Sazuna/UAT_keywords huggingface dataset:
Effects of Intrinsic Active Galactic Nucleus Variability on Optical Quasiperiodic Oscillations Related to Subparsec Binary Black Hole Systems in Broad-line Active Galactic Nuclei. In this paper, an oversimplified model is proposed to test the effects of intrinsic active galactic nucleus (AGN) variability on expected optical quasiperiodic oscillations (QPOs) related to subparsec binary black hole systems (BBHs) in broad-line AGN. The commonly accepted continuous autoregressive process is applied to describe intrinsic AGN variability related to each BH accreting system in a subparsec BBH system. Considering obscurations related to orbital rotations with periodicity Tp, artificial light curves including signals for optical QPOs can be built. Then, comparing the intrinsic periodicities Tp with the measured robust periodicities To through the artificial light curves, we find distributions of Tp/To have four significant peaks around 1, 2, 3, and 4, leading less than half of the artificial light curves to have consistency between To and Tp. Moreover, different collected model parameters have few effects on the distributions of Tp/To, indicating the effects of intrinsic AGN variability on optical QPOs are significantly strong and stable. Furthermore, after checking properties of optical QPOs in the light curves with different time steps, we find there are tiny effects of time steps on optical QPOs.

Keywords: Supermassive black holes, Active galactic nuclei, Lomb-Scargle periodogram, Periodic orbit
Constraining Reionization with Lyα Damping-wing Absorption in Galaxy Spectra: A Machine Learning Model Based on Reionization Simulations. Recently, NIRSpec PRISM/CLEAR observations by JWST have begun providing rest-frame UV continuum measurements of galaxies at z ≳ 7, revealing signatures of Lyα damping-wing (DW) absorption by the intergalactic medium (IGM). We develop a methodology to constrain the global ionization fraction of the IGM (QHII) using low-resolution spectra, employing the random forest classification (RFC) method. We construct mock spectra using the simulated galaxies and the IGM from the Cosmic Dawn II simulation and train RFC models to estimate QHII at the redshift of the source and to detect the presence of a damped Lyα absorber. We find that individual galaxy spectra with spectral bins between 1220 and 1270 Å and with signal-to-noise ratios (SNR) &gt;20 can place tight constraints on QHII, provided the UV continuum is accurately modeled. This method is particularly effective for the early phase of reionization (QHII &lt; 50%), when the IGM opacity is high in the DW. As a demonstration, we apply our model to existing NIRSpec PRISM/CLEAR spectra, placing upper bounds of QHII = 59.6%, 5.6%, and 18.5% at z = 7.7, 9.4, and 10.6, respectively, with 68% confidence, though several modeling uncertainties remain to be discussed. These constraints favor late-starting reionization models, where ≳80% of the IGM is ionized after z = 8. We conclude that high-SNR observations of carefully selected targets around z ∼ 7–9 can effectively constrain reionization models.

Keywords: Early universe, Origin of the universe, Radiative transfer simulations, Reionization, Random Forests
The Dwarf Irregular Galaxy NGC 6822. II. Young, Intermediate and Old Stellar Populations: Comparison between Theory and Observations. This paper presents a quantitative analysis of the stellar content in the Local Group dwarf irregular galaxy NGC 6822 by comparing stellar evolution models and observations in color─magnitude diagrams (CMDs) and color─color diagrams (CC-Ds). Our analysis is based on optical ground-based g, r, i photometry, and deep archival Hubble Space Telescope photometry of two fields in the galactic disk. We compared young, intermediate-age, and old stellar populations with isochrones from the BaSTI-IAC library and found that NGC 6822 hosts a quite metal-rich ([Fe/H] = −0.7 to −0.4) young component with an age ranging from 20─100 Myr. The intermediate-age population experienced a modest chemical enrichment between 4 and 8 Gyr ago, while stars older than 11 Gyr have a low metal abundance ([Fe/H] ∼ −1.70). We also identified the asymptotic giant branch (AGB) clump population with a luminosity peak at i ∼ 23.35 mag. Our analysis of both the CMD and the optical─near-IR (NIR)─mid-IR (MIR) CC-Ds of AGB oxygen- and carbon-rich stars, using the PARSEC+COLIBRI isochrones with and without circumstellar dust, reveals that this stellar component exhibits a spread in age from 1─2 Gyr and in metallicity between [Fe/H] = −1.30 and −1.70. The stellar models we used reproduce very well the two distinct color sequences defined by AGB O- and C-rich stars in the various optical─NIR─MIR CC-Ds, suggesting that they are reliable diagnostics to identify and characterize intermediate-age stellar populations. However, we also find that evolutionary prescriptions in the optical i-(r − i) CMDs predict, at fixed color, systematically lower luminosities than observed AGB stars.

