Sazuna/UAT_keywords huggingface dataset:
Optical Emission from Luminous and Very Soft X-Ray Sources in Nearby Galaxies: Testing the Scenario of Edge-on Supercritical Accretion Systems. Supercritical accretion onto compact objects is expected to drive optically thick winds, resulting in observed X-ray emission as a function of viewing angle. However, their optical emission, either from the outer accretion disk or companion surface, tends to be nearly isotropic. Based on a sample of luminous and very soft X-ray sources that are argued to be supercritical accretion systems viewed close to edge-on, we identify the optical counterparts for some of them and compare the optical properties with those of ultraluminous X-ray sources, which are supposed to be supercritical accretion systems viewed close to face-on. The optical luminosity is found in a wide range, with the absolute visual magnitude ranging from dimmer than −1.2 in some sources to about −7 in one case. Most sources show a power-law-like spectrum, while four of them display a blackbody shape. One of them shows an optical spectrum resembling a B-type main sequence, suggesting that it may be a Be white dwarf system. Strong variability in flux at timescales as short as 10 days are revealed, indicating that some of these sources are powered by accretion onto compact objects. These suggest that the luminous and very soft X-ray sources in nearby galaxies have a diverse population, and some of them are indeed consistent with emission from supercritical accretion, with consistent optical magnitudes and colors. Future optical spectroscopic observations are needed to further constrain their natures.

Keywords: Be stars, Ultraluminous x-ray sources, X-ray sources, Stellar accretion
Spectral Energy Correlations of Gamma-Ray Bursts from Structured Jets. Using 148 out-axis gamma-ray bursts (GRBs), we build their spectrum–energy relations of peak energy versus isotropic energy, peak energy versus peak luminosity, and peak energy versus jet-calibrated energy, which are corrected for a structured jet model. These relations are found to depend on the observer's viewing angle as long as the observer is within the jet cone. After converting the out-axis energy relations to the in-axis situations, we find that the corresponding in-axis energy relations are universally steeper, of which all of them can be roughly interpreted by the synchrotron radiation mechanism as shown in Xu et al. Meanwhile, we notice that the in-axis means of isotropic energies are about 1 order of magnitude larger than the out-axis means for both short and long bursts except the supernova-associated GRBs. Furthermore, we apply all the newly found energy relations to construct the Hubble diagrams of out/in-axis bursts. It is found that the in-axis Hubble diagrams are better cosmological indicators.

Keywords: Gamma-ray bursts
The Role of Population III Star Tidal Disruption Events in Black Hole Growth at the Cosmic Dawn. The discovery of supermassive black holes (SMBHs) at high redshifts has intensified efforts to understand their early formation and rapid growth during the cosmic dawn. Using a semi-analytical cosmological framework, we investigate the role of tidal disruption events (TDEs) involving Population III (Pop III) stars in driving the growth of heavy-seed black holes (104−106 M⊙). Our results indicate that Pop III TDEs significantly accelerate the growth of relatively lighter massive black holes (∼104−105 M⊙), allowing them to increase their mass by roughly an order of magnitude within the first 10 Myr. Cosmological evolution modeling further supports such Pop-III-TDE-driven growth scenarios being consistent with the formation pathways of observed luminous high-redshift quasars originating from seed black holes at 10 &lt; z &lt; 15. We also discuss future observational probes of these early-stage growth processes that future facilities, including space-based gravitational-wave observatories and infrared telescopes like JWST, could potentially conduct. These findings provide a clear observational framework to test the critical role of Pop III star interactions in the rapid buildup of SMBHs during the earliest epochs.

Keywords: Tidal disruption, Population III stars, Astrophysical black holes
Surrogate Modeling of Landau Damping with Deep Operator Networks. Kinetic simulations excel at capturing microscale plasma physics phenomena with high accuracy, but their computational demands make them impractical for modeling large-scale space and astrophysical systems. In this context, we build a surrogate model, using Deep Operator Networks (DeepONets), based upon the Vlasov–Poisson simulation data to model the dynamical evolution of plasmas, focusing on the Landau damping process—a fundamental kinetic phenomenon in space and astrophysical plasmas. The trained DeepONets are able to capture the evolution of electric field energy in both linear and nonlinear regimes under various conditions. Extensive validation highlights DeepONets' robust performance in reproducing complex plasma behaviors with high accuracy, paving the way for large-scale modeling of space and astrophysical plasmas.

