Sazuna/UAT_keywords huggingface dataset:
Diversity of Cold Worlds: A Near-complete Spectral Energy Distribution for 2MASS J04151954‑0935066 Using JWST. We present a near-complete spectral energy distribution (SED) for an extrasolar world: the T8 brown dwarf 2MASS J04151954‑0935066. Spanning from optical to mid-infrared (0.7–20.4 μm) wavelengths, the SED for this substellar atmosphere is constructed from new James Webb Space Telescope (JWST) NIRSpec G395H (R ∼ 2700) and Magellan Folded-port InfraRed Echellete (FIRE) echelle (R ∼ 8000) near-infrared spectra, along with MIRI mid-infrared photometry complemented by spectra from Keck I, Infrared Telescope Facility, Magellan, AKARI, Spitzer, and photometry from various surveys and missions. The NIRSpec G395H spectrum reveals strong molecular absorptions from NH3, CH4, H2S, CO2, and H2O at approximately 3.00, 3.35, 3.95, 4.25, and 5.00 μm, respectively, along with the presence of a CO absorption feature detected mainly at ∼4.6 μm. We detect no absorption of near-infrared K I doublets in the R ∼ 8000 FIRE spectra. In the mid-infrared Infrared Spectrograph spectrum, we tentatively identify a new CO2 feature at 14–16 μm. The comprehensive SED allows us to empirically constrain bolometric luminosity, effective temperature, mass, and radius. Additionally, we demonstrate that the NIRSpec G395H resolution, the highest allowable by JWST, enables a precise radial velocity measurement of 47.1 ± 1.8 km s‑1 for the object, in agreement with previous measurements.

Keywords: Brown dwarfs
A Hydrodynamical Simulations-based Model that Connects the FRB DM–Redshift Relation to Suppression of the Matter Power Spectrum via Feedback. Understanding the impact of baryonic feedback on the small-scale (k ≳ 1 h Mpc‑1) matter power spectrum is a key astrophysical challenge, and essential for interpreting data from upcoming weak-lensing surveys, which require percent-level accuracy to fully harness their potential. Astrophysical probes, such as the kinematic and thermal Sunyaev–Zel'dovich effects, have been used to constrain feedback at large scales (k ≲ 5 h Mpc‑1). The sightline-to-sightline variance in the fast radio bursts (FRBs) dispersion measure (DM) correlates with the strength of baryonic feedback and offers unique sensitivity at scales up to k ∼ 10 h Mpc‑1. We develop a new simulation-based formalism in which we parameterize the distribution of DM at a given redshift, p(DM∣z), as a log-normal with its first two moments computed analytically in terms of cosmological parameters and the feedback-dependent electron power spectrum Pee(k, z). We find that the log-normal parameterization provides an improved description of the p(DM∣z) distribution observed in hydrodynamical simulations as compared to the standard F-parameterization. Our model robustly captures the baryonic feedback effects across a wide range of baryonic feedback prescriptions in hydrodynamical simulations, including IllustrisTNG, SIMBA, and Astrid. Leveraging simulations incorporates the redshift evolution of the DM variance by construction and facilitates the translation of constrained feedback parameters to the suppression of matter power spectrum relative to gravity-only simulations. We show that with 104 FRBs, the suppression can be constrained to percent-level precision at large scales and ∼10% precision at scales k ≳ 10 h Mpc‑1 with prior-to-posterior 1σ constraint width ratio ≳20.

Keywords: Observational cosmology, Radio transient sources
Characterization of the Transmission and Generation of Turbulence at Interplanetary Shocks. We study the transmission and characteristics of turbulent magnetohydrodynamic (MHD) fluctuations from upstream to downstream regions of interplanetary (IP) shocks using the linear mode decomposition (LMD) technique of G. P. Zank et al. We perform a superposed epoch analysis (SEA) of 84 fast-forward quasi-perpendicular shock events observed by the Wind spacecraft at 1 au. We find that the intensities of various MHD modes associated with density, velocity, and magnetic field fluctuations are enhanced by ∼4–14 times across the shock. On average, the amplitude enhancement of velocity fluctuations across the shock is smaller than that of density and magnetic fluctuations. The frequency spectra reveal that the entropy, magnetic island, and Alfvén modes are the dominant contributors to the overall density, magnetic field, and velocity fluctuations, respectively, both upstream and downstream. The SEA reveals that the downstream spectral slope of various modes closely follows a f‑5/3 (or k‑5/3) power law, but the upstream spectra are slightly flatter than the downstream curves. A steeper spectral slope downstream suggests an increased energy dissipation or a stronger turbulent cascade. These findings show the usefulness of the LMD technique to decompose turbulent fluctuations into fundamental linear MHD modes, providing a deeper understanding of turbulence upstream and downstream of IP shocks.

