Sazuna/UAT_keywords huggingface dataset:
The Tidal Torque Theory Revisited. I. Protohalo Angular Momentum. In tidal torque theory, the angular momentum (AM) of dark matter halos arises from the tidal torque suffered by aspherical collapsing patches due to surrounding mass fluctuations. This theory was implemented in the peak model, where protohalos are ellipsoidal. However, the adopted delimitations of these objects were doubtful and the protohalo AM was calculated numerically, which complicated the interpretation of the result and compromised its applicability. In addition, the AM of the final halos was derived without taking into account nonlinear effects. Here, we rederive the protohalo AM in the peak model, delimiting ellipsoids in the usual natural way and following a novel fully analytic approach that leads to a very simple and practical expression. The predicted AM is shown to fully agree with the results of cosmological simulations. In the following Paper II, we will apply this model to infer the rotational properties of relaxed halos, accounting for shell crossing and major mergers.

Keywords: Cosmology, Galaxy dark matter halos, Hierarchical cosmology, Dark matter
Highly Variable Quasar Candidates Selected from 4XMM-DR13 with Machine Learning. We present a sample of 12 quasar candidates with highly variable soft X-ray emission, selected from the fourth XMM-Newton Serendipitous Source Catalog (4XMM-DR13), using random forest (RF). Optical to mid-IR photometric data for the 4XMM-DR13 sources were obtained by correlating the sample with the Sloan Digital Sky Survey (SDSS) DR18 photometric catalog and the AllWISE database. By further cross matching with known spectral catalogs from the SDSS and LAMOST surveys, we compiled a training data set containing stars, galaxies, and quasars. The RF algorithm was trained to classify the XMM–Wide-field Infrared Survey Explorer–SDSS sample. We then refined the quasar candidate selection by applying Gaia proper motion data to eliminate stellar contaminants. As a result, 52,486 quasar candidates were classified, with 8410 of them matching known quasars in SIMBAD. The quasar candidates exhibit systematically lower X-ray fluxes compared to quasars in the training set, suggesting that the classifier is effective in identifying fainter quasars. From this quasar candidate sample, we constructed a subset of 12 sources that have shown variations in their soft X-ray flux by a factor of 10 over ∼20 yr in the XMM-Newton survey. These highly variable quasar candidates extend the quasar sample characterized by extreme soft X-ray variability to the optically faint end, with magnitudes around r ∼ 22. Notably, none of these 12 sources were detected in ROSAT observations. Given the flux sensitivity of ROSAT, the result indicates that quasars exhibiting more than 2 orders of magnitude of variation are extremely rare.

Keywords: X-ray quasars, Quasars
Unveiling the Cosmic Chemistry. II. "Direct" T<SUB>e</SUB>-based Metallicity of Galaxies at 3 &lt; z &lt; 10 with JWST/NIRSpec. We report the detection of the [O III] auroral line in 42 galaxies within the redshift range of 3 &lt; z &lt; 10. These galaxies were selected from publicly available JWST data releases, including the JADES and PRIMAL surveys, and observed using both the low-resolution PRISM/CLEAR configuration and medium-resolution gratings. The measured electron temperatures in the high-ionization regions of these galaxies range from Te([O III]) = 12,000 to 24,000 K, consistent with temperatures observed in local metal-poor galaxies and previous JWST studies. In 10 galaxies, we also detect the [O II] auroral line, allowing us to determine electron temperatures in the low-ionization regions, which range between Te([O II]) = 10,830 and 20,000 K. The direct Te-based metallicities of our sample span from 12 + log(O/H) = 7.2 to 8.4, indicating these high-redshift galaxies are relatively metal-poor. By combining our sample with 25 galaxies from the literature, we expand the data set to a total of 67 galaxies within 3 &lt; z &lt; 10, effectively more than doubling the previous sample size for direct Te-based metallicity studies. This larger data set allows us to derive empirical metallicity calibration relations based exclusively on high-redshift galaxies, using six key line ratios: R3, R2, R23, Ne3O2, O32, and O3N2. Notably, we derive a novel metallicity calibration relation for the first time using high-redshift Te-based metallicities:   = 0.18log R2 + 0.98log R3. This new calibration significantly reduces the scatter in high-redshift galaxies compared to the   relation previously calibrated for low-redshift galaxies.

