Sazuna/UAT_keywords huggingface dataset:
Fluctuation Dynamos in Supersonic Turbulence at Pm ≳ 1. Fluctuation dynamos provide a robust mechanism for amplifying weak seed magnetic fields in turbulent astrophysical plasmas. However, their behaviour in the highly compressible regimes characteristic of the interstellar medium remains incompletely understood. Using high-resolution 3D magnetohydrodynamic simulations of supersonic turbulence with rms Mach number  Mrms≍11 , we explore fluctuation dynamos across magnetic Prandtl numbers Pm = 1─10. At Pm = 1, dynamo growth is slower and saturates at lower magnetic-to-kinetic energy ratios, with amplification in the kinematic phase dominated by compression rather than line stretching. In contrast, at Pm = 10, vortical stretching emerges as the dominant mechanism, yielding faster growth, higher saturation levels, and stronger suppression of density─magnetic field correlations by magnetic pressure. This transition is reflected in the correlation coefficient between density and magnetic field strength, which is strongly positive at Pm = 1 but decreases significantly at higher Pm. Across all runs, the ratio of velocity-to-magnetic integral scales is ∼3.4, in the saturated phase, independent of Pm, while the ratio of viscous to resistive dissipation scales increases with the increase in Pm. Synthetic Faraday rotation measures reveal coherence lengths of ∼one-fourth to one-third of the forcing scale across the range of Pm explored. Using these coherence scales, we discuss the potential contribution of fluctuation dynamos to Faraday rotation expected from turbulent, gas-rich young disk galaxies.

Keywords: Interstellar magnetic fields, Magnetohydrodynamics, Magnetohydrodynamical simulations
Cosmology with Supernova Encore in the Strong Lensing Cluster MACS J0138─2155: Time Delays and Hubble Constant Measurement. Multiply imaged supernovae (SNe) provide a novel means of constraining the Hubble constant (H0). 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 H0 thus far. Here we detail the third such measurement for SN Encore, a z = 1.95 Type Ia SN 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 H0 constraint. Our final time-delay measurement is  ∆t1b,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  H0=66.9−8.1+11.2kms−1Mpc−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 H0.

Keywords: Cosmology, Type Ia supernovae, Gravitational lensing, Hubble constant
SNR 1987A: Spitzer Data from Days 6000 to 8000 Revisited. An excess emission has been observed by Spitzer in the 3─5 μm range of the SNR 1987A spectrum. It is generally argued that this excess could be due to the presence of warm amorphous carbon dust in the equatorial ring around the supernova, but the proposed models all have problems. This prompted us to present an alternative view on the interpretation of the spectral energy distribution (SED) of SNR 1987A from the near-IR wavelengths to the radio frequencies (from 3 μm up to 1.4 GHz), between 6000 and 8000 days after outburst. We argue that the origin of that excess could be attributed instead to a free─free emission. We show that under very specific conditions (the free─free is self-absorbed at a cutoff frequency imposed by the mass of the emitting region), it could be produced by collisional heating of the gas. We then discuss the time evolution of the various components of the SED. We establish a linear relationship between the growth of the warm carbon dust mass and that of the silicates dust during the analyzed period. Finally, we build the Spitzer light curves, and we show that our models reproduce the observations pretty well, although our study clearly favors the free─free case. In conclusion, we argue that the free─free model provides a formally very good description of the data; however, the model does require some very specific parameter choices, and results in an unusually low temperature for the ionized gas.