Keywords: Interplanetary turbulence, Interplanetary shocks
CO Emission and Absorption-line Survey of the M87 Nucleus Using Archival ALMA Imaging. We present an M87 molecular line search from archival Atacama Large Millimeter/submillimeter Array imaging, covering the circumnuclear disk (CND) as well as ionized gas filaments and dusty cloud regions. We find no evidence for CO emission in the central ∼kiloparsec and place an upper limit of  MH2&lt;2.3×105 M⊙ in the atomic gas CND region, a factor of 20× lower than previous surveys. During this search, we discovered extragalactic CO absorption lines in the J = 1−0, 2−1, and 3−2 transitions against the bright (jansky-scale) active nucleus. These CO lines are narrow (∼5 km s−1) and blueshifted with respect to the galaxy's systemic velocity by −75 to −84 km s−1. This CO absorber appears to be kinematically distinct from outflowing atomic gas seen in absorption. Low integrated opacities ranging from τCO ∼ 0.02−0.06 km s−1 and a column density NCO ≍ (1.2 ± 0.2) × 1015 cm−2 translate to  NH2∼(1−2)×1020  cm−2. CO excitation temperatures spanning Tex ∼ 8─30 K do not follow local thermodynamic equilibrium (LTE) expectations, and non-LTE radex radiative transfer modeling of the CO absorber is consistent with a number density  nH2∼5000  cm−3 embedded in a ∼60 K environment. Taken together, the observed CO absorption lines are most consistent with a thin, pressure-confined filament seen slightly off-center from the M87 nucleus. We also explore the impact of residual telluric lines and atmospheric variability on narrow extragalactic line identification and demonstrate how bandpass calibration limitations may introduce broad but very low signal-to-noise ratio and spurious absorption and emission signatures.

Keywords: AGN host galaxies, Quasar absorption line spectroscopy, Galaxy nuclei, Active galactic nuclei, Interstellar medium, Radio active galactic nuclei
NuSTAR Detection of an Absorption Feature in ESP 39607: Evidence for an Ultrafast Inflow?. We report the serendipitous discovery of an absorption feature at 4.8 keV in the NuSTAR spectra of ESP 39607, a Seyfert 2 galaxy at z = 0.201, observed in 2023 May and 2024 August. The feature is detected in both observations with individual significance levels between 2σ and 3σ, computed with multiple statistical methods. The combined probability of detecting it in both observations is ≳4σ. The absorption feature is consistent with an ultrafast inflow (UFI) potentially associated with Fe XXV or Fe XXVI Kα transitions. The inferred inflow velocity is ∼0.15–0.20c, with an estimated launching radius of 22–89Rg, depending on the assumed iron transition and whether radiation pressure is accounted for. Photoionization modeling associates the UFI primarily with Fe XXV Kα absorption, blended with a minor contribution from Fe XXVI Kα. Alternative explanations, including associations with the warm-hot intergalactic medium or outflows of lighter elements, are investigated but found unlikely. If confirmed, this detection represents a rare example of a UFI, providing valuable evidence into extreme and/or nonstandard accretion processes near supermassive black holes. Follow-up observations with higher-resolution X-ray spectroscopy, such as with XMM-Newton or XRISM, will be essential to confirm the nature of this feature and better constrain the physical mechanisms driving it.