Keywords: Stellar photometry, Dwarf irregular galaxies, Asymptotic giant branch stars, Stellar populations
Effects of Galactic Environment on Size and Dark Matter Content in Low-mass Galaxies. We utilize the cosmological volume simulation FIREbox to investigate how a galaxy's environment influences its size and dark matter content. Our study focuses on approximately 1200 galaxies (886 central and 332 satellite halos) in the low-mass regime, with stellar masses between 106 and 109M⊙. We analyze the size─mass relation (r50─M⋆), the inner dark matter mass─stellar mass ( ─M⋆) relation, and the halo mass─stellar mass (Mhalo─M⋆) relation. At fixed stellar mass, we find that galaxies experiencing stronger tidal influences, indicated by higher Perturbation Indices (PI &gt; 1) are generally larger and have lower halo masses relative to their counterparts with lower Perturbation Indices (PI &lt; 1). Applying a Random Forest regression model, we show that both the environment (PI) and halo mass (Mhalo) are significant predictors of a galaxy's relative size and dark matter content. Notably, because Mhalo is also strongly affected by the environment, our findings indicate that environmental conditions not only influence galactic sizes and relative inner dark matter content directly, but also indirectly, through their impact on halo mass. Our results highlight a critical interplay between environmental factors and halo mass in shaping galaxy properties, affirming the environment as a fundamental driver in galaxy formation and evolution.

Keywords: Galaxy formation, Dwarf galaxies, Galaxy evolution, Scaling relations
Are Purely Gaseous Bars in Dwarf Irregulars a Myth?. About two-thirds of galactic disks exhibit a central ellipsoidal stellar component called the bar, with or without a gaseous counterpart. However, there are a few dwarf galaxies with purely gaseous bars: NGC 3741, NGC 2915, and DDO 168. This is a puzzle, as gas is a collisional medium, and a gaseous bar is expected to be ripped off by shock waves. We study the formation of gaseous bars in these galaxies by constructing dynamical models constrained by stellar photometry and H I observations already available. We first analytically study the dynamical stability of the galactic disks against global m = 2 perturbations. Our results indicate that the stellar and gas disks are moderately unstable against these bar modes. Using N-body + hydrodynamical simulations employing RAMSES, we next find that a purely gaseous bar is formed in an oblate dark matter halo of vertical-to-planar axis ratio c/a = 0.6–0.8, with a relatively high-spin parameter Λ = 0.04–0.07, which survives for more than 10 dynamical times. Further, the low values of our calculated Mach numbers M = 2–6 of the gaseous medium comply with the survival of the gaseous bars, unaffected by shock waves. Interestingly, our simulations show the formation of a tiny stellar bar in each case. However, the temporal evolution of the change in angular momentum Lz of the different disk components indicates the exchange of Lz between the gas disk and the dark matter halo only; the Lz of the stellar disk remained unchanged, indicating a weak stellar bar.