Keywords: Type II supernovae, Broad band photometry, Infrared Astronomical Satellite
A Fast, Parallelized, GPU-accelerated Photochemical Model, XODIAC, with Built-in Equilibrium Chemistry and Multiple Chemical Networks for Exoplanetary Atmospheres. The launch of the James Webb Space Telescope has delivered high-quality atmospheric observations and expanded the known chemical inventory of exoplanetary atmospheres, opening new avenues for atmospheric chemistry modeling to interpret these data. Here, we present XODIAC, a fast, GPU-accelerated, one-dimensional photochemical model with a built-in equilibrium chemistry solver, an updated thermochemical database, and three chemical reaction networks. This framework enables comparative atmospheric chemistry studies, including the newly developed XODIAC-2025 network, a state-of-the-art C-H-O-N-P-S-Metals network, linking 594 species through 7720 reactions. The other two are the existing publicly available C-H-O-N-S and C-H-O-N-S-Metals networks, from the established photochemical models VULCAN and ARGO, respectively, which are commonly used in the community. The XODIAC model has been rigorously benchmarked on the well-studied hot Jupiter HD 189733 b, with results compared against these two models. Benchmarking shows excellent agreement and demonstrates that when the same chemical network and initial conditions are used, the numerical scheme for solving atmospheric chemistry does not significantly affect the results. We also revisited the atmospheric chemistry of HD 189733 b and performed a comparative analysis across the three networks. Sulfur chemistry shows the least variation across networks, carbon chemistry shows slightly more, and phosphorus chemistry varies the most, primarily due to the introduction of unique PHO and PN pathways comprising 390 reactions in the XODIAC-2025 network. These findings highlight XODIAC's capability to advance exoplanetary atmospheric chemistry and provide a robust framework for comparative exoplanetology.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres, Exoplanets, Exoplanet atmospheric structure
The Lyα and Continuum Origins Survey. III. Investigating the Link between Galaxy Morphology, Merger Properties, and LyC Escape. Characterizing the mechanisms and galaxy properties conducive to the escape of ionizing (LyC) emission is necessary to accurately model the Epoch of Reionization and identify the sources that powered it. Using Hubble Space Telescope data, the Lyα and Continuum Origins Survey (LaCOS) is the first program to obtain uniform, multiwavelength subkiloparsec imaging for a large sample (42) of galaxies observed in LyC and enable statistically robust studies between LyC and resolved galaxy properties. Here, we characterize the morphology and galaxy merger properties of LaCOS galaxies and investigate their connection with the escape fraction of LyC emission  fescLyC . We find strong anticorrelations between  fescLyC  and size (r20, r50, and r80) measured in filters containing emission from star-forming regions, and with the asymmetry and clumpiness in F150LP, a filter tracing UV continuum and Lyα. We find that ≥48% of LaCOS galaxies, and ≥41% of LaCOS LyC-emitters are visually classified as galaxy mergers. Galaxies robustly identified as mergers in LaCOS are at advanced stages of interaction, close to coalescence. The  fescLyC  properties of robust mergers and low-probability mergers cannot be differentiated statistically, and we only find significant difference between the two populations in terms of their sizes and LyC luminosity: robust mergers having larger values. We conclude that (i)  fescLyC  tends to be larger in galaxies with a small number of compact, centrally located, UV-emitting star-forming regions, (ii) mergers at advanced stages of interaction represent a sizable fraction of LyC-emitting samples at z ∼ 0.3, and (iii) mergers can facilitate the escape of LyC photons from galaxies.