Keywords: Active galaxies, Active galactic nuclei, High-luminosity active galactic nuclei, X-ray active galactic nuclei
Origin of Radio Emission in Three Nearby Ultraluminous Infrared Galaxies with Signatures of Luminous Buried Active Galactic Nuclei. We report multifrequency Very Long Baseline Array (VLBA) observations at 2.3 and 8.4 GHz of three nearby ultraluminous infrared galaxies, identified via mid-infrared spectroscopic analyses as hosting deeply embedded active galactic nuclei (AGNs). Milliarcsecond-scale observations at both frequencies reveal compact continuum emission in IRAS F00188‑0856 and IRAS F01298‑0744, accounting for ∼10% of the flux density measured on arcsecond scales. The nondetection in IRAS F00091‑0738 and the lower limit on the intrinsic 8.4 GHz brightness temperature of 106.1 K in IRAS F01298‑0744 yield no conclusive evidence of AGN-driven radio emission, whereas the measurement of 107.8 K in IRAS F00188‑0856 confirms an AGN origin. Thus, the mid-infrared AGN classification remains robust, with at least one object exhibiting compact radio emission indicative of AGN activity. We further investigate the high-frequency spectral steepening observed in all three galaxies. In each case, this steepening arises from spectral aging in diffuse kiloparsec-scale emission, which is resolved out by the VLBA observations. One possible explanation for the steepening of the sample is merger-induced particle acceleration. IRAS F00188‑0856 exhibits a peaked radio spectrum, characteristic of a young radio source, with the high-frequency steepening attributable to this AGN activity. Consequently, the spectral steepening at high frequencies arises from particles accelerated by merger dynamics or AGN activity.

Keywords: Ultraluminous infrared galaxies, Very long baseline interferometry, Active galactic nuclei, Radio continuum emission, Interacting galaxies
Are Gas-rich Ultra-diffuse Galaxies and Field Dwarfs Distinct?. We explore the differences in gas-rich field ultra-diffuse galaxies (UDGs) and diffuse classical dwarf galaxies using an extensive atomic gas (H I) follow-up survey of optically selected UDG candidates from the Systematically Measuring Ultra-diffuse Galaxies (SMUDGes) catalogue. We also compare the SMUDGes-H I observations with two state-of-the-art cosmological hydrodynamical simulations: Numerical Investigation of a Hundred Astrophysical Objects (NIHAO), where UDGs form through a series of bursty star formation episodes and ROMULUS25, where UDGs form as a result of major mergers that temporarily increase their spin. Although the suggested formation scenarios for UDGs within these simulations are different, the present-day H I masses MH I, stellar masses M*, and star formation rates of simulated galaxies are qualitatively and quantitatively consistent with each other and with the observed SMUDGes-H I sample. We find that when controlling for M*, there is a positive correlation between the gas richness MH I/M* and the effective optical radius Reff, and that this trend is not different between the UDG and dwarf populations, within the measured scatter. Taken together, our results suggest that gas-rich, star-forming UDGs and dwarfs are not distinct galaxy populations, either observationally or in simulations.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy evolution, Low surface brightness galaxies
Comparing Star Formation Histories and Evolutionary Pathways of Post-starburst and E+A Galaxies in TNG50 and SDSS-IV MaNGA. E+A galaxies represent a class of recently quenched objects, with spectra that show evidence of a previous substantial starburst and strong Balmer absorption lines indicative of A-type stellar populations. Using an SDSS-IV MaNGA–selected sample of E+A galaxies, we identify a matching sample in the TNG50 simulation to study their evolutionary histories. Additionally, we identify a sample of generic post-starburst (PSB) galaxies based on their star formation histories (SFHs) from the MaNGA Pipe3D value-added catalog. We find that PSB-like SFHs make up a similar fraction of galaxies in TNG50 (0.9% compared to MaNGA's ∼1%). Matching galaxies based solely on their stellar masses and metallicities in TNG50 does not result in a sample with PSB-like histories. We analyzed the chemical enrichment histories of our selected simulated galaxy samples and found that both PSB and E+A galaxies exhibit a distinct episode of rapid enrichment when compared to galaxies in TNG50 with a similar stellar mass range. These galaxies are typically metal-poor before undergoing an extended ∼2 Gyr starburst, during which a phase of rapid chemical enrichment occurs over the first ∼300 Myr. The final systems are generally more metal-rich than the average galaxy in TNG50, while the MaNGA data do not show this trend. This suggests that PSB galaxies undergo unique evolutionary processes as they transition from starburst activity to quiescence. Further studies are needed to determine whether these galaxies originate from truly metal-poor progenitors and to better understand their subsequent evolution.