Keywords: Space plasmas, Plasma astrophysics, Plasma physics
StreamGen: Connecting Populations of Streams and Shells to Their Host Galaxies. In this work, we study how the abundance and dynamics of populations of disrupting satellite galaxies change systematically as a function of host galaxy properties. We apply a theoretical model of the phase-mixing process to classify intact satellite galaxies and stellar streamlike and shell-like debris in ∼1500 Milky Way–mass systems generated by a semi-analytic galaxy formation code, SatGen. In particular, we test the effect of host galaxy halo mass, disk mass, ratio of disk scale height to length, and stellar feedback model on disrupting satellite populations. We find that the counts of tidal debris are consistent across all host galaxy models, within a given host mass range, and that all models can have streamlike debris on low-energy orbits, consistent with that observed around the Milky Way. However, we find a preference for streamlike debris on lower-energy orbits in models with a thicker (lower-density) host disk or on higher-energy orbits in models with a more massive host disk. Importantly, we observe significant halo-to-halo variance across all models. These results highlight the importance of simulating and observing large samples of Milky Way–mass galaxies and accounting for variations in host properties when using disrupting satellites in studies of near-field cosmology.

Keywords: Galaxy formation, Theoretical models, Stellar streams, Tidal disruption, Galaxy structure, Galaxy disks, Dark matter
Formation of Complex Organic Molecules in Prestellar Cores: The Role of Nondiffusive Grain Chemistry. We present the results of astrochemical modeling of complex organic molecules (COMs) in the ice and gas of the prestellar core L1544 with the recently updated MONACO rate equation-based model. The model includes, in particular, nondiffusive processes, new laboratory verified chemical routes for acetaldehyde and methane ice formation, and variations of H and H2 desorption energies depending on the surface coverage by H2 molecules. For the first time, we simultaneously reproduce the abundances of several oxygen-bearing COMs in the gas-phase, the approximate location of the peak of methanol emission, as well as the abundance of methanol in the icy mantles of L1544. Radical–radical reactions on the grain surface between species such as CH3, CH3O, and HCO efficiently proceed nondiffusively. COMs are delivered to the gas-phase via chemical desorption amplified by the loops of H-addition/abstraction surface reactions. However, gas-phase chemical reactions as well provide a noticeable input to the formation of COMs in the gas, but not to the COMs solid-state abundances. This particularly applies for CH3CHO and CH3OCH3. The simulated abundances of COMs in the ice are in the range 1%–2% (for methyl formate ice) or ∼0.1% (for CH3CHO and CH3OCH3) with respect to the abundance of H2O ice. We stress a similarity between the simulated abundances of icy COMs in L1544 and the abundances of COMs in the gas-phase of hot cores/corinos. We compare our nondiffusive model with the diffusive model and provide constraints for the species' diffusion-to-desorption energy ratios.

Keywords: Interstellar abundances, Astrochemistry, Star formation, Interstellar dust processes, Chemical reaction network models, Complex organic molecules
Pavo: Stellar Feedback in Action in a Low-mass Dwarf Galaxy. MeerKAT observations of the recently discovered, extremely low mass galaxy Pavo have revealed a neutral gas (H I) reservoir that was undetected in archival H I single dish data. We measure Pavo's H I mass as  logMHI/M⊙=5.79±0.05 , making it the lowest mass H I reservoir currently known in an isolated galaxy (with a robust distance measurement). Despite Pavo's extreme isolation, with no known neighbor within over 700 kpc, its H I reservoir is highly disturbed. It does not show clear signs of rotation, and its center of mass is offset from the stellar body center by 320 pc, while its peak is offset by 82 pc (both in projection). Despite this disturbed morphology, Pavo still appears to be consistent with the H I size–mass relation, although it is not possible to accurately determine a suitable inclination correction. Such disturbed, offset, and disorganized H I reservoirs are predicted by simulations of low-mass, star-forming dwarfs in which supernova-driven outflows efficiently disrupt the interstellar medium after a star formation (SF) event. It is likely that we are witnessing Pavo in precisely this period, tens to a few hundred Myr after a SF episode, when internal feedback has disrupted its gas reservoir.