Keywords: Hubble Space Telescope, Ultraviolet astronomy, Galaxy mergers, Lyman-alpha galaxies, Reionization, Galaxies
Detectability of Atmospheric Biosignatures in Earth Analogs with Varying Surface Boundary Conditions: Prospects for Characterization in the UV, Visible, Near-infrared, and Mid-infrared Regions. The search for potentially habitable exoplanets centers on detecting biosignature molecules in Earth-like atmospheres, making it crucial to understand their detectability under biologically and geologically influenced conditions. In this study, we model the reflection and thermal emission spectra of such atmospheres in the UV/VIS/near-IR and mid-IR regions and simulate their detectability using future mission concepts such as the Habitable Worlds Observatory (HWO) and the Large Interferometer for Exoplanets (LIFE). We employ numerical weather prediction model data, based on Earth's atmosphere, to derive temperature─pressure profiles and integrate a 1D photochemical model to assess the detectability of these molecules in Earth analogs located 10 pc away. We investigate the dominant reaction pathways and their contributions to the atmospheric composition of an Earth analog, with a focus on how they shape the resulting molecular signatures. We also examine the role of surface boundary conditions, which indirectly trace the effects of biological and geological processes, on the detectability of these molecules using HWO- and LIFE-type mission concepts. Our findings indicate that O3 is detectable with both mission concepts, while H2O requires specific surface humidity levels for detection with LIFE and shows only potential detectability with HWO. CO2 is detectable with LIFE. Both N2O and CH4 require continuous outgassing for potential detection with LIFE, and CH4 further requires low surface humidity to prevent masking by water features. Our work highlights the feasibility of characterizing the atmospheres of Earth analogs in the UV/VIS/near-IR and mid-IR domains using HWO- and LIFE-type mission concepts and provides valuable insights for the development of future missions operating in these spectral regions.

Keywords: Exoplanet atmospheres, Exoplanets
Tails of Gravity: Persistence of Star Formation in the Central Molecular Zone. We characterize star-forming gas in six molecular clouds (Sgr B1-off, Sgr B2, Sgr C, the 20 and 50 km s−1 molecular clouds, and the Brick) in the Galactic central molecular zone (CMZ), and compare their star-forming activities with those in molecular clouds outside the CMZ. Using multiband continuum observations taken from Planck, Herschel, James Clerk Maxwell Telescope/SCUBA-2, and Caltech Submillimeter Observatory/SHARC2, we derived 8 .″ 5 resolution column density maps for the CMZ clouds and evaluated the column density probability distribution functions (N-PDFs). With the archival Atacama Large Millimeter/submillimeter Array 1.3 mm dust continuum data, we further evaluated the mass of the most massive cores ( Mcoremax ). We find that the N-PDFs of four of the selected CMZ clouds are well described by a piecewise log-normal+power-law function, while the N-PDFs of the remaining two can be approximated by log-normal functions. In the first four targets, the masses in the power-law component ( Mgasbound ),  Mcoremax , and star formation rate are correlated. These correlations are very similar to those derived from low-mass clouds in the solar neighborhood and massive star-forming regions on the Galactic disk. These findings lead to our key hypotheses: (1) in the extreme environment of the CMZ, the power-law component in the N-PDF also represents self-gravitationally bound gas structures, and (2) evolution and star-forming activities of self-gravitationally bound gas structures may be self regulated, insensitive to the exterior environment on ≳5─10 pc scales.

Keywords: Galactic center, Star formation, Initial mass function, Molecular clouds
Axisymmetric Modeling of DSHARP Dusty Disks: Asymmetric Structures and Inner-disk Dispersal. High-resolution observations of Class II protoplanetary disks frequently reveal annular structures that may indicate the presence of embedded planets. In this study, we model brightness profiles and geometries for 16 dusty disks in the DSHARP observations to identify asymmetric substructures, including possible planet-induced signatures. We find no compelling evidence for circumplanetary emission in these systems. We identify a possible one-armed spiral in Elias 27; while previous studies report an m = 2 spiral, the morphology of the newly identified spiral agrees with a spiral for a possible protoplanet. Although nondetection of circumplanetary emission is consistent with low expected luminosities, the absence of additional dust spirals except for Elias 27 may constrain properties of potential embedded planets given their theoretical detectability. The analyses further suggest that spiral amplitudes and phases correlated with gap and ring locations in WaOph 6 and IM Lup, appearing as deflections of spirals in images. Five disks exhibit strong residual asymmetries attributable to the vertical extent of their dust layers. We find that the brightness temperature of inner disks (1─5 au) declines with stellar age on a ∼3 Myr timescale, while the total flux shows no clear decreasing trend. This trend is consistent with the presence of pressure bumps that retain large dust grains at outer radii, while allowing the inner disks to disperse. The universality of the disk dispersal timescale at millimeter wavelengths, observed in both the extended DSHARP disks and the compact disks from previous demographic surveys, may constrain timing of planet formation, including habitable planets.