Keywords: Galaxy evolution, Post-starburst galaxies, E+A galaxies
BASS. XLVIII. [Ne V] λ3427 Emission in Powerful Nearby Active Galactic Nuclei. We investigate the high-ionization, narrow [Ne V] λ3427 line emission in a sample of over 340 ultrahard X-ray (14─195 keV) selected active galactic nuclei (AGN) drawn from the BAT AGN Spectroscopic Survey project. The analysis includes measurements in individual and stacked spectra and considers several key AGN properties such as X-ray luminosity, supermassive black hole (SMBH) mass, Eddington ratios, and line-of-sight column density. The [Ne V] λ3427 line is robustly detected in ≍43% (146/341) of the AGN in our sample, with no significant trends between the detection rate and key AGN/SMBH properties. In particular, the detection rate remains high even at the highest levels of obscuration (&gt;70% for  logNH/cm−2)≳23 ). On the other hand, even some of our highest signal-to-noise spectra (S/N &gt; 50) lack a robust [Ne v] detection. The typical (median) scaling ratios between [Ne v] line emission and (ultra)hard X-ray emission in our sample are  logL[NeV]/L14−150keV≃−3.75  and  logL[NeV]/L2−10keV≃−3.36 . The scatter on these scaling ratios, ≲0.5 dex, is comparable to, and indeed smaller than, what is found for other commonly used tracers of AGN radiative outputs (e.g., [O III] λ5007). Otherwise, we find no significant relations between the (relative) strength of [Ne v] and the basic AGN/SMBH properties under study, in contrast with simple expectations from models of SMBH accretion flows. Our results reaffirm the usability of [Ne v] as an AGN tracer even in highly obscured systems, including dual AGN and high-redshift sources.

Keywords: X-ray active galactic nuclei, Active galactic nuclei, High energy astrophysics, Galaxy nuclei
Linear Thermal Instability of a Condensing Gas–Particle Mixture, with Possible Application to Chondrites and Planetesimals. We study the stability of a hot saturated gas coexisting with condensed particles in an optically thin medium. Such a situation may be obtained downstream of a shock, at condensation fronts, or in vaporizing impacts. We show that the gas–particle mixture is subject to a thermal instability whereby a region of lower temperature and higher condensate density cools faster to condense faster. If the region of runaway condensation has a sound-crossing time shorter than its cooling time, then it accretes more mass, in gas and particles, from its higher-pressure surroundings. Numerical integration of the linearized perturbation equations demonstrates that this radiation–condensation instability can create particle clumps and voids out of a secularly cooling gas. Provided radiation can escape to cool particle overdensities, thermal instability can help assemble chondrite parent bodies out of the vaporized debris of asteroid collisions and form planetesimals generally.

Keywords: Chondrites, Asteroids, Astrophysical fluid dynamics, Carbonaceous chondrites, Protoplanetary disks, Planetesimals, Meteorites, Debris disks
Stellar Mass Calibrations for Local Low-mass Galaxies. The stellar masses of galaxies are measured from integrated light via several methods—however, few of these methods were designed for low-mass (M⋆ ≲ 108 M⊙) "dwarf" galaxies, whose properties (e.g., stochastic star formation, low metallicity) pose unique challenges for estimating stellar masses. In this work, we quantify the precision and accuracy at which stellar masses of low-mass galaxies can be recovered using UV/optical/IR photometry. We use mock observations of 469 low-mass galaxies from a variety of models, including both semi-empirical models (GRUMPY and UniverseMachine-SAGA) and cosmological baryonic zoom-in simulations (MARVELous Dwarfs and FIRE-2), to test literature color–M⋆/L relations and multiwavelength spectral energy distribution (SED) mass estimators. We identify a list of "best practices" for measuring stellar masses of low-mass galaxies from integrated photometry. We find that literature color–M⋆/L relations are often unable to capture the bursty star formation histories (SFHs) of low-mass galaxies, and we develop an updated prescription for stellar mass based on g ‑ r color that is better able to recover stellar masses for the bursty low-mass galaxies in our sample (with ∼0.1 dex precision). SED fitting can also precisely recover stellar masses of low-mass galaxies, but this requires thoughtful choices about the form of the assumed SFH: Parametric SFHs can underestimate stellar mass by as much as ∼0.4 dex, while nonparametric SFHs recover true stellar masses with insignificant offset (‑0.03 ± 0.11 dex). Finally, we also caution that noninformative (wide) dust attenuation priors may introduce M⋆ uncertainties of up to ∼0.6 dex.