Keywords: Galaxy dark matter halos, Galaxy formation, Galaxy bars, Galaxy dynamics, Galaxy kinematics, Galaxy evolution
oMEGACat. VI. Analysis of the Overall Kinematics of Omega Centauri in 3D: Velocity Dispersion, Kinematic Distance, Anisotropy, and Energy Equipartition. Omega Centauri (ω Cen) is the Milky Way's most massive globular cluster and is likely the stripped nucleus of an accreted dwarf galaxy. In this paper, we analyze ω Cen's kinematics using data from oMEGACat, a comprehensive catalog of ω Cen's central regions, including 1.4 million proper motion measurements and 300,000 spectroscopic radial velocities. Our velocity dispersion profiles and kinematic maps are consistent with previous work but improve on their resolution, precision, and spatial coverage. The cluster's 3D dispersion is isotropic in the core, with increasing radial anisotropy at larger radii. The 2D kinematic maps show an elongation of the velocity dispersion field comparable to the flattening observed photometrically. We find good agreement between proper motions and line-of-sight velocity dispersion, and we measure a kinematic distance of 5494 ± 61 pc, the most precise kinematic distance to ω Cen available. The subset of data with precise metallicity measurements shows no correlation between metallicity and kinematics, supporting the picture of well-mixed stellar populations within the half-light radius of ω Cen. Finally, we study the degree of energy equipartition using a large range of stellar masses. We find partial energy equipartition in the center that decreases towards large radii. The spatial dependence of the radial energy equipartition is stronger than the tangential energy equipartition. Our kinematic observations can serve as a new reference for future dynamical modeling efforts that will help to further disentangle the complex mass distribution within ω Cen.

Keywords: Globular star clusters, Stellar kinematics, Galaxy nuclei, Proper motions, Astrometry, Radial velocity
The Detection of H<SUB>2</SUB>O Maser Emission from Mid-IR Red Galaxies. We report the detection of H2O maser emission in 4 out of 77 (5.2%) mid-IR red galaxies that meet the color criteria of W1 ‑ W2 &gt; 0.5 and W1 ‑ W4 &gt; 7 and are classified as Type 2 active galactic nuclei (AGNs) based on optical, near-IR, and mid-IR spectral energy distribution (SED) fitting. Here, W1, W2, and W4 represent the IR magnitudes at 3.4, 4.6, and 22 μm, respectively, as measured by the Wide-field Infrared Survey Explorer. Three of the four newly identified maser galaxies are classified as either Seyfert 2 or low-ionization nuclear emission-line region systems, but none are disk maser systems. Our analysis indicates that AGN identifications based solely on SED fitting are unreliable, resulting in an unexpectedly low megamaser detection rate. By restricting our sample to optically classified Type 2 AGNs that satisfy the mid-IR color criteria, we achieve a maser detection rate of ∼13%–18%, aligning with previous predictions for mid-IR red sources. These selection criteria are one of the most effective methods to date for facilitating new maser detections, particularly in light of the recent identification of additional Type 2 AGNs identified from ongoing galaxy and AGN surveys.

Keywords: Hubble constant, Supermassive black holes, Astrophysical masers
An Oxidation Gradient Straddling the Small Planet Radius Valley. We present a population-level view of volatile gas species (H2, He, H2O, O2, CO, CO2, CH4) distribution during the sub-Neptune to rocky planet transition, revealing in detail the dynamic nature of small planet atmospheric compositions. Our novel model couples the atmospheric escape model IsoFATE with the magma ocean-atmosphere equilibrium chemistry model Atmodeller to simulate interior-atmosphere evolution over time for sub-Neptunes around G, K, and M stars. Chiefly, our simulations reveal that atmospheric mass fractionation driven by escape and interior-atmosphere exchange conspire to create a distinct oxidation gradient straddling the small-planet radius valley. We discover a key mechanism in shaping the oxidation landscape is the dissolution of water into the molten mantle, which shields oxygen from early escape, buffers the escape rate, and leads to oxidized secondary atmospheres following mantle outgassing. Our simulations reproduce a prominent population of He-rich worlds along the upper edge of the radius valley, revealing that they are stable on shorter timescales than previously predicted. Our simulations also robustly predict a broad population of O2-dominated atmospheres on close-in planets around low-mass stars, posing a potential source of false positive biosignature detection and marking a high-priority opportunity for the first-ever atmospheric O2 detection. We motivate future atmospheric characterization surveys by providing a target list of planet candidates predicted to have O2-, He-, and deuterium-rich atmospheres.

