Sazuna/UAT_keywords huggingface dataset:
Accretion-regulated Type Transitions in Changing-look AGNs: Evidence from Two-epoch Spectral Analysis. The changing-look active galactic nucleus (CL-AGN), an extraordinary subpopulation of supermassive black holes, has attracted growing attention to understand its nature. We present an analysis of the spectral properties of 203 low-redshift CL-AGNs (z &lt; 0.35) using two-epoch spectra from Sloan Digital Sky Survey DR16 and DESI DR1 with time baseline ranging from ∼1000 to 8000 days, based on spectral fitting and decomposition. The sample consists of 11.3% type 1.0, 26.6% type 1.2, 43.1% type 1.5, and 19% type 1.8/2.0 AGNs. The total sample is divided into two data sets: Data Set A (110 objects) with minor spectral type variations, likely general AGN variability, and Data Set B (93 objects) showing significant type transitions and characteristic turn-on or turnoff behavior. Our results reveal clear optical continuum and emission-line variability, showing both "bluer-when-brighter" and "redder-when-brighter" trends. A strong correlation between the broad Hβ/[O III] ratio and broad Hα luminosity (LHα),  log(Hβ/[OIII])=   (0.63±0.07)log(LHα)−  (26.49 ± 2.96) ± 0.48 for Data Set B, as well as the correlation between Hβ/[O III] and Eddington ratio (Lbol/LEdd),  log(Hβ/[OIII])=   (0.59±0.08)log(Lbol/LEdd)+  (1.02 ± 0.15) ± 0.53 for Data Set B, suggests that accretion rate variations drive changes in ionizing flux within the broad-line region, thereby triggering AGN type transitions. These findings underscore the critical role of supermassive black hole accretion processes in refining the AGN unification model. Future work should investigate potential connections between stellar evolution in outer accretion disk and the observed scatter in these correlations.

Keywords: Accretion, Active galaxies, Active galactic nuclei, Time domain astronomy, Galaxy evolution
AI-powered Reconstruction of Dark Matter Velocity Fields from Redshift-space Halo Distribution. We propose a UNet-based deep learning model to reconstruct the real-space dark matter (DM) velocity field from the redshift-space distribution of sparse DM halos. Using various statistical measures, we show that the reconstructed velocity components—including velocity magnitude, momentum, and divergence—closely match the ground truth, achieving better than 10% relative error and a correlation coefficient of 0.88. In the power spectrum comparison over k ∈ [0.05, 0.3] h Mpc−1, the UNet reconstruction outperforms linear theory and agrees with the true field within 2σ. The model also effectively corrects redshift-space distortions (RSD), yielding unbiased power spectrum multipoles of DM fields within 2σ. Notably, UNet remains robust even with incomplete halo mass information. These results highlight the model's broad applicability to cosmological analyses, including RSD, cosmic web studies, the kinetic Sunyaev─Zel'dovich effect, and baryon acoustic oscillation reconstruction.

Keywords: Cosmology, Large-scale structure of the universe
Dynamical Properties and Velocity Dispersion─Mass Relation of z ∼ 1 Galaxy Clusters from the GOGREEN and GCLASS Surveys. We investigate a sample of 14 galaxy clusters from the GOGREEN and GCLASS (GG) spectroscopic data sets within the redshift range 0.87 ≤ z ≤ 1.37 and cluster masses M200 ≳ 2 × 1014h−1M⊙. Using the highly effective GalWeight technique for cluster membership assignment developed by our own team, we derive the dynamical parameters of these clusters through the virial mass estimator. We examine the velocity dispersion─cluster mass relation (σMR) for the GG cluster sample. We find  logσ200=(2.94±0.02)+(0.37±0.09)logM200  with an intrinsic scatter of σint = 0.02 ± 0.02. Our results demonstrate that the σMR relation is consistent with predictions from cosmological simulations, highlighting the reliability of the GalWeight technique for cluster membership assignment. Furthermore, the σMR validates the robustness of the virial mass estimator in accurately recovering cluster masses and associated parameters. Importantly, our findings confirm that velocity dispersion can be used directly to estimate cluster mass without relying on dynamical mass estimators.

