution of the optical-to-X-ray spectral feature of the afterglow. We comprehensively investigate the evolution of X-ray spectral properties through time-resolved spectral analysis and calculate optical darkness (βOX) to reveal the physical properties of the afterglow. The X-ray-to-optical spectral energy distributions of afterglow in different time intervals are fitted to derive the extinction curves. The βOX exhibits a trend of decreasing and then increasing, reaching its minimum value at ∼1000 s post-trigger. However, at 11 hr post-trigger, βOX does not meet the criteria for an optically dark burst. The extinction curves in different time intervals indicate that GRB 240825A occurred in a dust-obscured environment.

Keywords: Interstellar dust, Gamma-ray bursts, Interstellar dust extinction, Interstellar medium
Galaxy Protoclusters as Drivers of Cosmic Reionization: I. Bubble Overlap at Redshift z ∼ 7 in LAGER-z7OD1. Since the launch of JWST, the sample size of reionization-era Lyα emitters (LAEs) has been steadily growing; yet inferences about the neutral hydrogen fraction in the intergalactic medium exhibit increasing variance at redshift z ≍ 7, possibly indicating significant field-to-field fluctuations in the progression of cosmic reionization. In this paper, we present new JWST/NIRSpec and Keck/LRIS spectra of nine LAEs in the redshift z ∼ 7 protocluster LAGER-z7OD1. Measurements of Lyα transmission and Lyα velocity offset along multiple sight lines map the Lyα damping wing optical depth across the galaxy overdensity. In the standard context of inside-out ionization, we estimate the radii of ionized bubbles,  Rimin=0.07− 0.69 Mpc (physical), based on the distance from each LAE to the first neutral patch along the sight line. The resulting 3D topology reveals three distinct subclusters where the ionized bubbles are approaching overlap. Five of the nine LAEs plausibly ionized their bubbles, where a few bursts of star formation and a modest escape fraction are sufficient. We demonstrate, however, that the actual ionized volumes are likely larger, at least  Riism  = 0.42─1.29 Mpc (physical), based on an empirical model for interstellar attenuation of Lyα. Modeling galactic attenuation of Lyα significantly increases the inferred intergalactic transmission (thus enlarging the ionized path length). The error bars on the reddening correction allow fully overlapping bubbles, and our results are consistent with accelerated reionization in the protocluster.

Keywords: AGN host galaxies, Starburst galaxies, Galaxy clusters, High-redshift galaxy clusters, Interacting galaxies, Galaxy evolution, Reionization, High-redshift galaxies
The Distribution of Quenched Galaxies in the Massive z = 0.87 Galaxy Cluster El Gordo. El Gordo (ACT-CL J0102−4915) is a massive galaxy cluster with two major mass components at redshift z = 0.87. Using spectral energy distribution fitting results from JWST/NIRCam photometry, the fraction of quenched galaxies in this cluster was measured in two bins of stellar mass:  9&lt;log(M*/M⊙)&lt;10  and  10≤log(M*/M⊙)&lt;12 . While there is no correlation between the quenched fraction and angular separation from the cluster's overall center of mass, there is a correlation between the quenched fraction and angular separation from the center of the nearest of the two mass components for the less-massive galaxies. This suggests that environmental quenching processes are in place at z ∼ 1, and that dwarf galaxies are more affected by those processes than massive galaxies.

Keywords: Galaxy clusters, Star formation, Galaxy evolution, Galaxy quenching, Galaxies
Microlensing Signatures of Dyson Sphere─like Structures around Primordial Black Holes as Technosignatures of Extraterrestrial Advanced Civilizations. We investigate the microlensing detectability of extraterrestrial technosignatures originating from Dyson sphere-like structures, such as Dyson swarms surrounding primordial black holes. These hypothetical swarms consist of stochastically varying, partially opaque structures that could modulate standard microlensing light curves through time-dependent transmission effects. We introduce a probabilistic framework that includes a stochastic transmission model governed by variable optical depth and random gap distributions. We perform a parameter scan and generate heat maps of the optical transit duration. We study the infrared excess radiation and peak emission wavelength as complementary observational signatures. Additionally, we define and analyze the effective optical depth and the anomalous microlensing event rate for these stochastic structures. Our findings provide a new avenue for searching for extraterrestrial advanced civilizations by extending microlensing studies to include artificial, dynamic modulation signatures.

