Sazuna/UAT_keywords huggingface dataset:
A Comprehensive Study on the Variation Phenomena of AO 0235+164. The variation mechanism of blazars is a long-standing open question. Observations of polarization can provide us with more information to constrain models. In this work, we collect long-term multiwavelength data on AO 0235+164, and analyse the correlations between them by using the local cross-correlation function. We find that both γ-ray and the optical V-band light curves are correlated with the radio light curve beyond the 3σ significance level. The regions emitting the γ-ray and optical radiation coincide within errors, and are located ${6.6}_{-1.7}^{+0.6}$ pc upstream of the core region of 15 GHz, which is beyond the broad-line region. The color index shows the redder-when-brighter trend in the low flux state, but turns to the bluer-when-brighter trend in the high flux state, while the γ-ray spectral index always shows the softer-when-brighter trend. We propose that such complex variation trends can be explained by the increasing jet component with two constant components. The optical polarization degree (PD) flares and optical flux flares are not synchronous. It seems that one flux peak is sandwiched by two PD peaks, which have inverse rotation trajectories in the qu plane. The helical jet model can schematically show these characteristics of polarization with fine-tuned parameters. The change in viewing angle is suggested to be the primary variable that leads to all these variations, although other possibilities such as the shock-in-jet model or the hadronic model are not excluded completely.

Keywords: Blazars, Relativistic jets, Active galactic nuclei, Radio jets
Spectroscopic Monitoring of Blazar S5 0716+714: Brightness-dependent Spectral Behavior. In this paper, we report new results of spectroscopic observations of γ-ray blazar S5 0716+714 from 2019 September to 2020 March with the 2.4 m optical telescope at Lijiang Observatory of Yunnan Observatories. The median cadence of observations is ∼1 day. During the second observation period (Epoch2), the observational data reveal an extremely bright state and a bluer-when-brighter (BWB) chromatism. The BWB trend of Epoch2 differs significantly from that of the first observation period (Epoch1). A significantly brightness-dependent BWB chromatism emerges in the total data of Epoch1 and Epoch2. The BWB trend becomes weaker toward the brighter states, and likely becomes saturated at the highest state. Based on a log-parabolic function, a power law of synchrotron peak flux and frequency νp, and a power law of the curvature of synchrotron spectrum and its νp, simulation well reproduces the brightness-dependent BWB trend of S5 0716+714. The BWB trend is seemingly controlled by the shift of νp with respect to the observational window, and effectively may be dominated by the variations of electron average energy and magnetic field in the emitting region.

Keywords: BL Lacertae objects, Blazars, Relativistic jets, Active galactic nuclei, Spectroscopy
The Magnetic Field of the Active Planet-hosting M Dwarf AU Mic. AU Mic is a young, very active M dwarf star with a debris disk and at least one transiting Neptune-size planet. Here we present a detailed analysis of the magnetic field of AU Mic based on previously unpublished high-resolution optical and near-infrared spectropolarimetric observations. We report a systematic detection of circular and linear polarization signatures in the stellar photospheric lines. Tentative Zeeman Doppler imaging modeling of the former data suggests a nonaxisymmetric global field with a surface-averaged strength of about 90 G. At the same time, linear polarization observations indicate the presence of a much stronger ≍2 kG axisymmetric dipolar field, which contributes no circular polarization signal due to the equator-on orientation of AU Mic. A separate Zeeman broadening and intensification analysis allowed us to determine a mean field modulus of 2.3 and 2.1 kG from the Y- and K-band atomic lines, respectively. These magnetic field measurements are essential for understanding environmental conditions within the AU Mic planetary system.