Keywords: Galaxy clusters, N-body simulations, Scaling relations, High-redshift galaxy clusters
GATOS. VIII. On the Physical Origin of the Extended Mid-infrared Emission in Active Galactic Nuclei. The polar mid-infrared (MIR) emission detected within tens to hundreds of parsecs in some active galactic nuclei (AGN) has been associated with dusty winds driven away by radiation pressure. The physical characterization of this extended polar emission remains uncertain. Here, we combine 10─21 μm JWST/Mid-InfRared Instrument (MIRI) imaging observations with 7─25 μm JWST/MIRI MRS integral field spectroscopic observations of six nearby,  D̄=35.4±4.6  Mpc, AGN from the GATOS Survey to quantify the nature of the extended MIR emission at ∼75 pc resolution at 21 μm. These AGN have similar bolometric luminosities,  log10(L̄bol[ergs−1])=44.0±0.3 , span a wide range of optical outflow rates,  Ṁ=  0.003─0.21 M⊙ yr−1, column densities,  log10(NHX−ray[cm−2])=  22.2─24.3, and Eddington ratios, λEdd = 0.005─0.06. We cross-correlate the line-only and continuum-only images and find a poor correlation, which indicates that the extended MIR continuum emission is spatially uncorrelated with the warm outflows associated with narrow emission lines within 10─15 μm. Line emission is resolved along the jet axis, while dust emission is perpendicular to it. The 75─450 pc continuum emission has a fairly constant dust temperature,  Td=132−7+7  K, and mass,  Md=728−27+29  M⊙. Using the conditions of energy balance between radiation-pressure and gravity (λEdd versus NH), we find that our AGN sample is in the gravitationally bounded regime consistent with no detection of dusty winds. At 10 μm, the level of extended line emission contribution is correlated with the outflow kinetic energy and mass outflow rates. We find no correlation with the AGN properties. These results indicate that the radio jet may be triggering the gas outflow and line emission, while the extended dust emission is distributed in molecular clouds and/or shocked regions.

Keywords: Infrared astronomy, Active galactic nuclei, Dust continuum emission
Beyond the Local Group. I. Cosmic Filaments Govern the Spatial Alignments of Galaxy Pairs. Using a large observational sample from the Sloan Digital Sky Survey, we investigate the spatial alignment between galaxy pairs and their local cosmic filaments. Focusing on pairs with stellar masses and separations comparable to the Milky Way─Andromeda (MW─M31) system, we measure the angle between the pair connecting line and the orientation of the host filament, determined using a filament catalog constructed via the Bisous model. Our analysis reveals a statistically significant tendency of galaxy pairs to align their connecting lines along their host filaments, manifesting as an overall ∼7% excess of alignment angles smaller than the MW─M31 case compared to a random distribution. Crucially, the strength of this alignment exhibits a strong dependence on the distance to the filament spine. Pairs located within 0.2 Mpc from the filament spine show the strongest alignment, while those beyond 1 Mpc display no significant alignment. Furthermore, we identify a bimodal distribution of alignment angles near filament cores, suggesting distinct dynamical populations potentially associated with infall and interaction processes. Our results provide robust observational support for theoretical models in which anisotropic accretion and tidal forces within the cosmic web drive galaxy pair evolution. They also position the MW─M31 system as a representative filament-aligned pair, offering insights into Local Group assembly. This study demonstrates the cosmic web's critical role in dictating pair orientations and motivates future work with kinematic data to unravel galaxy─environment interplay.

Keywords: Local Group, Galaxy formation, Galaxy environments, Large-scale structure of the universe, Cosmic web
Statistical Overview of Long-lived Active Regions Observed across Multiple Carrington Rotations. The study of solar active regions (ARs) is of central importance to a range of fundamental science, as well as the practical applications of space weather. AR emergence and life cycles are two areas of particular interest, yet the lack of consistent full-Sun observations has made long-term studies of ARs difficult. Here, we present results from a study to identify and characterize long-lived active regions (LLARs), defined as those which were observed during at least two consecutive Carrington rotations and that did not undergo significant successive flux emergence once the decay phase began. Such ARs accounted for 13% of all NOAA-identified ARs between 2011 and 2019, and their distribution closely follows the annual sunspot number. This implies that LLARs are produced by the same basic driving processes as regular ARs. LLAR areas tend to be significantly larger and contain more magnetic flux compared to other ARs, but the two categories have similar magnetic complexity distributions. The most striking result, however, is that LLARs are 3─6 times more likely than other ARs to be the source of a solar flare of GOES class C or greater. This highlights the importance of studying what makes a LLAR and how to identify them at emergence with a view toward improved space weather forecasting. The further implications of these findings for AR heating spatial and temporal patterns will be explored in an upcoming study.