Keywords: Search for extraterrestrial intelligence, Astrobiology, Primordial black holes
AGN Feedback Models and AGN Demographics. I. Radio-mode AGN in EAGLE, SIMBA, and TNG100 Are Inconsistent with Observations. We compare predictions of how active galactic nuclei (AGNs) populate host galaxies at low redshifts to observations, finding large discrepancies between cosmological simulation predictions and observed patterns. Modern cosmological simulations include AGN feedback models tuned to reproduce the observed galaxy stellar mass function. However, due to a lack of real understanding of the physics of AGN feedback, these models vary significantly across simulations. To distinguish between the models and potentially test the underlying physics, we carry out independent tests of these models. In an earlier study, we found that FAGN—the observed completeness-corrected fraction of galaxies hosting radio AGNs with an Eddington ratio λ &gt; 10−3—to be a strong function of host-galaxy stellar mass (M⋆) but nearly independent of host specific star formation rates (sSFRs) at fixed M⋆. In this study, we test the radio mode AGN feedback models of the EAGLE, SIMBA, and TNG100 simulations by comparing their predictions of  FAGNM⋆  to our observational constraint. We find that none of these simulations even qualitatively reproduce the observed dependencies of FAGN on M⋆ and sSFR. Finally, we find that although the given TNG100 model could be modified in order to better reproduce the observed FAGN trend, this modification would likely also change its prediction for the local stellar mass function and star formation rates—key observations used for calibrating the simulation in the first place. Our findings highlight a pressing need to revisit the AGN feedback prescriptions in EAGLE, SIMBA, TNG100, and other similar models.

Keywords: AGN host galaxies, Galaxy formation
Constraining the Nature of Dark Matter from Tidal Radii of Cluster Galaxy Subhalos. Gravitational lensing by galaxy clusters provides a powerful probe of the spatial distribution of dark matter and its microphysical properties. Strong and weak lensing constraints on the density profiles of subhalos and their truncation radii offer key diagnostics for distinguishing between collisionless cold dark matter (CDM) and self-interacting dark matter (SIDM). Notably, in the strongly collisional SIDM regime, subhalo core collapse and enhanced mass loss from ram-pressure stripping predict steeper central density slopes and more compact truncation radii—features that are directly testable with current lensing data. We analyze subhalo truncation in eight lensing clusters (A2218, 383, 963, 209, 2390, and MACS J0416.1, J1206.2, J1149.6) that span the redshift range  zspec≃0.17 ─0.54 with virial masses M200 ≃ 0.41─2.2 × 1015 M⊙ to constrain SIDM versus CDM. Our results indicate that the outer spatial extents of subhalos are statistically consistent with CDM, corroborated by redshift- and mass-matched analogs from the IllustrisTNG simulations. We conclude that the tidal radii of cluster galaxy subhalos serve as an important and complementary diagnostic of the nature of dark matter in these violent, dense environments.

Keywords: Galaxy clusters, Galaxy dark matter halos, Tidal radius, Gravitational lensing, Dark matter
Dynamics of Null-points across Shocks Interacting with Preexisting Turbulence. In this study, we utilize 2.5D resistive magnetohydrodynamic (MHD) simulations to examine the generation and evolution of plasmoids resulting from the interaction between shock waves and turbulence in interplanetary space. We focus on (quasi-)perpendicular shock geometries with an out-of-plane mean magnetic field to investigate the impact of preexisting large-scale turbulent magnetic fluctuations upstream on MHD shock waves and on magnetic reconnection in the downstream region. Our findings reveal several key insights. First, the magnetic turbulence spectra exhibit three ranges: a low-k range characterized by cascading, a mid-k range potentially mediated by reconnection, and a high-k range corresponding to resistive diffusion. Importantly, these spectral features, including their characteristic breaks and slopes, remain invariant across the shock transition. Second, in all cases, the downstream occurrence of X-points and O-points increases, saturates to a peak value for a certain interval, and gradually decreases away from the shock. This behavior of X-points is consistent with the in situ measurements taken by the Magnetospheric Multiscale mission at Earth's bow shocks. Third, the resistive simulations allow for the explicit calculation of the magnetic reconnection rate per unit area in the x─y plane, indicating a higher rate per unit area downstream than upstream. This is consistent with the increased occurrence of X-points.