Keywords: M dwarf stars, Stellar magnetic fields, Stellar activity
Efficient Mass Estimate at the Core of Strong Lensing Galaxy Clusters Using the Einstein Radius. In the era of large surveys, yielding thousands of galaxy clusters, efficient mass proxies at all scales are necessary in order to fully utilize clusters as cosmological probes. At the cores of strong lensing clusters, the Einstein radius can be turned into a mass estimate. This efficient method has been routinely used in literature, in lieu of detailed mass models; however, its scatter, assumed to be $\sim 30 \% $ , has not yet been quantified. Here, we assess this method by testing it against ray-traced images of cluster-scale halos from the Outer Rim N-body cosmological simulation. We measure a scatter of 13.9% and a positive bias of 8.8% in $M(\lt {\theta }_{{\rm{E}}})$ , with no systematic correlation with total cluster mass, concentration, or lens or source redshifts. We find that increased deviation from spherical symmetry increases the scatter; conversely, where the lens produces arcs that cover a large fraction of its Einstein circle, both the scatter and the bias decrease. While spectroscopic redshifts of the lensed sources are critical for accurate magnifications and time delays, we show that for the purpose of estimating the total enclosed mass, the scatter introduced by source redshift uncertainty is negligible compared to other sources of error. Finally, we derive and apply an empirical correction that eliminates the bias, and reduces the scatter to 10.1% without introducing new correlations with mass, redshifts, or concentration. Our analysis provides the first quantitative assessment of the uncertainties in $M(\lt {\theta }_{{\rm{E}}})$ , and enables its effective use as a core mass estimator of strong lensing galaxy clusters.

Keywords: Galaxy clusters, Strong gravitational lensing, Dark matter
Hyper Suprime-Cam Low Surface Brightness Galaxies. II. A Hubble Space Telescope Study of the Globular Cluster Systems of Ultradiffuse Galaxies in Groups. We increase the sample of ultradiffuse galaxies (UDGs) in lower-density environments with characterized globular cluster (GC) populations using new Hubble Space Telescope observations of nine UDGs in group environments. While the bulk of our UDGs have GC abundances consistent with normal dwarf galaxies, two of these UDGs have excess GC populations. These two UDGs both have GC luminosity functions consistent with higher surface brightness galaxies and cluster UDGs. We then combine our nine objects with previous studies to create a catalog of UDGs with analyzed GC populations that spans a uniquely diverse range of environments. We use this catalog to examine broader trends in the GC populations of low stellar mass galaxies. The highest GC abundances are found in cluster UDGs, but whether cluster UDGs are actually more extreme requires the study of many more UDGs in groups. We find a possible positive correlation between GC abundance and stellar mass, and between GC abundance and galaxy size at fixed stellar mass. However, we see no significant relation between stellar mass and galaxy size, over our limited stellar mass range. We consider possible origins of the correlation between GC abundance and galaxy size, including the possibility that these two galaxy properties are both dependent on the galaxy dark matter halo, or that they are related through baryonic processes like internal feedback. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-15277.

Keywords: Globular star clusters, Galaxy formation, Galaxy evolution
ZTF Early Observations of Type Ia Supernovae. II. First Light, the Initial Rise, and Time to Reach Maximum Brightness. While it is clear that Type Ia supernovae (SNe) are the result of thermonuclear explosions in C/O white dwarfs (WDs), a great deal remains uncertain about the binary companion that facilitates the explosive disruption of the WD. Here, we present a comprehensive analysis of a large, unique data set of 127 SNe Ia with exquisite coverage by the Zwicky Transient Facility (ZTF). High-cadence (six observations per night) ZTF observations allow us to measure the SN rise time and examine its initial evolution. We develop a Bayesian framework to model the early rise as a power law in time, which enables the inclusion of priors in our model. For a volume-limited subset of normal SNe Ia, we find that the mean power-law index is consistent with 2 in the rZTF-band ( ${\alpha }_{r}=2.01\pm 0.02$ ), as expected in the expanding fireball model. There are, however, individual SNe that are clearly inconsistent with ${\alpha }_{r}=2$ . We estimate a mean rise time of 18.9 days (with a range extending from ∼15 to 22 days), though this is subject to the adopted prior. We identify an important, previously unknown, bias whereby the rise times for higher-redshift SNe within a flux-limited survey are systematically underestimated. This effect can be partially alleviated if the power-law index is fixed to α = 2, in which case we estimate a mean rise time of 21.7 days (with a range from ∼18 to 23 days). The sample includes a handful of rare and peculiar SNe Ia. Finally, we conclude with a discussion of lessons learned from the ZTF sample that can eventually be applied to observations from the Vera C. Rubin Observatory.

