Sazuna/UAT_keywords huggingface dataset:
Boltzmann–Poisson Theory of Nonthermal Self-gravitating Gases, Cold Dark Matter, and Solar Atmosphere. Space and astrophysical plasmas or gases can reach various states of thermal or nonthermal quasi-equilibrium, depending on the collisional age of the observed system. Widely observed in space plasmas, the Kappa (or  —power-law) velocity distribution (KVD) is eloquent evidence of nonthermal states. M. P. Leubner has developed KVD models for luminous gases and cold dark matter (DM) with empirical density profiles described by   &gt; 0 and   &lt; 0, respectively. The predicted temperature profiles, however, are not in qualitative agreement with the nonmonotonic features expected in some gas and DM models. This study adopts the more consistent regularized Kappa distribution (RKD) to derive the equilibrium profiles of self-gravitating gas and DM halos within a Boltzmann–Poisson theoretical approach. The new RKD models can replicate better than the KVD models the Navarro–Frenk–White density profile of the DM near the basic halos and can also produce nonmonotonic temperature profiles. The same RKD formalism is also applied to non-self-gravitating astrophysical systems, which shows that for highly nonthermal cases (  &lt; 3/2), the temperature of the surrounding gases decreases initially in a narrow region. The temperature then increases sharply and reaches a high saturated value, resembling the overheated solar atmosphere, while the density profile near the surface may depart from the observations. Compared to the KVD models, the new RKD models can provide improved descriptions of gravitational equilibrium systems, especially for highly nonthermal cases and temperature profiles.

Keywords: Galaxy clusters, Solar atmosphere, Galaxy dark matter halos, Gravitational equilibrium, Gravitational fields, Cold dark matter, Navarro-Frenk-White profile, N-body problem
Tip of the Iceberg: Overmassive Black Holes at 4 &lt; z &lt; 7 Found by JWST Are Not Inconsistent with the Local <inline-formula> </inline-formula> Relation. JWST is revealing a remarkable new population of high-redshift (z ≳ 4), low-luminosity active galactic nuclei in deep surveys and detecting the host galaxy's stellar light in the most luminous and massive quasars at z ∼ 6 for the first time. Recent findings claim that supermassive black holes (SMBHs) in these systems are significantly more massive than predicted by the local black hole (BH) mass–stellar mass ( ) relation and that this is not due to sample selection effects. Through detailed statistical modeling, we demonstrate that the coupled effects of selection biases (i.e., finite detection limit and requirements for detecting broad lines) and measurement uncertainties can largely explain the reported offset and flattening in the observed   relation toward the upper envelope of the local relation, even for those at  . We further investigate the possible evolution of the   relation at z ≳ 4 with careful treatment of observational biases and consideration of the degeneracy between intrinsic evolution and dispersion in this relation. The bias-corrected intrinsic   relation in the low-mass regime ( ) suggests a large population of low-mass BHs ( ), possibly originating from lighter seeds, may remain undetected or unidentified. These results underscore the importance of forward modeling observational biases to better understand BH seeding and SMBH–galaxy coevolution mechanisms in the early universe, even with the deepest JWST surveys.

Keywords: Supermassive black holes, Early universe, Quasars, Active galaxies, Active galactic nuclei, Galaxy evolution
Dynamical and Atmospheric Characterization of the Substellar Companion HD 33632 Ab from Direct Imaging, Astrometry, and Radial-velocity Data. We present follow-up SCExAO/CHARIS H- and K-band (R ∼ 70) high-contrast integral field spectroscopy and Keck/NIRC2 photometry of directly imaged brown dwarf companion HD 33632 Ab and new radial-velocity data for the system from the SOPHIE spectrograph, complemented by Hipparcos and Gaia astrometry. These data enable more robust spectral characterization compared to lower-resolution spectra from the discovery paper and more than double the available astrometric and radial-velocity baseline. HD 33632 Ab's spectrum is well reproduced by a field L8.5–L9.5 dwarf. Using the Exo-REM atmosphere models, we derive a best-fit temperature, surface gravity, and radius of Teff = 1250 K, log(g) = 5, and R = 0.97 RJ, respectively, as well as a solar C/O ratio. Adding the SOPHIE radial-velocity data enables far tighter constraints on the companion's orbital properties (e.g., i =  o) and dynamical mass ( MJ) than derived from imaging data and Gaia eDR3 astrometry data alone. HD 33632 Ab should be a prime target for multiband imaging and spectroscopy with the James Webb Space Telescope and the Roman Space Telescope's Coronagraphic Instrument, shedding detailed light on HD 33632 Ab's clouds and chemistry and providing a key reference point for understanding young exoplanet atmospheres.