Keywords: Radio interferometry, Protoplanetary disks
Diffusive or Ballistic? Distributions and Spectra of PeV Cosmic Rays around Microquasars. In the standard Galactic cosmic-ray (CR) paradigm, protons are accelerated up to ∼1 PeV by Galactic sources. While supernova remnants have been traditionally considered as the primary accelerators, recent observations by LHAASO and HAWC have detected very-high-energy (VHE) gamma rays exceeding 100 TeV from several microquasars, suggesting that these X-ray binaries can accelerate CRs beyond 1 PeV. We investigate the escape process of CRs from microquasars, focusing on the energy-dependent transport mechanisms. High-energy CRs are likely to have long mean free paths and move ballistically on scales smaller than their mean free path, while lower-energy CRs undergo diffusive propagation. This transition results in a spectral break in the CR distribution around the microquasar. We calculate CR energy spectra within a 10─30 pc radius for various diffusion coefficients and timescales. Our model predicts a spectral break and hardening at Ep ∼ 10─100 TeV when the standard diffusion coefficient for the interstellar space is assumed. However, current VHE gamma-ray observations do not show clear spectral breaks, suggesting that the diffusion coefficient may be significantly reduced near microquasars, possibly due to magnetic field amplification by CR-driven turbulence.

Keywords: Interstellar medium, X-ray binary stars, High energy astrophysics, Cosmic rays
Broadband Variability Analysis of the Flat-spectrum Radio Quasar PKS 0402−362 with Indications of Quasi-periodic Modulation. We present a comprehensive temporal and spectral study of the flat-spectrum radio quasar (FSRQ) PKS 0402−362 using Fermi Large Area Telescope/Swift X-Ray Telescope/UVOT observations spanning from MJD 54686 to 60321. The γ-ray light curve exhibits multiple phases of enhanced activity, with the fractional variability parameter (Fvar) showing larger amplitudes at longer timescales, consistent with variability trends observed in other FSRQs. Statistical analysis of the flux and spectral index distributions using the Anderson─Darling test and histogram fitting reveals that both distributions deviate from a single log-normal form and are better represented by a double log-normal profile, indicating two distinct flux states. A search for quasi-periodic oscillations in the γ-ray emission using the Lomb─Scargle periodogram identified a significant periodic signal at ∼413 days with a confidence level exceeding 3σ. However, the proximity of the timescale to one year and the limited number of observed cycles prevents a definitive interpretation. Broadband spectral energy distributions for six flux states were modeled using a one-zone leptonic framework incorporating synchrotron, synchrotron self-Compton, and external Compton components. The spectral energy distributions are well reproduced with physically reasonable parameters: high-flux states exhibit harder electron spectra and lower magnetic field strengths (B ∼ 0.2─0.6 G), while low-flux states show softer spectra and stronger magnetic fields (B ∼ 1.3 G). The fitted break energy decreases during high-flux states, suggesting enhanced radiative cooling and a transition toward a particle- or kinetic-energy─dominated jet. These trends are consistent with the "harder-when-brighter" behavior commonly observed in blazars.