Keywords: Observational astronomy, Surveys, Type Ia supernovae, Supernovae, Catalogs
ZTF Early Observations of Type Ia Supernovae. III. Early-time Colors As a Test for Explosion Models and Multiple Populations. Colors of Type Ia supernovae (SNe Ia) in the first few days after explosion provide a potential discriminant between different models. In this paper, we present g - r colors of 65 SNe Ia discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that g - r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties ( ${\sigma }_{\mathrm{noise}}\sim {\sigma }_{\mathrm{int}}\,\sim $ 0.18 mag). Colors are nearly constant starting from 6 days after first light (g - r ∼ -0.15 mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of ∼-0.25 mag day-1) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of 56Ni mixed in the outermost regions of the ejecta and with "double-detonation" models having thin helium layers ( ${M}_{\mathrm{He}}=0.01\,{M}_{\odot }$ ) and varying carbon-oxygen core masses. At the same time, six events show evidence for a distinctive "red bump" signature predicted by double-detonation models with larger helium masses. We finally identify a significant correlation between the early-time g - r slopes and supernova brightness, with brighter events associated to flatter color evolution (p-value = 0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on B - V colors.

Keywords: Surveys, Type Ia supernovae, Supernovae
Revisiting the Complex Nuclear Region of NGC 6240 with Chandra. We present a reanalysis of the cumulative ACIS-S Chandra data set pointed at the double active galactic nuclei (AGNs) of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I Kα line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used the full Chandra telescope angular resolution and modeled the Chandra point-spread function (PSF) by comparing a preflight calibration model to the data for the two bright AGNs. With two complementary approaches—(1) studying the residuals after PSF subtraction and (2) producing reconstructed Expectation through Markov Chain Monte Carlo (EMC2) images—we are able to resolve structures extending from ∼1 kpc to &lt;200 pc in the S AGN. The latter are within the sphere of influence of this BH. We find significant extended emission in both continuum and Fe lines in the ∼2″ (∼1 kpc) region surrounding the nuclei, in the region between the N and S AGN, and in a sector of PA 120-210 deg. extending to the SE from the centroid of the S AGN surface brightness. The extended Fe I Kα emission is likely to originate from the fluorescence of X-ray photons interacting with dense molecular clouds, providing a complementary view to recent high-resolution Atacama Large Millimeter/submillimeter Array (ALMA) studies. The nonthermal emission is more prevalent in the region in between the two active X-ray nuclei and in the N AGN. We do not find strong evidence of X-ray emission associated with the third nucleus recently proposed for NGC 6240.

Keywords: X-ray active galactic nuclei
Local Simulations of Heating Torques on a Luminous Body in an Accretion Disk. A luminous body embedded in an accretion disk can generate asymmetric density perturbations that lead to a net torque and thus orbital migration of the body. Linear theory has shown that this heating torque gives rise to a migration term linear in the body's mass that can oppose or even reverse that arising from the sum of gravitational Lindblad and co-orbital torques. We use high-resolution local three-dimensional shearing sheet simulations of a zero-mass test particle in an unstratified disk to assess the accuracy and domain of applicability of the linear theory. We find agreement between analytic and simulation results to better than 10% in the low-luminosity, low thermal conductivity regime but measure deviations in both the nonlinear (high-luminosity) and high thermal conductivity regimes. In the nonlinear regime, linear theory overpredicts the acceleration due to the heating torque, potentially due to the neglect of nonlinear terms in the heat flux. In the high thermal conductivity regime, linear theory underpredicts the acceleration, which scales with a power-law index of -1 rather than -3/2, although here both nonlinear and computational constraints play a role. We discuss the impact of the heating torque for the evolution of low-mass planets in protoplanetary disks and massive stars or accreting compact objects embedded in active galactic nucleus disks. For the latter case, we show that the thermal torque is likely to be the dominant physical effect at disk radii where the optical depth drops below $\tau \lesssim 0.07{\alpha }^{-3/2}\epsilon c/{v}_{K}$ .