Keywords: Interplanetary shocks, Solar magnetic reconnection, Interplanetary turbulence, Solar wind, Plasma astrophysics
Probing the Peak of Star Formation with the Stochastic Background of Binary Black Hole Mergers. Although the LIGO─Virgo─KAGRA collaboration detects many individually resolvable gravitational-wave events from binary black hole mergers, those that are too weak to be identified individually contribute to the stochastic gravitational-wave background. Unlike the standard cross-correlation search for excess correlated power, a Bayesian search method that models the background as a superposition of an unknown number of mergers enables simultaneous inference of the properties of high-redshift binary black hole populations and accelerated detection of the background. In this work, we apply this templated background search method to 1 day of simulated data at the current LIGO Hanford─Livingston detector network sensitivity to determine whether the weakest mergers contribute information to the detection of the background and to the constraint on the merger redshift distribution at high redshifts. We find that the dominant source of information for the detection of the stochastic background comes from mergers with signal-to-noise ratios just below the individual detection threshold. However, we demonstrate that the weakest mergers do contribute to the constraint on the shape of the redshift distribution not only beyond the peak of star formation, but also beyond the redshifts accessible with individually detectable sources.

Keywords: Gravitational wave astronomy, Gravitational wave sources, Astrophysical black holes
Tracing Early Cosmic Chemical Enrichment: A Uniform XMM-Newton Survey of Metallicity in Galaxy Groups and Clusters. Observed metal abundances in the intracluster medium (ICM) of galaxy groups and clusters, ZICM, exceed what is expected from present-day stellar populations alone. Galaxy clusters are presumed to be near closed-box systems, allowing constraints to be placed on the origins of metals and stellar populations responsible for ZICM. We present a uniform XMM-Newton survey of 26 galaxy groups and clusters, measuring radial metallicity profiles and relating ZICM with the stellar fraction M*/Mgas. We determine ZICM via spectral fitting across multiple annuli, finding a best fit of  ZICM=−0.08−0.07+0.07logM*Mgas+0.30−0.06+0.06  with intrinsic scatter  σp=0.09−0.01+0.02 . We use closed-box chemical evolution models to estimate the metallicity yield from observable stellar populations, incorporating updated supernova yields and corrections for metals locked in remnants,  Z*=(1.14±0.52)log1+M*Mgas . Our results demonstrate that present-day stellar populations systematically underpredict ZICM, with an inferred excess component increasing in systems with low M*/Mgas. This trend supports the need for an early enrichment population (EEP) distinct from visible stars, ZEEP. We find this necessity holds when reconsidering the closed-box assumption by removing all galaxy groups, potential leaky systems, deriving ZEEP within 1σ when including and excluding groups. Three systems (NGC 1132, NGC 5098, and NGC 4325) deviate from the survey trend, exhibiting steep negative radial metallicity gradients and unusually low ZICM. We posit these systems to be late forming, whose ICM enrichment reflects only recent stellar populations. Our analysis quantifies the necessity of an EEP and provides trends for testing cluster chemical evolution models.

Keywords: Galaxy clusters, Intracluster medium, Metallicity, X-ray astronomy
Helium Depletion in Escaping Atmospheres of Sub-Neptunes: A Signature of Primary-to-secondary Transition. Short-period sub-Neptunes are common in extrasolar systems. These sub-Neptunes are generally thought to have primary atmospheres of protoplanetary-disk gas origin. However, atmospheric escape followed by degassing from their interiors can lead to the transition to secondary atmospheres depleted in gases less soluble in magma, such as helium. These primary and secondary atmospheres can potentially be distinguished from observations of escaping hydrogen and helium. This study aims to elucidate the impact of the primary-secondary transition on the atmospheric compositions of short-period sub-Neptunes. We simulate their evolution with atmospheric escape driven by stellar X-ray and extreme ultraviolet irradiation and degassing of hydrogen, helium, and water from their rocky interiors, with a 1D structure model. We show that the transition takes place for low-mass, close-in planets that experience extensive atmospheric escape. These planets show the depletion of helium and enrichment of water in their atmospheres because of their low and high abundances in the planetary interiors, respectively. A compilation of our parameter survey (the orbital period, planetary mass, envelope mass, and mantle FeO content) shows a correlation between the planet radius and the helium escape rate. We suggest that the transition from primary to secondary atmospheres may serve as an explanation for helium non-detection for relatively small (≲2.5 R⊕) exoplanets.