Keywords: Exoplanets, Brown dwarfs, Direct imaging, Adaptive optics
Tracing Coherent Gas Structures in the Central Region of the Starburst Galaxy NGC 253. II. Gas Excitation and Star Formation. Molecular gas in the central region of the starburst galaxy NGC 253 is complicated because of the combination of different gas kinematics, including stellar feedback, noncircular motions, and magnetic activity. In paper I, we used the latest multitransition, multi-isotope CO-line data sets obtained with the Atacama Large Millimeter/submillimeter Array to classify the molecular gas within the central 850 pc in radius into 28 coherent structures, and we proposed a three-dimensional geometric structure for the gas in the central region of this galaxy. In this paper, we utilize intensity ratios between 12CO (J = 3–2), 12CO (J = 1–0), HCN (J = 4–3), and SiO (J = 2–1) to investigate the physical properties of each coherent structure, comparing the distributions with (proto-)star clusters, known as superbubble candidates, and stars. We found that the excitation state of the gas tends to increase toward the galactic center, and we identified high-excitation states in the gas with noncircular motions. From analyses of HCN (J = 4–3) and SiO (J = 2–1), we found that the dense, star-forming clumps that drive the starburst reside either at the points connecting any two streams or in the central region where two oppositely directed, accretion flows terminate. Based on analyses of the intensity ratios and the proposed geometric structure, we suggest that some superbubbles may instead be the overlap of the coherent structures rather than an expanding shell. From all these results, we propose a scenario in which the starburst was triggered by cloud–cloud collisions caused by interactions of streams and/or by magnetic flotation and/or efficient accretion along a stellar bar.

Keywords: Starburst galaxies, Barred spiral galaxies, Interstellar line emission, Galaxy nuclei
Tidal Disruptions of Stars by Supermassive and Intermediate-mass Black Hole Binaries: The Effects of the First-order Post-Newtonian Cross Terms. In the vicinity of galactic nuclei, stars orbiting supermassive black hole (SMBH) binaries can undergo tidal disruption events (TDEs) due to the Lidov–Kozai mechanism and three-body interactions. While numerical simulations have incorporated post-Newtonian (PN) corrections up to 2.5PN order, they have not accounted for the 1PN cross-term effects among the three bodies. In this study, we employ N-body simulations to investigate the impact of the 1PN cross terms on the orbits of stars around an intermediate-mass black hole (IMBH) perturbed by an outer SMBH. Our findings indicate that while the 1PN cross terms do not substantially affect the fractions of stellar outcomes, they can cause considerable variations in the orbits of stars around IMBH–SMBH binaries. Specifically, we find that the inclusion of the 1PN cross terms can lead to more concentrated distributions of semimajor axes. Furthermore, we observe heavy tails in the distributions of temporal shifts in TDEs when these cross terms are included, with the maximum change reaching about 106 yr, approaching the maximum integration time of this study. This investigation underscores the critical importance of incorporating the 1PN cross terms to ensure accuracy in comprehensive simulations of multibody systems in galactic nuclei. Notably, for stars partially disrupted by an SMBH binary, omitting these cross terms could result in erroneous predictions.