Keywords: High-redshift galaxies
Using Machine Learning to Estimate Near-ultraviolet Magnitudes and Probe Quenching Mechanisms of z = 0 Nuggets in the RESOLVE and ECO Surveys. We present a z = 0 census of nuggets—compact galaxies that form via gas-rich violent disk instability—within the luminosity- and volume-limited RESOLVED Spectroscopy Of a Local VolumE (RESOLVE) and Environmental COntext (ECO) surveys. We use random forest (RF) models to predict near-ultraviolet (NUV) magnitudes for ECO galaxies that lack high-quality NUV magnitudes, thereby doubling the number of ECO galaxies with reliable extinction-corrected star formation rates (SFRs) and red/green/blue classifications based on specific SFRs (sSFRs). The resulting RF-enhanced RESOLVE+ECO nugget sample allows us to analyze rare subpopulations—green nuggets and nuggets with active galactic nuclei (AGN)—likely associated with quenching. Green nuggets are more similar to red nuggets than to blue nuggets in halo mass (Mhalo) distribution, with both red and green nuggets being found mainly at Mhalo ≥ 1011.4M⊙, where permanent halo quenching is predicted. At these masses, the AGN frequency for green nuggets is higher (48.2% ) than for either blue (39.2% ) or red (29.3% ) nuggets. Between Mhalo = 1011.4–1012M⊙, at the onset of permanent quenching, the AGN frequency for green nuggets is nearly double the frequency for blue or red nuggets, implying AGN are associated with this transition. At Mhalo &lt; 1011.4M⊙, where temporary cyclic quenching is expected, the AGN frequency for blue nuggets (7.5% ) is lower than for either green (31.3% ) or red (18.8% ) nuggets. At all masses, nuggets with AGN have reduced sSFRs and likely also atomic gas content compared to nuggets without AGN, but the quenching is more extreme below Mhalo = 1011.4M⊙.

Keywords: Blue compact dwarf galaxies, Galaxy bulges, Compact dwarf galaxies, Active galactic nuclei, Galaxy evolution, Galaxy quenching, Random Forests, Early-type galaxies
Stellar Variability toward the Galactic Open Cluster NGC 7209. We present the analysis of stellar variability in an open cluster NGC 7209 using optical V-band CCD photometric observations. Out of 4499 stars in our study, we detected 284 candidate variables, including one identified previously. Using the machine learning algorithm HDBSCAN technique and Gaia DR3 data, we identified 246 cluster members with membership probability greater than 60%, among which 17 were identified in our study as variable stars. Based on isochrone fitting, we approximated the log(age) of the cluster to be 8.8 ± 0.2. We provide the first time-series V-band photometric study of 14 newly detected variable cluster members, detecting three potential δ Scuti, three γ Doradus, and four rotationally modulated variables, along with four possible eclipsing binaries. We detected an optical flare on 2022 November 30, from the star ID 1329 (R.A.: 331.50897; decl.: 46.44859), with an estimated emitted energy of 5.37 × 1030 erg, which is below the typical energy range of a superflare; an error of a few tens of percent is attributed to the calculation of energy.

Keywords: Delta Scuti variable stars, Flare stars, Astrometric binary stars, Variable stars, Open star clusters, Gamma Doradus variable stars
Comparison of Plasma Dynamics in Coronal Holes and Quiet Sun Using Flux Emergence Simulations. This paper presents a comparison of plasma dynamics in coronal holes (CHs) and quiet Sun (QS) through 2.5D MHD flux emergence simulations. The magnetic reconnection between the emerging and the preexisting flux leads to the formation of cool, dense plasmoids with hot boundaries, and hot and cool jets with velocities ≈50 km s‑1. We perform a spectral synthesis in spectral lines probing transition region and coronal temperatures. CHs show reduced intensities, excess upflows (downflows), and widths during the jetting (downflow) period when compared to QS. During the jetting and downflow periods, the velocity and line width of the hot spectral lines in CHs show a strong positive correlation with the vertical magnetic field at z = 0, while the intensity of the cooler lines shows a weak correlation, which is not seen in QS. During the jetting period in CH, we find upflows in Si IV to be correlated (anticorrelated) with upflows (downflows) in other lines, and downflows in CH in Si IV to be correlated (anticorrelated) with upflows (downflows) in other lines when compared to QS. During the downflow, we find no strong correlation between Si IV and other line velocities. The correlation during the jetting period occurs due to coincident, cospatial origins of the hot and cool jet, while the lack of correlation during the downflow phase suggests a decoupling of hot and cool plasma. These results demonstrate that flux emergence and reconnection with preexisting flux in the atmosphere support a unified scenario for solar wind formation and coronal heating.