Keywords: Solar cycle, Solar active region magnetic fields, Solar coronal heating, Solar active regions, Solar magnetic fields, Active solar corona
A Host Galaxy Morphology Link between Quasiperiodic Eruptions and Tidal Disruption Events. The physical processes that produce X-ray quasiperiodic eruptions (QPEs) recently discovered from the nuclei of several low-redshift galaxies are mysterious. Several pieces of observational evidence strongly suggest a link between QPEs and tidal disruption events (TDEs). Previous studies also reveal that the morphologies of TDE host galaxies are highly concentrated, with high Sérsic indices, bulge-to-total-light ratios, and stellar surface mass densities relative to the broader galaxy population. We use these distinctive properties to test the link between QPEs and TDEs by comparing these parameters of QPE host galaxies to TDE host galaxies. We employ archival Legacy Survey images of a sample of 9 QPE host galaxies and a sample of 13 TDE host galaxies and model their surface brightness profiles. We show that QPE host galaxies have high Sérsic indices of ∼3, high bulge-to-total-light ratios of ∼0.5, and high surface mass densities of ∼1010 M⊙ kpc−2. These properties are similar to TDE host galaxies but are in strong contrast to a mass- and redshift-matched control sample of galaxies. We also find tentative evidence that the central black holes in both QPE and TDE host galaxies are undermassive relative to their stellar mass. The morphological similarities between QPE and TDE host galaxies at the population level add to the mounting evidence of a physical link between these phenomena and favor QPE models that also invoke TDEs.

Keywords: X-ray astronomy, Tidal disruption, Galaxies
Evolution of Lunar Orbit under Climate Dynamics since the Last Glacial Cycle. Understanding the long-term evolution of lunar orbit is an essential task in astronomy and astrophysics because lunar and planetary ephemerides are indispensable in many important applications, such as spacecraft navigation and reference frame transformations. Recently, it has been suggested that climate dynamics, particularly sea level change due to melting of polar ice sheets, can subtly modulate ocean tides, thus altering the tidal dissipation and lunar recession rate by ∼2.6% in the 21st century. In our study, we provide a correction to standard models of lunar orbital evolution relevant for astrophysical applications. We use the reconstructed history of ice thickness, paleotopography, and sea level change since the last glacial cycle (∼122,000 yr ago) and adopt a revised tidal dissipation model to argue that the climate-induced changes in the lunar orbit might not be negligible and have likely altered the Earth─Moon distance by variable rates as large as ∼0.9 mm yr−1, which occur on top of the background trend of ∼38.3 mm yr−1. However, this is currently absent from dynamical models of lunar evolution. Our results suggest that lunar orbit ephemerides might need to be revised by at least ∼1.5%─2.3% in order to obtain a more accurate representation of the tidal dynamics and orbital motions. The model proposed in this paper might also be relevant for other astrophysical bodies, such as exoplanetary satellites.

Keywords: Tides, Celestial mechanics, Ephemerides, Astrometry
Local Particle Acceleration in an ICME-in-Sheath Structure Observed by Solar Orbiter. Local particle acceleration in the shock sheath region formed during the interaction between multiple coronal mass ejections (CMEs) is a complicated process that is still under investigation. On 2024 March 23, the successive eruption of two magnetic flux ropes from the solar active region 3614 produced twin CMEs, as identified in coronagraph images. By analyzing in situ data from Solar Orbiter and Wind, it is found that the primary interplanetary CME (ICME)-driven shock overtook the preceding ICME, trapping it in the sheath between the shock and the primary ICME, forming the ICME-in-sheath (IIS) structure. Using Solar Orbiter observations, we show that both electrons and ions are accelerated within the IIS. A clear enhancement of suprathermal electrons was observed at the IIS boundary, where strong flow shear and large magnetic field variation suggest possible local electron acceleration. Electrons (&gt;38 keV) exhibit a long-lasting enhancement in the IIS with a spectral index of ∼2.2, similar to that in the shock sheath and the primary ICME, indicating a similar solar origin. Inside both the sheath and IIS, spectra of protons and 4He are generally consistent with the prediction of the diffusive shock acceleration, whereas Fe and O present a double power-law shape. Additionally, the Fe/O ratio in the IIS is higher than that in the sheath, and closer to the abundance of the flare-related particles, suggesting the remnant particles of flare confined in the IIS.