Keywords: Exoplanet atmospheric composition , Exoplanets, Hot Neptunes, Super Earths, Exoplanet evolution, Mini Neptunes, Exoplanet formation, Exoplanet atmospheric evolution, Exoplanet atmospheres, Exoplanet atmospheric structure
Unveiling the Sources of X-Ray Luminosity in DESI Galaxy Groups: Insights from the SRG/eROSITA All-sky Survey. We use the first eROSITA all-sky survey to investigate the contributions of active galactic nuclei (AGN) and extended gas to the total X-ray luminosity (LX) of galaxy groups with different halo masses (Mh) at different redshifts. The presence of AGN in their central galaxies is identified using multiwavelength catalogs, including the X-ray counterparts, the ASKAP radio catalog, and the DESI spectroscopic measurements. We apply the stacking method to obtain sufficient statistics for the X-ray surface brightness profile and the LX for groups with different central AGN properties. We find that the X-ray groups exhibit the highest LX, followed by groups with QSO, radio, Baldwin─Phillips─Terlevich AGN, and non-AGN centrals. Moreover, the LX of the Mh ≲ 1013h−1M⊙ groups is dominated by the central AGN, while the X-ray emission from extended gas tends to be more prominent in the Mh ≳ 1013h−1M⊙ groups. In groups where the AGN play a major role in X-ray emission, the contribution from extended gas is minor, resulting in significant uncertainties concerning the extended X-ray emission. When the subset containing the X-ray-detected counterparts is excluded, the extended gas component becomes easier to obtain. A correlation has been identified between the X-ray luminosity of the central AGN and extended gas. However, once we account for the positional offset, their correlation becomes less prominent. Currently, the results are not conclusive enough to confirm whether there is a connection between the AGN feedback and extended gas. However, they provide a new perspective on the feedback processes in the history of group assembly.

Keywords: Intracluster medium, Galaxy groups, Circumgalactic medium
Multiwavelength Afterglows as Diagnostic Probes of Dense Circumburst Medium in GRBs. Gamma-ray bursts (GRBs) are generally believed to occur in environments where the surrounding medium is either a uniform interstellar medium, or in some cases, a dense stellar wind from a massive progenitor. Recently, GRB 191019A has been proposed to originate within the accretion disk of an active galactic nucleus (AGN), suggesting that some GRBs may occur in extremely dense environments, although this interpretation remains under debate. This scenario has drawn considerable attention, as AGN disks are promising sites that can host progenitors of both long and short GRBs, and their dense, gas-rich environment could significantly influence jet propagation and afterglow emission. Yet our theoretical understanding of the resulting afterglow signatures in such environments is limited, and further systematic exploration is required. In this study, we investigate how multiwavelength afterglow light curves can be utilized as diagnostic tools to probe the nature of the circumburst environment. Our results show that, in dense environments, GRB afterglows exhibit distinct frequency-dependent behaviors. For jets with large opening angles, the X-ray light curve displays a shallow decay or bump due to a transition from synchrotron to synchrotron self-Compton (SSC) dominance, while the optical and high-energy (GeV) light curves follow typical power-law decays. On the other hand, for small opening angles, the light curves exhibit wavelength-dependent jet breaks: the GeV and optical bands break simultaneously, while the X-ray break is delayed as the SSC component gradually compensates for the fading synchrotron component. These signatures provide potential diagnostics of GRBs occurring in dense media such as AGN disks.

Keywords: Gamma-ray bursts, Active galactic nuclei, Relativistic jets
Black Hole Polarimetry. II. The Connection between Spin and Polarization. We study synchrotron polarization in spatially resolved horizon-scale images, such as those produced by the Event Horizon Telescope (EHT). In both general relativistic magnetohydrodynamic (GRMHD) simulations and simplified models of the black hole magnetosphere, the polarization angle, quantified by the complex observable ∠β2, depends strongly and systematically on the black hole spin. This relationship arises from the coupling between spin and the structure of the magnetic field in the emission region, and it can be computed analytically in the force-free limit. To explore this connection further, we develop a semianalytic inflow framework that solves the time-stationary axisymmetric equations of GRMHD in the black hole's equatorial plane; this model can interpolate between the force-free and inertial regimes by varying the magnetization of the inflow. Our model demonstrates how finite inertia modifies the structure of the electromagnetic field and can be used to quantitatively predict the observed polarization pattern. By comparing reduced models, GRMHD simulations, and analytic limits, we show that the observed synchrotron polarization can serve as a robust diagnostic of spin under assumptions about Faraday rotation and the emission geometry. Applied to EHT data, the model disfavors high-spin configurations for both M87∗ and Sgr A∗, highlighting the potential of polarimetric imaging as a probe of both black hole spin and near-horizon plasma physics.