Keywords: Stellar kinematics, Supermassive black holes, Tidal disruption, Galactic center
Reinvestigation of Fast Radio Burst Host Galaxy and Event Rate Density. Fast radio bursts (FRBs) are radio signals that last milliseconds. They originate from cosmological distances and have relatively high dispersion measures (DMs), making them excellent distance indicators. However, the origins of the FRB remain to be resolved. With its wide field of view and excellent sensitivity, CHIME/FRB has discovered more than half of all known FRBs. As more and more FRBs are located within or connected with their host galaxies, the study of FRB progenitors is becoming more important. In this work, we collect the currently available information related to the host galaxies of FRBs, and the Markov Chain Monte Carlo analysis about limited localized samples reveals no significant difference in the median of DMhost between repeaters and nonrepeaters. After examining and selecting CHIME/FRB samples, we estimate the local volumetric rate density of repeaters and nonrepeaters, accounting for different DMhost contributions, and compare with rates of predicted origin models and transient events. Our results indicate that DMhost significantly affects volumetric rates and offer insights into the origin mechanisms of FRB populations.

Keywords: Neutron stars, Magnetars, Radio bursts, Radio transient sources
Active Galactic Nucleus Feedback in Quiescent Galaxies at Cosmic Noon Traced by Ionized Gas Emission. We analyze ionized gas emission lines in deep rest-frame optical spectra of 14 massive (  M⊙) quiescent galaxies at redshifts 1.7 &lt; z &lt; 3.5 observed with JWST/NIRSpec by the Blue Jay survey. Robust detection of emission lines in 71% of the sample indicates the presence of ongoing ionizing sources in this passive population. The Hα line luminosities confirm that the population is quiescent, with star formation rates that are at least 10 times lower than the main sequence of star formation at z ∼ 2. The quiescent sample is clearly separate from the star-forming population in line diagnostic diagrams, and occupies a region usually populated by active galactic nuclei (AGN). Analysis of the observed line ratios, equivalent widths, and velocity dispersions leads us to conclude that in most cases the gas is ionized by AGN activity, despite the lack of X-ray detections. We measure generally low values of the bolometric luminosity Lbol ∼ 1044 erg s‑1 and Eddington ratio λ ∼ 10‑2–10‑3 for the central engines, typical of low-luminosity AGN. A subset of the sample also hosts ionized and neutral outflows, with ionized outflow velocities of the order of ∼1000 km s‑1. Our results show, for the first time using a representative sample, that low-luminosity AGN are extremely common among quiescent galaxies at high redshift. These low-luminosity AGN may play a key role in quenching star formation and in maintaining massive galaxies quiescent from Cosmic Noon to z ∼ 0.

Keywords: Quenched galaxies, Warm ionized medium, Active galactic nuclei, Galaxy evolution, Interstellar medium, Galaxy quenching, High-redshift galaxies, Early-type galaxies
Evolution of X-Ray Gas in SN 1987A from 2007 to 2021: Ring Fading and Ejecta Brightening Unveiled through Differential Emission Measure Analysis. As the nearest supernova (SN) observed since Kepler's SN of 1604, SN 1987A provides an unprecedented opportunity to study in detail the early evolution of supernova remnants. Despite extensive studies through both observations and simulations, there is still an urgent need for a more effective approach to integrate the results from two sides. In this study, we conducted a detailed differential emission measure (DEM) analysis on the XMM-Newton observations taken in 2007 to 2021 to characterize the continuous temperature structure of SN 1987A, which can be better compared with simulations. The X-ray plasma exhibits a temperature distribution with a major peak at ∼0.5–1 keV and a high-temperature tail extending to ≳5 keV. The emission measure (EM) of the major peak started to decline around 2014, while the EM of the tail continued increasing and appears to have formed a secondary peak at ∼3–5 keV in recent years. Our DEM results are consistent with simulations, which help to further identify the major peak as originating from the equatorial ring and the secondary peak as arising from the newly shocked ejecta. Together with the simulations, our DEM analysis reveals recent fading of the ring and brightening of the ejecta in X-rays from SN 1987A. Additionally, we observed a recent decrease in the centroid energy of the Fe K line, providing further evidence of newly shocked ejecta.