Keywords: Magnetohydrodynamics, Solar magnetic flux emergence, Solar magnetic reconnection, Plasma jets, Solar coronal heating, Solar wind, Solar magnetic fields, Solar transition region, Solar coronal holes
Revisiting the Intergalactic Medium around GRB 130606A and Constraints on the Epoch of Reionization. Gamma-ray bursts (GRBs) are excellent probes of the high-redshift Universe due to their high luminosities and the relatively simple intrinsic spectra of their afterglows. They can be used to estimate the fraction of neutral hydrogen (i.e., the neutral fraction) in the intergalactic medium (IGM) at different redshifts through the examination of their Lyα damping wing with high-quality optical-to-near-infrared spectra. Neutral fraction estimates can help trace the evolution of the Epoch of Reionization (EoR), a key era of cosmological history in which the IGM underwent a phase change from neutral to ionized. We revisit GRB 130606A, a z ∼ 5.9 GRB for which multiple analyses, using the same damping-wing model and data from different telescopes, found conflicting neutral fraction results. We identify the source of the discrepant results to be differences in assumptions for key damping-wing model parameters and data range selections. We perform a new analysis implementing multiple GRB damping-wing models and find a 3σ neutral fraction upper limit ranging from   to  . We present this result in the context of other neutral fraction estimates and EoR models, discuss the impact of relying on individual GRB lines of sight, and highlight the need for more high-redshift GRBs to effectively constrain the progression of the EoR.

Keywords: Reionization, Gamma-ray bursts, Infrared spectroscopy, Intergalactic medium
Statistical Analysis of Compact Single-source Flares Observed by STIX. X-ray emissions from solar flares provide a comprehensive overview of the spatial and spectral behaviors of high-temperature plasma in the solar atmosphere. In particular, compact flares are one of the best candidates for quantifying the geometrical properties of the X-ray source, which is crucial in the estimation of flare energetics. Accordingly, we present a statistical investigation of 550 flares showing one compact source in images reconstructed with the MARLIN, Expectation Maximization, and Forward Fit algorithms in the 6–10 keV soft X-ray (SXR) energy channel of the Spectrometer Telescope for Imaging X-rays (STIX), on board Solar Orbiter. We compare various properties of the sources, reconstructed with the aforesaid algorithms, which show consistency. We further test different approaches to estimating source sizes. We find better agreement between the tested algorithms using the 50% signal contour for size estimation instead of the commonly used 50% isophote. Thermal–nonthermal flare plasma parameters and energetics are investigated for a subset of flares exhibiting significant enhancement in the 12–20 keV hard X-ray (HXR) energy channel. While strong correlations are found between the emitted SXR and HXR flux with temperature, the HXR flux with nonthermal energy, and thermal with nonthermal energy, plasma parameters were not significantly correlated with the flare size or volume. The thermal–nonthermal emission partition during compact flares, characterized using the Neupert effect, is revealed only for 40% of events. We find the fraction of HXR fluence to SXR flux to be positively correlated with volume while moderately anticorrelated with density. This indicates that tenuous flare loops emit relatively less SXR emission as a response to deposited energy, compared to dense loops.

Keywords: Solar activity, Solar flares
The Size of the Continuum Emission Region and Its Scaling Relations with Active Galactic Nucleus Luminosity and the Broad-line Region Size. We present a continuum lag analysis for a sample of 37 relatively high-luminosity active galactic nuclei (AGNs) from the Seoul National University AGN Monitoring Project (SAMP), utilizing the light-curve data in B and V bands from SAMP and in g, r, i bands from the Zwicky Transient Facility. We find that the interband lags (τ) increase with the wavelength (i.e., τ ∝ λ∼4/3) as prescribed by the standard disk model (Shakura–Sunyaev disk, hereafter SSD), suggesting consistency with the "lamp-post" reprocessing model. We report that the size of the continuum emitting region (CER) normalized at 2500 Å (R2500) is a factor of ∼5 (i.e., 0.69 ± 0.04 dex) larger than predicted by SSD. By combining our new measurements with the remeasurements of the literature sample, we report a correlation between R2500 and AGN continuum luminosity as  , which suggests that the observed continuum could be composed of both the disk emission and the diffuse emission from the broad-line region (BLR). The size of CER shows a tight relation with the size of Hβ BLR with a sublinear slope (i.e.,  ) and a scatter of 0.29 dex. This empirical relation offers a promising method for estimating single-epoch black hole masses, once established over a large dynamic range of AGN luminosity.