Keywords: Solar energetic particles, Interplanetary shocks, Solar coronal mass ejections
Testing Photometric Techniques for Measuring the Rest-frame UV Spectral Slope against JWST PRISM Spectroscopy. We present a sample of 53 galaxy spectra at zSPEC ∼ 5─12 from the JWST CEERS and RUBIES surveys, combining NIRSpec PRISM spectroscopy with NIRCam photometry. We aim to use these data to establish best practices for measuring the UV spectral slope (β) in the era of JWST. We adopt power-law fits to the rest-frame UV continuum from the spectroscopic data as our fiducial, or "true," β values, and compare them to photometric estimates derived through three methods: (1) photometric power-law fitting, (2) power-law fitting to a spectral energy distribution (SED) model fitted to the photometry, (3) single-color fitting near the Lyman break, and (4) single-color fitting at fixed rest-frame wavelengths. We find that photometric power-law fitting and SED fitting are comparable and most closely recover the spectroscopic slopes, with minimal bias and scatter. Single-color estimates, while commonly used in past studies, show the most significant deviations and are not recommended when more than a single color is available. Our results highlight the limitations and strengths of each approach and provide practical guidance for measuring β from photometry when spectra are unavailable or are of insufficient quality.

Keywords: Early universe, Galaxy formation, Ultraviolet spectroscopy, Galaxy evolution, Astronomical methods
Quest for a Coherent Definition of Weak-line Quasars and Its Physical Implications. Weak-line quasars (WLQs) represent a subset of type 1 quasars distinguished by remarkably weak high-ionization broad emission lines, yet exhibiting normal optical/UV continua. This study establishes a physically motivated definition of WLQs using 371,091 quasars from the Sloan Digital Sky Survey Data Release 16 catalog. By analyzing outliers in three key relations, the L1350 Å─C IV blueshift relation, the Baldwin effect, and the  logL2500Å−αox  relation, we identify two critical thresholds in C IV equivalent width (EW): 8.9 ± 0.2 Å and 19.3 ± 0.3 Å. Quasars with EW(C IV) &lt; 8.9 ± 0.2 Å are defined as WLQs, exhibiting enhanced C IV blueshifts, significant deviations from the Baldwin effect, and a high fraction of X-ray weak objects (nearly half of this population). Quasars with EW(C IV) &gt; 19.3 ± 0.3 Å show normal quasar properties, while objects with intermediate C IV EW (8.9─19.3 Å) are defined as "bridge quasars," showing transitional behaviors. Systematic analysis of emission-line attenuation of WLQs reveals a clear positive correlation between the attenuation factor and ionization energy, with high-ionization lines (HILs; e.g., He II, C IV) suppressed by factors of ∼3σ─4σ compared to low-ionization lines (LILs; e.g., Mg II, O I). This ionization-stratified attenuation supports the shielding gas model, where geometrically thick inner accretion disk obscures high-energy photons, suppressing HIL emission, while the LILs remain less affected. Based on this accretion-disk geometry, we argue that WLQs and normal quasars defined in our framework generally correspond to the slim disk and standard thin disk regimes, respectively, while the bridge quasars represent a transitional phase between the two states. This work establishes a unified observational criterion for WLQs and discusses their physical implications, highlighting the role of accretion-driven shielding gas in shaping their unique spectral features.