Keywords: Galaxy masses, Dwarf galaxies, Galaxy photometry, Galaxies
Data-driven Radiative Hydrodynamics Simulations of the Solar Photosphere Using Physics-informed Neural Networks: Proof of Concept. Current, realistic numerical simulations of the solar atmosphere reproduce observations in a statistical sense; they do not replicate observations such as a movie of solar granulation. Inversions on the other hand reproduce observations by design, but the resulting models are often not physically self-consistent. Physics-informed neural networks (PINNs) offer a new approach to solving the time-dependent radiative hydrodynamics equations and matching observations as boundary conditions. PINNs approximate the solution of the integro-differential equations with a deep neural network. The parameters of this network are determined by minimizing the residuals with respect to the physics equations and the observations. The resulting models are continuous in all dimensions, can zoom into local areas of interest in space and time, and provide information on physical parameters that are not necessarily directly observed such as horizontal velocities. Here, we present the first proof of concept of this novel approach, explain the underlying methodology in detail, and provide an outlook to the many applications that PINNs enable.

Keywords: Hydrodynamical simulations, Solar physics, Astronomy data reduction, Neural networks
Spectroscopy of ClS<SUB>2</SUB> Isomers: Implications for Sulfur–Chlorine Chemistry. Chlorine–sulfur chemistry plays a significant role in the atmospheric processes of Venus, yet many aspects remain unclear, despite decades of study. This work presents a theoretical investigation into the photochemistry of ClSS and SClS isomers using high-level ab initio methods. ClSS is predicted to be the most stable isomer, exhibiting two significant absorption peaks at 384 and 243 nm. The 243 nm absorption may lead to photodissociation (yielding S, ClS, or S2) or fluorescence back to the ground state, while absorption at 384 nm produces Cl and S2. In contrast, SClS is predicted to be photochemically unstable. A comprehensive set of spectroscopic constants for both isomers is provided, to support future experimental detections and astronomical observations. Although atmospheric models of Venus suggest ClS2 abundances are likely too low, the calculated spectrum of ClSS shows significant overlap with the 320–400 nm range of Venus' enigmatic near-UV absorber. This study establishes essential spectroscopic benchmarks for ClS2 isomers, advancing our understanding of sulfur–chlorine photochemical networks in Venus and related environments.

Keywords: Planetary atmospheres, Venus
Spherically Symmetric Accretion with Self-gravity: Analytical Formulae and Numerical Validation. Spherically symmetric accretion incorporating self-gravity constitutes a three-point boundary value problem (TPBVP) governed by constraints at the outer boundary, sonic point, and accretor surface. Previous studies have two limitations: either employing an incorrect formula for self-gravity potential in analytical treatments, or introducing additional input parameters in numerical implementations to circumvent solving the full TPBVP. To address these issues, we present a self-consistent TPBVP formulation, solved using the relaxation method. We also derive approximate analytical formulae that enable rapid estimates of self-gravity effects. Our analysis identifies a dimensionless parameter  β≡2Gρ¯rout2/aout2  that characterizes the strength of self-gravity, where  ρ¯  and rout are the mean density and outer radius of the flow, respectively, and aout is the adiabatic sound speed of the external medium. For practical estimation,  ρ¯  may be approximated by the external medium density ρout. We identify an upper limit for β, beyond which steady accretion becomes unsustainable—a behavior consistent with classical gravitational instability that previous studies failed to capture. The accretion rate enhancement decreases monotonically as the adiabatic index γ increases. For γ = 5/3, self-gravity ceases to augment the accretion rate. These theoretical predictions are validated by our numerical solutions. We further apply our results to two astrophysical scenarios: hyper-Eddington accretion onto supermassive black hole seeds in the early Universe, where self-gravity is significant; and accretion onto stellar-mass objects embedded in active galactic nuclei disks, where self-gravity is non-negligible under certain conditions and should be evaluated using β.

Keywords: Accretion, Bondi accretion, Hydrodynamics, Gravitation