Keywords: Reverberation mapping, Active galactic nuclei, Black holes, Quasars
A Classification Scheme for Quasar Absorption Lines. We present a method to classify intergalactic absorption lines and apply it to 10,772 low-redshift systems. The classification gives the number of components (reflecting the kinematics) in four different ionization phases, using detections and nondetections of H I, high (O VI, N V, O V, Ne V, Ne VI, Ne VIII), medium (C III, Si III, O III, O IV, C IV) and low (C II, N II, O II, Si II, He I) ions. In this manner, we unify the "Lyα forest," "O VI absorbers," "C IV absorbers," "Mg II absorbers," etc. We identify three main absorber types: systems without metals (type A, 86.8% of the sample), systems with high- and/or medium-ionization ions only (type B, 10.2%), and systems with low-ionization lines (type C, 3.0%). Type A mostly has single-component systems (82.2%), type B has 43.2% single-component systems, while type C absorbers mostly have multiple hydrogen components (20.6% are single). The fraction of systems with a given number of components is basically independent of the signal-to-noise ratio. Our scheme describes the observed data for each system and can be used to define samples of similar absorbers. From absorbers with available galaxy information, we find that type A systems occur both near to and far from galaxies, type C systems trace the denser circumgalactic medium (CGM) and group gas, while type B systems trace the tenuous CGM and intergalactic medium. We present new determinations of dn/dz for the 58 most common intergalactic absorption lines. We show that a rest-frame velocity of 3000 km s‑1 relative to the active galactic nucleus is preferred for separating intergalactic from associated absorbers.

Keywords: Quasar absorption line spectroscopy, Intergalactic medium
The Structure, Populations, and Kinematics of the Milky Way Central and Inner Bulge with OGLE, APOGEE, and Gaia Data. We present an analysis of the structure, kinematics, and chemo-dynamical properties of the Milky Way bulge using RR Lyrae stars from Optical Gravitational Lensing Experiment (OGLE), and giant stars from APOGEE and Gaia that have distances placing them in the inner Galaxy. First, using a sample of 1879 ab-type RR Lyrae stars (RRabs) from OGLE-IV, we identified three populations: central bulge RRabs, the inner bulge RRabs, and halo or disk interlopers, based on their apocenters derived from orbital integration. Inner bulge RRabs kinematically align with the Galactic bar, while central bulge RRabs show slower rotation with lower velocity dispersion. Higher velocity dispersion stars were identified as halo/disk interlopers. Then, an orbital analysis of 28,188 APOGEE Red Clump and Red Giant Branch stars revealed kinematic properties consistent with RRabs, and the chemical abundance distribution displayed a bimodal stellar density pattern, suggesting complex star evolution histories and slightly different star formation histories for the inner bulge and central bulge. The differences in the density distribution on the ∣Z∣max-eccentricity plane for the central bulge, inner bulge, and interlopers are clearly detected. It is found that the classification of bulge stars based on orbital parameters, rather than solely on metallicity, provides a more accurate population separation. As the inner bulge, which contains the highest fraction of stars, traces the bar formed by the instability of the Galactic disk, our results support that the pseudobulge is the primary origin of the bulge. Furthermore, fitting the observed data to both the boxy and X-shaped bulge models indicated a preference for the boxy bulge.