Keywords: Accretion, Supermassive black holes, Quasars, Active galactic nuclei, Line intensities
Dynamical Masses for 23 Pre-main-sequence Stars in Upper Scorpius: A Critical Test of Stellar Evolutionary Models. We present dynamical masses for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius star-forming region. These masses were derived from the Keplerian rotation of CO disk gas using the Markov Chain Monte Carlo radiative-transfer package pdspy and a flared-disk model with 15 free parameters. We compare our dynamical masses to those derived from five PMS evolutionary models, and find that most models consistently underestimate stellar mass by ≳25%. Models with updated treatment of stellar magnetic fields are a notable exception—they consistently return stellar masses in good agreement with the dynamical results. We find that the magnetic models' performance is valid even at low masses, in contrast with some literature results suggesting they may overestimate stellar mass for M⋆ ≲ 0.6 M⊙. Our results are consistent with dynamical versus isochronal evaluations for younger samples (e.g., Taurus, 1─3 Myr), and extend the systematic evaluation of stellar evolutionary models up to stars ∼11 Myr in age. Finally, we derive disk dust masses to evaluate whether using dynamical masses versus isochronal masses changes the slope of the log(Mdust)−log(M⋆) relation. We derive a slightly shallower relation using dynamical masses versus isochronal masses, but the slopes of these relations agree within uncertainties. In all cases, we derive a steeper than linear relation for log(Mdust)−log(M⋆), consistent with previous literature results for Upper Sco.

Keywords: Astronomy data modeling, Pre-main sequence stars, Star formation, Protoplanetary disks, Stellar masses, Radio interferometry
Stellar Mass Assembly History of Massive Quiescent Galaxies since z ∼ 4: Insights from Spatially Resolved Spectral Energy Distribution Fitting with JWST Data. Massive quiescent galaxies at high redshift show significantly more compact morphology than their local counterparts. To examine their internal structure across a wide redshift range and investigate potential redshift dependence, we performed spatially resolved spectral energy distribution fitting using piXedfit software on massive  (log(M*/M⊙)∼11)  quiescent galaxies at 0 &lt; z &lt; 4 with public James Webb Space Telescope and Hubble Space Telescope imaging data from the Public Release Imaging for Extragalactic Research and the Cosmic Evolution Early Release Science Survey. We find that at z ∼ 3.5 the half-mass radius is about 5.4 times smaller than at z ∼ 0.5. This growth is driven by stellar mass buildup in the outskirts (r &gt; 4 kpc), while the central regions (r ∼ 1 kpc) remain largely unchanged, with stellar mass surface density similar to local quiescent galaxies. The estimated star formation rates are too low to explain the stellar mass growth, indicating that an additional stellar mass accumulation process, such as mergers, is necessary. We parameterize the size─mass relation of the most massive galaxies in our sample as  log(Re,mass)∝αlog(M*)  and find  α=2.67−1.17+1.14  for z ⪅ 2, consistent with growth dominated by minor mergers, and  α=0.91−0.16+0.20  for z ⪆ 2, consistent with growth dominated by major mergers. These results indicate that massive quiescent galaxies originate from compact quenched systems and grow through combinations of minor and major mergers.

Keywords: Quenched galaxies, Galaxy evolution, Galaxy quenching, High-redshift galaxies, Galaxies
Discovery of Changing-look Behavior in AGN NGC 3822: A Long-term Multiwavelength Study. We present a comprehensive long-term multiwavelength study of the active galactic nucleus NGC 3822, based on 17 yr (2008─2025) of X-ray, ultraviolet (UV), and optical observations. The data set includes observations from Swift, XMM-Newton, and NuSTAR, the Very Large Telescope, and the Himalayan Chandra Telescope. Our multiwavelength light-curve analysis reveals flux variations across X-ray to optical/UV bands, with an increased variability amplitude at shorter wavelengths. X-ray spectral analysis indicates the presence of intrinsic absorption during the 2016 and 2022 observations; however, this absorption disappeared before and after these epochs. The presence and absence of the absorber are attributed to clouds moving in and out of the line of sight. During the long-term monitoring period, the bolometric luminosity of the source varies between (1.32 and 17) × 1043 erg s−1. Optical spectroscopic monitoring reveals changing-look (CL) behavior in NGC 3822, characterized by the appearance and disappearance of broad emission lines (BELs). These CL transitions are associated with changes in the Eddington ratio rather than changes in the obscuration. The BELs appear only when the Eddington ratio is relatively high (∼3.8 × 10−3) and disappear when it drops to a lower value (∼0.9 × 10−3).

Keywords: Seyfert galaxies, X-ray active galactic nuclei, Active galactic nuclei