Keywords: X-ray astronomy, Supernova remnants, Interstellar medium
A Sea of Black Holes: Characterizing the LISA Signature for Stellar-origin Black Hole Binaries. Observations by the LIGO, Virgo, and KAGRA (LVK) detectors have provided new insights into the demographics of stellar-origin black hole binaries (sBHBs). A few years before gravitational-wave signals from sBHB mergers are recorded in the LVK detectors, their early coalescence will leave a unique signature in the ESA/NASA mission Laser Interferometer Space Antenna (LISA). Multiband observations of sBHB sources between the LISA and LVK detectors opens an unprecedented opportunity to investigate the astrophysical environment and multimessenger early alerts. In this study, we report the sBHB sources that are expected to be present in the LISA data derived directly from the hydrodynamic cosmological simulation Illustris. By surveying snapshots across cosmological volume, metallicity, and lookback time, we calculate the expected sBHBs present in the LISA data for various combinations of mission lifetimes and stellar population models. For stellar population estimates consistent with the LVK rates, we find that only 10 sBHBs across the Illustris snapshots would be detected with significant confidence for a 10 yr LISA mission, while a 4 yr LISA mission would detect only ∼1 sBHB. Our work paves the way for creating LISA mock data and benchmarking LISA detection pipelines directly using cosmological simulations.

Keywords: Gravitational wave astronomy, Stellar mass black holes, Gravitational waves
ngVLA Synthetic Observations of Ionized Gas in Massive Protostars. Massive-star formation involves significant ionization in the innermost regions near the central object, such as gravitationally trapped H II regions, jets, ionized disks, or winds. Resolved observations of the associated continuum and recombination line emission are crucial for guiding theory. The next-generation Very Large Array (ngVLA) will enable unprecedented observations of thermal emission with 1 mas resolution, providing a new perspective on massive-star formation at scales down to a few astronomical units at kiloparsec distances. This work presents synthetic interferometric ngVLA observations of the free–free continuum (93 GHz band), H41α, and H38α recombination lines from ionized jets and disks around massive protostars. Using the sf3dmodels Python package, we generate gas distributions based on analytical models, which are then processed through the RADMC-3D radiative transfer code. Our results indicate that the ngVLA can easily resolve, both spatially and spectrally, the ionized jet from a 15 M⊙ protostar at 700 pc, distinguishing between collimated jets and wide-angle winds, and resolving their launching radii, widths, and any substructure down to a few astronomical units. Detailed studies of radio jets launched by massive protostars will be feasible up to distances of ∼2 kpc. Furthermore, ngVLA will be able to study in detail the ionized disks around massive (&gt;10 M⊙) protostars up to distances from 4 to 12 kpc, resolving their kinematics and enabling the measurement of their central masses across the Galaxy. These observations can be conducted with on-source integrations of only a few hours.

Keywords: Radio astronomy, Compact H II region, Early stellar evolution, Radio jets, Star formation, Stellar accretion disks, Protostars, Radio interferometry, H II regions
Modeling the UV to Radio Spectral Energy Distribution of NGC 6946: Star Formation Rates and Dust Attenuation Properties. In this paper, we perform an ultraviolet (UV) to radio spectral energy distribution fitting analysis of star-forming regions in the nearby galaxy NGC 6946 by means of the Graphite and Silicates (GRASIL) population synthesis and radiative transfer model to which the first version of the thoroughly updated Padova and Trieste Stellar Evolutionary Code (PARSEC v1.2s) database of evolutionary nonrotating tracks of massive stars is incorporated. The tracks span a wide range of initial chemical compositions (Z = 0.0001–0.04) and stellar initial mass function (IMF) upper mass limits (Mup = 40 M⊙–350 M⊙). We obtain from our best-fit models consistent and robust estimates of star formation rate calibrations at wavelengths ranging from UV to radio and as a function of IMF upper mass limit. We investigate the properties of dust attenuation curves that also result from the best-fit models by exploiting the realistic treatment of dust performed by GRASIL. This resulted in new relations between optical emission fluxes that are subject to attenuation and fluxes that are not prone to attenuation. These relations, which we show to be almost independent of IMF upper mass limits, can be extremely useful in estimating attenuations in young high redshift galaxies.