Keywords: Dwarf irregular galaxies, Galaxy evolution, Interstellar atomic gas, Low surface brightness galaxies
Probing Turbulence, Gravity, Supernovae, and Magnetic Field Effects with the 6D Kinematics of Young Stars in Milky Way Star-forming Regions. The dynamics of star-forming gas can be affected by many physical processes, such as turbulence, gravity, supernova explosions, and magnetic fields. In this paper, we investigate several nearby star-forming regions (Orion, Upper Sco, Taurus, and Perseus) for kinematic imprints of these influences on the newly formed stars. Using Gaia DR3 astrometry and APOGEE DR17 radial velocities, we compute first-order velocity structure functions (VSFs) of young stars in galactic Cartesian coordinates in both 6D (3D positions and 3D velocities) and 4D (3D positions and each 1D velocity) to identify signatures of turbulence and anisotropic motion. We also construct 3D and 1D radial velocity profiles to identify coherent expansion trends, and compare stellar proper motions to plane-of-sky magnetic field orientations in Taurus and Perseus. We find that the VSFs are mildly anisotropic, with slightly different amplitudes, slopes, or features in different directions in several groups, but in general, they are all consistent with Larson's Relation at intermediate length scales, especially in less compact groups. In several cases, the VSFs exhibit features suggestive of local energy injection from supernovae. Radial velocity profiles reveal clear anisotropic expansion in multiple groups, with the most extreme cases corresponding to those with the most anisotropic VSFs. In Perseus, we find that the motions of young stars are preferentially perpendicular to the local magnetic field. We find multiple, overlapping causes in each group for the observed kinematics. Our findings support that young stars remember more than just the turbulent state of their natal clouds.

Keywords: Stellar kinematics, Star forming regions, Interstellar medium
Quenching through Tidal Gas Removal: Molecular Gas and Star Formation in Tidal Tails of z ∼ 0.7 Post-starburst Galaxies. The active suppression of star formation in galaxies is critical for preventing the growth of overly massive systems and explaining the formation of present-day elliptical galaxies. We present a high-resolution, spatially resolved, multiwavelength study of two z ∼ 0.7 massive post-starburst galaxies, SDSS J1448+1010 and SDSS J2258+2313, from the Studying Quenching in Intermediate-z Galaxies: Gas, angu L→ ar momentum, and Evolution (SQuIGG L→ E) survey, providing new insights into the role of mergers in driving quenching. Atacama Large Millimeter/submillimeter Array CO(2─1) observations show that both galaxies removed ∼50% of their molecular gas into extended tidal tails, spanning up to 65 kpc, following recent mergers. Hubble Space Telescope Wide Field Camera 3 imaging and grism spectroscopy show that while SDSS J1448+1010 exhibits Hα emission in its northern tidal tail consistent with ongoing star formation, SDSS J2258+2313 lacks detectable star-forming activity outside the central galaxy. Very Large Array 6 GHz continuum data reveal compact radio emission in SDSS J2258+2313, while SDSS J1448+1010 hosts small radio jets indicative of active galactic nucleus activity. Both galaxies retain substantial molecular gas reservoirs in their central regions, which appear more turbulent than "normal" star-forming galaxies, likely contributing to the observed low star formation rates in the hosts. Despite the similarities in their cold gas content and tidal features, the galaxies are distinct from each other in their star formation, gas─star alignment, and radio morphology, highlighting the complexity of tidal gas removal as a quenching mechanism at intermediate redshifts.