Keywords: Exoplanet atmospheric composition , Planetary system evolution, Exoplanets, Planetary atmospheres, Astrochemistry, Exoplanet astronomy, M stars, Planetary climates, Planetary science, Planetary interior, Exoplanet atmospheres, Exoplanet atmospheric evolution
The JWST View of Cygnus A: Jet-driven Coronal Outflow with a Twist. We present first results from James Webb Space Telescope Near-Infrared Spectrograph, Mid-Infrared Instrument, and Keck Cosmic Webb Imager integral field spectroscopy of the powerful but highly obscured host galaxy of the jetted radio source Cygnus A. We detect 169 infrared emission lines at 1.7–27 μm and explore the kinematics and physical properties of the extended narrow-line region (NLR) in unprecedented detail. The density-stratified NLR appears to be shaped by the initial blow-out and ongoing interaction of the radio jet with the interstellar medium, creating a multiphase bicone with a layered structure composed of molecular and ionized gas. The NLR spectrum, with strong coronal emission at kiloparsec scale, is well modeled by active galactic nucleus photoionization. We find evidence that the NLR is rotating around the radio axis, perhaps mediated by magnetic fields and driven by angular momentum transfer from the radio jet. The overall velocity field of the NLR is well described by 250 km s‑1 outflow along biconical spiral flow lines, combining both rotation and outflow signatures. There is particularly bright [Fe II] λ1.644 μm emission from a dense, high-velocity dispersion, photoionized clump of clouds found near the projected radio axis. Outflows of 600–2000 km s‑1 are found in bullets and streamers of ionized gas that may be ablated by the radio jet from these clouds, driving a local outflow rate of 40M⊙ yr‑1.

Keywords: Active galaxies, Radio jets, Radio galaxies
Search for Continuous Gravitational Waves from Known Pulsars in the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run. Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of general relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO─Virgo─KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering single-harmonic and dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the asymmetry in the neutron star mass distribution. For the single-harmonic emission model, 29 targets have the upper limit on the amplitude below the theoretical spin-down limit. The lowest upper limit on the amplitude is 6.4 × 10−27 for the young energetic pulsar J0537−6910, while the lowest constraint on the ellipticity is 8.8 × 10−9 for the bright nearby millisecond pulsar J0437−4715. Additionally, for a subset of 16 targets, we performed a narrowband search that is more robust regarding the emission model, with no evidence of a signal. We also found no evidence of nonstandard polarizations as predicted by the Brans─Dicke theory.

Keywords: Neutron stars, LIGO, Gravitational waves, Pulsars
Cosmic Filament Spin. II. Filament Spin and Its Impact on Galaxy Spin–Filament Alignment in a Cosmological Simulation. Observational studies have reported that cosmic filaments on the megaparsec scale exhibit rotational motion. Subsequent simulation studies have shown qualitative agreement with these findings, but quantitative discrepancies remain due to differences in data and methods, which require verification. To address this issue, we adopt the same methodology as used in the observations to identify filament spin from the galaxy distribution constructed from a hydrodynamic simulation. Using the same approach to measure filament spin, we find that the simulation results closely match the observational findings, with only minor discrepancies arising from slight differences in the fraction of filaments classified as dynamically cold or hot based on their dynamic temperature. Additionally, an analysis of how filament spin affects the galaxy spin–filament correlation shows that dynamically cold filaments with strong spin signals have a greater impact on the galaxy spin–filament correlation than those with weaker spin signals and dynamically hot filaments. These results not only provide further evidence that cosmic filaments exhibit spin but also highlight the importance of this rotation in the acquisition of angular momentum by individual galaxies. Future studies exploring the influence of filament spin on galaxy spin may shed light on the physical origins of filaments and the angular momentum of galaxies.