Keywords: Magnetohydrodynamics, Polarimetry, Black holes
A Deep Chandra View of A2597: Bubbles, Shocks, Cold Fueling, and a Plasma Depletion Layer. To examine how active galactic nucleus (AGN) feedback shapes the intracluster medium (ICM) and fuels black hole accretion in the cool-core galaxy cluster A2597, we present deep (∼600 ks) Chandra X-ray observations complemented by archival GMRT radio and SINFONI near-infrared data. Radio-mode AGN activity has inflated seven X-ray cavities and driven one to three potential weak shocks ( M∼1.05−1.14 ) extending to ∼150 kpc, suggesting recurrent outbursts occurring on ∼107 yr timescales. We also detect a narrow, ∼57 kpc X-ray surface brightness deficit—a potential plasma depletion layer—likely shaped by residual sloshing motions that amplified magnetic fields and/or displaced gas within the cluster core. Although the AGN injects ∼1044 erg s−1 of energy, comparable to the cluster's cooling luminosity, radiative cooling persists at ∼15 M⊙ yr−1, replenishing the billion-solar-mass cold gas reservoir at the heart of the brightest cluster galaxy. Sustaining this level of activity requires a continuous fuel supply, yet the estimated Bondi accretion power (∼2 × 1043 erg s−1) falls an order of magnitude short of the observed cavity power, suggesting that "hot" gas fueling is insufficient. Instead, archival Atacama Large Millimeter/submillimeter Array observations continue to support a chaotic cold accretion scenario, where turbulence-driven condensation fuels the AGN at rates exceeding Bondi accretion, sustaining a self-regulated feedback cycle that repeatedly shapes the core of A2597.

Keywords: Galaxy clusters, Shocks, Active galactic nuclei
The Complete Sample of Available SNe Ia Luminosity Calibrations from the TRGB Observed with either HST or JWST. Distance ladders, which calibrate the luminosity of Type Ia supernovae (SNe Ia), currently provide the strongest constraints on the local value of H0. Recent studies from the Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) show good consistency between measurements of SNe Ia host distances. These are calibrated to NGC 4258 using different primary distance indicators (Cepheids, Tip of the Red Giant Branch or TRGB), J-region Asymptotic Giant Branch, and Miras). However, some subsamples of calibrated SNe Ia employed to measure H0 yield noteworthy differences due to small sample statistics, but also due to differences in sample selection. This issue is particularly important for TRGB-derived calibrations owing to the smaller volume they reach compared to Cepheids, reducing sample size and enhancing the size of statistical fluctuations. To mitigate this issue, we compile the largest and complete (as currently available) sample of HST or JWST measurements of the TRGB in the hosts of normal SNe Ia for a total of N = 35, 50% larger than the previous largest. Most are present in the literature, and we compile multiple measures when available. We also add 5 SNe Ia hosts from the HST archive, not previously published. The full sample together with the Pantheon+ SN catalog gives H0 = 72.1─73.3 ± 1.8 km s−1 Mpc−1 (depending on methodology), in good agreement with the value of 72.5 ± 1.5 km s−1 Mpc−1 from HST Cepheids in hosts of 42 SNe Ia calibrated by the same anchor, NGC 4258. We trace the difference in the result of H0 = 70.4 ± 1.9 km s−1 Mpc−1 from W. L. Freedman et al. to 11 hosts not selected for that CCHP compilation (of N = 24), which alone yield H0 = 74.1 km s−1 Mpc−1, 2σ higher than the selected sample. A smaller increase of 0.6 km s−1 Mpc−1 comes from a commonly employed correction for peculiar velocities.

Keywords: Cosmology, Red giant tip, Cosmological parameters, Hubble Space Telescope, HST photometry, Distance indicators, Hubble constant, James Webb Space Telescope, Type Ia supernovae, Galaxies