Keywords: Molecular gas, Tidal tails, Star formation, Galaxy mergers, Galaxy quenching, Post-starburst galaxies
SN 2023vbg: A Type IIn Supernova Resembling SN 2009ip, with a Long-duration Precursor and Early-time Bump. Type IIn supernovae (SNe) resembling SN 2009ip (09ip-like SNe) originate from the interaction between circumstellar material (CSM) and the ejecta. This subclass not only shares similar observational properties around the maximum but is also commonly characterized by a long-duration precursor before its maximum. Investigating the observed properties of the precursor provides constraints on the mass-loss history of the progenitor. We present observational data of SN 2023vbg, an 09ip-like type IIn SN that displayed unique observational properties compared to other 09ip-like SNe. SN 2023vbg showed a long-duration precursor at Mg ∼ ‑14 mag lasting for ∼100 days, followed by a bright bump at Mg ∼ ‑17 mag at 12–25 days before the maximum. The luminosity of the precursor is similar to those of other 09ip-like SNe, but the bright bump has not been observed in other cases. After reaching the peak luminosity, the light curve exhibited a relative smooth decline. While the Hα profile displays two velocity components (∼500 and 3000 km s‑1), a broad component observed in other 09ip-like SNe was not seen, but it may emerge later. We suggest that these properties are explained by the difference in the CSM structure as compared to other 09ip-like SNe; SN 2023vbg had an inner denser CSM component, as well as generally smooth CSM density distribution in a more extended scale than in the others. Such diversity of CSM likely reflects the diversity of pre-SN outbursts, which in turn may mirror the range of evolutionary pathways in the final stages of the progenitors.

Keywords: Supernovae
Oxyster: A Circumgalactic Low-ionization Oxygen Nebula next to a Starburst Galaxy at z ∼ 1. Extended emission line nebulae around galaxies or active galactic nuclei (AGNs) provide a unique window to investigate the galactic ecosystem through the circumgalactic medium (CGM). Using Subaru Hyper Suprime-Cam narrowband imaging and spectroscopic follow-up, we serendipitously discover "Oxyster"—a large ionized nebula next to an interacting starburst galaxy at z = 0.924. The nebula is traced by extended [O II] λλ3726, 3729 (∼30 kpc) and [O III] λ5007 (∼20 kpc) emission lines. On the nebula luminosity─size plane, Oxyster surpasses the extended narrow-line regions around low-z AGNs, resembling a higher-z analog of "Hanny's Voorwerp." However, its uniformly low [O III]/[O II] ratio (O32) sets it apart from typical AGN light echoes. For the host galaxy, Hubble Space Telescope and JWST images reveal a disturbed red disk galaxy with a single blue spiral "arm." Spectral energy distribution fitting suggests the (2─6) × 1010 M⊙ host galaxy sits above the star-forming main sequence with an ongoing starburst, especially in the "arm," and has &lt;5% luminosity contribution from AGNs, consistent with X-ray nondetection and the radio continuum. Standard photoionization and shock models struggle to explain simultaneously Oxyster's emission line luminosities, low O32 ratio, and the nondetection of the Hβ line. A plausible explanation could involve the combination of a recent (&lt;108 yr) starburst and a low-luminosity AGN (Lbol ∼ 1 × 1042 erg s−1). While Oxyster's nature awaits future investigation, its discovery highlights the potential of ground-based narrowband imaging to uncover extended emission line nebulae around non-AGN systems, opening new avenues for studying the CGM of normal galaxies in the early Universe.