Keywords: Blazars, Active galaxies, Non-thermal radiation sources, Relativistic jets
Synchrotron Self-Compton Radiation in the ICMART Model: Spectral Simulations and Application to the Record-breaking GRB 221009A. This paper presents simulations of the synchrotron self-Compton (SSC) spectrum within the Internal-Collision-induced Magnetic Reconnection and Turbulence (ICMART) model. We investigate how key parameters like the magnetization σ0 shape the broadband spectral energy distribution by regulating the electron distribution and magnetic field strength. The overall spectrum typically comprises two components: synchrotron radiation peaking at Ep with a low-energy spectral index α between −1 and −1.5 and an SSC component peaking at Essc. At high energies, Klein─Nishina (KN) suppression causes an exponential cutoff. The flux ratio Y between these components is critical: when Y is small, the SSC peak can be suppressed. Spectral features of the synchrotron component reveal the underlying physical conditions: harder spectra with α ∼ −1 indicate a large Y parameter and strong KN suppression. We find a positive correlation between Y and σ0, contrasting with internal shock model predictions. Applied to GRB 221009A, our model suggests σ0 ≤ 20 can reproduce the MeV─TeV observations. This study underscores the value of combined MeV─TeV observations in probing gamma-ray burst emission mechanisms.

Keywords: Gamma-ray bursts, High energy astrophysics
Difference between Half-mass Radius and Half-light Radius of Galaxies at 0.2 &lt; z &lt; 2.5 Revealed by JWST/NIRCam Data. Using JWST observations in CANDELS fields, we measure the half-light radius (re,light) and half-mass─radius (re,mass) for 14,333 galaxies with stellar masses M* &gt; 109M⊙ at redshifts 0.2 &lt; z &lt; 2.5. To investigate the difference between re,light and re,mass, we find that re,light is larger than re,mass for both quiescent galaxies (QGs) and star-forming galaxies (SFGs). Moreover, the difference between these two radii is clearly correlated with galaxy stellar mass, re,light, and the rest-frame U − V color. When examining the evolution of the re,mass/re,light ratio, we observe a significant increase for SFGs at z &gt; 1.7. In contrast, no clear increase is observed for QGs at z &gt; 1, though a slight decreasing trend is seen between 0.2 &lt; z &lt; 1.0. By fitting a linear relationship between galaxy size and stellar mass, we find that the slope for re,light is ∼0.1─0.3 dex larger than that for re,mass. In terms of galaxy size evolution at a fixed stellar mass, the re,mass of QGs increases by a factor of ∼3─5 from z ∼ 2.5 to z ∼ 0.2. In contrast, the re,mass of SFGs increases by a factor of approximately 2 over the same redshift range, with this growth trend closely following that of their re,light. These results indicate that previous insights into galaxy evolution based on re,light remain valid when considering re,mass, although the specific slopes show some variations.

Keywords: Galaxy formation, Galaxy evolution, Galaxy radii
New Hard X-Ray and Multiwavelength Study of the PeVatron Candidate Pulsar Wind Nebula G0.9+0.1 in the Galactic Center Region. We present a new X-ray study and multiwavelength spectral energy distribution (SED) modeling of the young pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1747─2809, inside the composite supernova remnant (SNR) G0.9+0.1, located in the Galactic center region. The source is detected by NuSTAR up to 30 keV with evidence for the synchrotron burnoff effect in the changing spatial morphology with increasing energy. The broadband 2─30 keV spectrum of PWN G0.9+0.1 is modeled by a single power law with photon index Γ = 2.11 ± 0.07. We combined the new X-ray data with multiwavelength observations in radio, GeV, and TeV gamma rays and modeled the SED, applying one-zone and multizone leptonic models. The comparison of the models is successful, as we obtained physically compatible results in the two cases. Through the one-zone model, we constrain the age of the system to ∼2.2 kyr, as well as reproduce the observed PWN and SNR radio sizes. In both the one-zone and multizone leptonic models, the electron injection spectrum is well described by a single power law with spectral index p ∼ 2.6 and a maximum electron energy of ∼2 PeV, suggesting the source could be a leptonic PeVatron candidate. We estimate the average magnetic field to be BPWN ∼ 20 μG. We also report the serendipitous NuSTAR detection of renewed X-ray activity from the very faint X-ray transient XMMU J174716.1─281048 and characterize its spectrum.

Keywords: High energy astrophysics, Gamma-ray sources, Spectral energy distribution, X-ray sources, Pulsar wind nebulae