Keywords: Galaxy environments, Cosmic web, Astrostatistics, Large-scale structure of the universe
A Multiwavelength Autopsy of the Interacting Type IIn Supernova 2020ywx: Tracing Its Progenitor Mass-loss History for 100 Yr Before Death. While the subclass of interacting supernovae (SNe) with narrow hydrogen emission lines (Type IIn supernovae (SNe IIn)) consists of some of the longest-lasting and brightest supernovae (SNe) ever discovered, their progenitors are still not well understood. Investigating SNe IIn as they emit across the electromagnetic spectrum is the most robust way to understand the progenitor evolution before the explosion. This work presents X-ray, optical, infrared, and radio observations of the strongly interacting Type IIn supernova, SN 2020ywx, covering a period &gt;1200 days after discovery. Through multiwavelength modeling, we find that the progenitor of 2020ywx was losing mass at ∼10‑2–10‑3 M⊙ yr‑1 for at least 100 yr pre-explosion using the circumstellar medium (CSM) speed of 120 km s‑1 measured from optical and near-infrared (NIR) spectra. Despite the similar magnitude of mass loss measured in different wavelength ranges, we find discrepancies between the X-ray and optical/radio-derived mass-loss evolution, which suggest asymmetries in the CSM. Furthermore, we find evidence for dust formation due to the combination of a growing blueshift in optical emission lines and NIR continuum emission which we fit with blackbodies at ∼1000 K. Based on the observed elevated mass loss over more than 100 yr and the configuration of the CSM inferred from the multiwavelength observations, we invoke binary interaction as the most plausible mechanism to explain the overall mass-loss evolution. SN 2020ywx is thus a case that may support the growing observational consensus that SNe IIn mass loss is explained by binary interaction.

Keywords: Type II supernovae, Stellar mass loss, Circumstellar matter, X-ray transient sources, Radio transient sources
Revealing the CME Impact on the Martian Nightside Ionosphere Based on MAVEN and Tianwen-1 Observations. Due to the absence of an Earth-like dipole magnetic field, the impact of coronal mass ejections (CMEs) on the Martian nightside ionosphere differs from that on Earth and is still not well understood. This study investigates the responses in the Martian nightside ionosphere to a CME event that occurred on 2022 August 30 using observations from Tianwen-1 and Mars Atmosphere and Volatile EvolutioN. The ion density in the upper Martian nightside ionosphere between 200 and 500 km decreases when two successive CMEs hit the induced Martian magnetosphere, with a brief density recovery between the two CMEs. This suggests that ion density in the Martian nightside ionosphere between 200 and 500 km decreases as the intensity of CMEs increases. The primary cause of the observed decrease in the nightside ion density is likely due to the enhanced magnetic field pressure above the Martian ionosphere during CMEs, which facilitates ion escape from the dayside ionosphere; this subsequently reduces the amount of ions transported to the nightside ionosphere, thereby leading to a decrease in ion density on nightside. Furthermore, hemispheric asymmetry is found in the ionospheric response, indicating that the crustal magnetic fields in the southern hemisphere may play a role in slowing down the reduction of ion density. This study expands the comprehensive description of the impact of a CME event on different regions of Mars and its underlying mechanisms.

Keywords: Mars, Planetary ionospheres, Solar coronal mass ejections
Linking Critical Heights in Solar Active Regions with 3D Coronal Mass Ejection Speeds: Insights from Automated and Manual Polarity Inversion Line Detection Methods. In a space weather context, the most geoeffective coronal mass ejections (CMEs) are fast CMEs from Earth-facing solar active regions. These CMEs are difficult to characterize in coronagraph data due to their high speed (fewer observations), faintness, Earthward orientation (halo CMEs), and disruptions from associated high-energy particle storms. Any diagnostic aiding in early CME speed identification is valuable. This study investigates whether the 3D speeds of 37 CMEs are correlated with the critical heights of their source regions, to test the hypothesis that if the critical height is located at a higher altitude in the corona, the weaker magnetic field environment will enable a faster CME to be produced. Critical heights near CME onset are calculated by identifying polarity inversion lines (PIL) in magnetogram data using automated and manual methods. 3D speeds are determined by fitting a Graduated Cylindrical Shell model to multiviewpoint coronagraph images. For the automated method, we find a high correlation of 71% ± 8% between CME speed and critical height, dropping to 48% ± 12% when using CME plane-of-sky speeds, on which most previous similar studies are based. An attempt to improve the critical height diagnostic through manual PIL selection yields a lower correlation of 58% ± 13%. The higher correlation from the automated method suggests that encompassing the full PIL structure is a better measure of the magnetic conditions that influence CME dynamics. Our results highlight the potential for critical height as a continuously computable diagnostic for forecasting the 3D speeds of Earth-directed CMEs.

Keywords: Solar active region magnetic fields, Space weather, Active sun, Solar physics, Solar corona, Solar coronal mass ejections, Solar magnetic fields