Keywords: Milky Way Galaxy physics, Milky Way disk, Galactic bulge
A 50 s Quasiperiodic Oscillation in the Early X-Ray Afterglow of GRB 220711B. It is generally believed that long-duration gamma-ray bursts (GRBs) originate from the core collapse of rapidly spinning massive stars, and at least some of them are powered by hyperaccreting black holes (BHs). However, definite proofs about the progenitor and central engine of these GRBs have not been directly observed in the past. Here, we report the existence of a quasiperiodic oscillation (QPO) signature with periodic frequency ∼0.02 Hz in the early X-ray afterglow phase of GRB 220711B. Such a low-frequency QPO likely signals the precession of a relativistic jet launched from a GRB hyperaccreting BH central engine. The energy injection signature from the late X-ray observations (from 5 × 102 s ∼ 1 × 104 s) is consistent with the precession hypothesis. The prompt gamma-ray light curve does not show any QPO signature, suggesting that the X-ray flaring emission in the early afterglow phase and prompt emission likely originate from different accretion processess, indicating that the progenitor stars of GRBs have a core-envelope structure with a stratified angular momentum distribution and the late-time accretion disk likely has a misalignment with respect to the rotation axis of the BH. Such a misalignment is not expected in a canonical collapsar model. As a result, the QPO signature in GRB 220711B may reveal a new formation channel of long GRBs, possibly a stellar-merger-induced core collapse, with the orbital angular momentum of the binary misaligned with the spin axis of the collapsing star.

Keywords: Gamma-ray bursts
First Measurements of Black Hole Accretion and Radio-jet Timescales in a Young Quasar at the Edge of Reionization. We present the first study dedicated to measuring the timescales for black hole accretion and jet launching in a quasar at the edge of reionization, PSO J352.4034─15.3373 at z = 5.832 ± 0.001. Previous work presented evidence of the strong radio synchrotron emission from the jet affecting the host galaxy's dust-dominated continuum emission at νrest = 683 GHz (νobs = 100 GHz), implying a break in the synchrotron spectrum. In this work, we present quasi-simultaneous observations at 1.5 GHz─42 GHz with the Karl G. Jansky Very Large Array, and derive a frequency break at   GHz (  GHz). Modeling these observations, we calculate the jet spectral aging from the cooling of electrons to be tspec ∼ 580 yr. From this measurement, we approximate the dynamical age tdyn to be ∼2000 yr, implying a recent jet ejection. We compare the jet timescale to the quasar's lifetime (tQ) that indicates the duration of the latest black hole accretion event and is derived from the proximity zone size in the rest-UV/optical spectrum. However, a ghostly damped Lyα system affects this measurement yielding an upper limit of tQ ≲ 104 yr, consistent with the jet lifetime and indicative of a young quasar. This suggests that the triggering of a UV-bright quasar phase may occur within comparable timescales as the launch of a relativistic radio jet. Therefore, we may be witnessing an early stage of black hole and jet interactions in a quasar during the first billion years of the Universe.

Keywords: Accretion, Supermassive black holes, Radio jets, Quasars, Radio loud quasars
Effects of Metallicity on Graphite, TiC, and SiC Condensation in Carbon Stars. From transmission electron microscopy and other laboratory studies of presolar grains, the implicit condensation sequence of carbon-bearing condensates in circumstellar envelopes of carbon stars is (from first to last) TiC-graphite-SiC. We use thermochemical equilibrium condensation calculations and show that the condensation sequence of titanium carbide (TiC), graphite (C(Gr)), and silicon carbide (SiC) depends on metallicity in addition to C/O ratio and total pressure. Calculations were performed for a characteristic carbon star ratio of C/O = 1.2 from 10‑10 to 10‑4 bars total pressure and for uniform metallicity variations ranging from 0.01 to 100 times solar elemental abundances. TiC always condenses at higher temperatures than SiC, and the carbide condensation temperatures increase with both increasing metallicity and increasing total pressure. Graphite, however, can condense in a cooling circumstellar envelope before TiC, between TiC and SiC, or after SiC, depending on the carbon-bearing gas chemistry, which is dependent on metallicity and total pressure. Analytical expressions for the graphite, TiC, and SiC condensation temperatures as functions of metallicity and total pressure are presented. The inferred sequence from laboratory presolar grain studies, TiC-graphite-SiC, is favored under equilibrium conditions at solar and subsolar metallicities between ∼10‑5 and 10‑8 bar total pressure within circumstellar envelopes of carbon stars with nominal C/O = 1.2. We also explored the dependence of the sequence at C/O ratios of 1.1 and 3.0, and found that as the C/O ratio increases, the TiC-graphite-SiC condensation sequence region occurs toward higher total pressures and lower metallicities.

Keywords: Carbon stars, Asymptotic giant branch stars, Carbonaceous grains, Circumstellar grains, Circumstellar dust, Chemical thermodynamics