Keywords: Star forming regions, Star formation, Spectral energy distribution, Spiral galaxies
The Protostars in Orion: Characterizing the Properties of Their Magnetized Envelopes. We present a study connecting the physical properties of protostellar envelopes to the morphology of the envelope-scale magnetic field. We used the Atacama Large Millimeter/submillimeter Array (ALMA) polarization observations of 61 young protostars at 0.87 mm on ~400–3000 au scales from the B-field Orion Protostellar Survey to infer the envelope-scale magnetic field, and we used the dust emission to measure the envelope properties on comparable scales. We find that protostars showing standard hourglass magnetic field morphology tend to have larger masses, and the nonthermal velocity dispersion is positively correlated with the bolometric luminosity and dust temperature of the envelope. Combining with the disk properties taken from the Orion VLA/ALMA Nascent Disk and Multiplicity survey, we connect envelope properties to fragmentation. Our results show a positive correlation between the fragmentation level and the angle dispersion of the magnetic field, suggesting that the envelope fragmentation tends to be suppressed by the magnetic field. We also find that protostars exhibiting standard hourglass magnetic field structure tend to have a smaller disk and smaller angle dispersion of the magnetic field than other field configurations, especially the rotated hourglass, but also the spiral and others, suggesting a more effective magnetic braking in the standard hourglass morphology of magnetic fields. Nevertheless, significant misalignment between the magnetic field and outflow axes tends to reduce magnetic braking, leading to the formation of larger disks.

Keywords: Circumstellar envelopes, Star forming regions, Interstellar magnetic fields, Star formation, Circumstellar disks, Magnetic fields
Sloan Digital Sky Survey IV MaStar: Quantification and Abatement of Interstellar Absorption in the Largest Empirical Stellar Spectral Library. We assess the impact of Ca II λ λ3934, 3969 and Na I λ λ5891, 5897 absorption arising in the interstellar medium (ISM) on the Sloan Digital Sky Survey-IV MaNGA Stellar Library (MaStar) and produce corrected spectroscopy for 80% of the 24,162-star catalog. We model the absorption strength of these transitions as a function of the stellar distance, Galactic latitude, and dust reddening based on high-spectral resolution studies. With this model, we identify 6342 MaStar stars that have negligible ISM absorption (W ISM(Ca II K) &lt; 0.07 Å and W ISM(Na I 5891) &lt; 0.05 Å). For 12,110 of the remaining stars, we replace their Na I D profile (and their Ca II profile for effective temperatures T eff &gt; 9000 K) with a coadded spectrum of low-ISM stars with similar T eff, surface gravity, and metallicity. For 738 additional stars with T eff &gt; 9000 K, we replace these spectral regions with a matching ATLAS9-based BOSZ model. This results in a mean reduction in W(Ca II K) (W(Na I D)) of 0.4–0.7 Å (0.6–1.1 Å) for hot stars (T eff &gt; 7610 K), and a mean reduction in W(Na I D) of 0.1–0.2 Å for cooler stars. We show that interstellar absorption in the simple stellar population (SSP) model spectra constructed from the original library artificially enhances W(Ca II K) by ≳20% at young ages (&lt;400 Myr); dramatically enhances the strength of stellar Na I D in starbursting systems (by ≳50%); and enhances stellar Na I D in older stellar populations (≳10 Gyr) by ≳10%. We provide SSP spectra constructed from the cleaned library and discuss the implications of these effects for stellar population synthesis analyses constraining the stellar age, [Na/Fe] abundance, and initial mass function.

Keywords: Interstellar line absorption, Galaxy stellar content, Astronomical techniques, Interstellar absorption, Spectroscopy