Keywords: AGN host galaxies, Starburst galaxies, Galaxy formation, Galaxy evolution, Circumgalactic medium
Influence of Density Distribution on Synchrotron Polarization Dispersion in Magnetized Interstellar Medium. Faraday rotation measure (RM) synthesis is a well-known approach originated in B. J. Burn and later developed by M. A. Brentjens &amp; A. G. de Bruyn for studying magnetic fields. This work presents a complementary approach—the polarization frequency analysis (PFA)—allowing for the properties of the turbulent magnetic field, which are difficult to include in B. J. Burn's original approach. Based on synthetic polarization observation of magnetohydrodynamic turbulence simulation data, we study the influence of the coupling effect between density and magnetic field on synchrotron polarization dispersion. By applying the PFA to different simulated interstellar turbulence environments, we find that the PFA technique can reveal the scaling slope of the turbulent magnetic field in the case of a weak coupling effect and can also reflect the scaling slope of the RM in the case of a strong coupling effect. Since it avoids the influence of Faraday depolarization, the PFA technique is a promising way to uncover turbulence properties using observational data from the Low-Frequency Array for Radio Astronomy and the Square Kilometre Array.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Astrostatistics techniques, Interstellar synchrotron emission
On the Origin of a Possible Hard Very High Energy Spectrum from M87 Discovered by LHAASO. Recent LHAASO observations hint at potential spectral hardening around 20 TeV in M87's very high energy emission, suggesting a possible new radiation component. In this work, we construct averaged multiwavelength spectral energy distributions by combining data from Chandra and Swift-UVOT/XRT covering the same period as the LHAASO detection to investigate the origin of this feature. We test several radiation mechanisms, including the pp interaction, proton synchrotron emission, photomeson process, and two-zone leptonic model. We find that only the pion decay gamma rays in pp interactions can interpret this feature in the framework of the one-zone model. With analytical analysis, we prove that proton synchrotron emission cannot generate a hard spectrum above 0.17 TeV. The photomeson model requires an emission zone compressed near the Schwarzschild radius of the central supermassive black hole, incompatible with broadband optical-GeV spectral constraints. In addition, the two-zone leptonic model also emerges as a viable alternative.

Keywords: Gamma-ray sources, Active galactic nuclei
A Comparative Study of Halo Mass Estimates from Group Catalogs and Lensing Signals. We compare halo mass estimates from three galaxy group catalogs (redMaPPer, Yang21, and Zou21) with those derived from gravitational lensing measurements. Each catalog employs distinct methodologies, including mass–richness relations, abundance matching, and luminosity-based calibration. A linear correlation is observed between catalog-estimated and lensing-derived masses. The redMaPPer catalog shows the best agreement, especially for lower-redshift groups, with minor deviations in higher-redshift bins. Yang21 is the only catalog containing low mass groups, which gives a reasonably good mass estimation, except for the lowest mass bin. Cross-matched groups between redMaPPer and Yang21 reveal the former catalog provides more accurate mass estimation, while the Yang21 makes underestimation of halo mass for those sharing the central galaxy with redMaPPer and overestimation of halo mass for those with different center determination with redMaPPer and for the unique Yang21 groups. These findings emphasize the importance of redshift-dependent calibration and refined group definitions for accurate mass estimation.

Keywords: Weak gravitational lensing, Galaxy dark matter halos, Galaxy clusters
Rapid Binary Mass Transfer: Circumbinary Outflows and Angular Momentum Losses. High rates of stable mass transfer likely occur for some binary star systems, but the resulting flow of mass and angular momentum (AM) is unclear. We perform hydrodynamical simulations of a polytropic donor star and a point-mass secondary to determine the mass, AM, and velocity of gas that leaves the system, and the dependence on binary parameters such as mass ratio. The simulations use an adiabatic equation of state and do not include radiative cooling or irradiation of the outflow. Mass transfer is initiated by injecting heat into the stellar envelope, causing it to gradually inflate and overflow its Roche lobe. The transferred mass flows into an accretion disk, but soon begins to escape through the outer Lagrange point (L2), with a lesser amount escaping through the L3 point. This creates an equatorially concentrated circumbinary outflow with an opening angle of 10°–30° with a wind-like density profile ρ ∝ r‑2. We find that the ratios of the specific AM of the outflowing gas over that of the L2 point are approximately {0.95, 0.9, 0.8, 0.65} for mass ratios q = {0.25, 0.5, 1, 2} (accretor/donor). The asymptotic radial velocity of the outflowing gas, in units of the binary orbital velocity, is approximately 0.1–0.2 for the same mass ratios, except for q = 0.25, where it might be higher. This outflow, if ultimately unbound from the binary, may be a source of circumstellar material that interacts with ejecta from a subsequent supernova or stellar merger.

Keywords: Close binary stars, Hydrodynamical simulations, Interacting binary stars, Semi-detached binary stars