Keywords: Hydrodynamical simulations, Galaxy accretion disks, Active galactic nuclei, Protoplanetary disks, Planet formation
Elemental Abundances in M31: Properties of the Inner Stellar Halo. We present measurements of [Fe/H] and [α/Fe] for 128 individual red giant branch stars (RGB) in the stellar halo of M31, including its Giant Stellar Stream (GSS), obtained using spectral synthesis of low- and medium-resolution Keck/DEIMOS spectroscopy ( $R\sim 3000$ and 6000, respectively). We observed four fields in M31's stellar halo (at projected radii of 9, 18, 23, and 31 kpc), as well as two fields in the GSS (at 33 kpc). In combination with existing literature measurements, we have increased the sample size of [Fe/H] and [α/Fe] measurements from 101 to a total of 229 individual M31 RGB stars. From this sample, we investigate the chemical abundance properties of M31's inner halo, finding $\langle [\mathrm{Fe}/{\rm{H}}]\rangle =-1.08\pm 0.04$ and $\langle [\alpha /\mathrm{Fe}]\rangle =0.40\pm 0.03$ . Between 8 and 34 kpc, the inner halo has a steep [Fe/H] gradient (-0.025 ± 0.002 dex kpc-1) and negligible [α/Fe] gradient, where substructure in the inner halo is systematically more metal-rich than the smooth component of the halo at a given projected distance. Although the chemical abundances of the inner stellar halo are largely inconsistent with that of present-day dwarf spheroidal (dSph) satellite galaxies of M31, we identified 22 RGB stars kinematically associated with the smooth component of the stellar halo that have chemical abundance patterns similar to M31 dSphs. We discuss formation scenarios for M31's halo, concluding that these dSph-like stars may have been accreted from galaxies of similar stellar mass and star formation history, or of higher stellar mass and similar star formation efficiency. * The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: Galaxy formation, Stellar abundances, Galaxy stellar halos, Galaxy abundances, Andromeda Galaxy
Extracting the Possible Intrinsic Relation between the Radiative Efficiency and Mass of QSOs: A Maximum Likelihood Method and its Application to the SDSS DR7 QSOs. Radiative efficiencies of QSOs and their distribution encode rich information on the evolution of both masses and spins of massive black holes (MBHs) across cosmic time. In this paper, we develop a maximum likelihood method to statistically extract the intrinsic relation between radiative efficiency (ɛ) and mass (M•) of QSOs from their distribution on the luminosity-(empirically estimated virial) mass plane. By using mock samples, we find that strong constraint can be put on the ɛ-M• relation at redshift z ≲ 0.4 from uniform QSO samples similar to those in the Sloan Digital Sky Survey (SDSS) and from QSO samples at z ∼ 0.6 (or ≲1.0) if the magnitude limit of the survey can be ∼1-2 (or 2-3) magnitude deeper. Applying this method to the SDSS DR7 QSOs with z ≲ 0.7, we find $\epsilon \propto {M}_{\bullet }^{0\sim 1.1}$ (or $\epsilon \propto {M}_{\bullet }^{-1.0\sim 0}$ ) correlation for QSOs with the masses obtained according to the H β (or Mg II) empirical mass estimator. These contradictory results may be due to the unknown systematic errors in the two mass estimators, preventing an accurate constraint on the ɛ-M• relation by using current available QSO samples. We find that both the estimates of MBH mass and Eddington ratio distribution functions can be affected by the ɛ- ${M}_{\bullet }$ relation, suggesting that the determination of this relation is important for understanding the accretion and growth history of MBHs. In the future, the intrinsic ɛ-M• relation is expected to be strongly constrained by using QSO samples obtained from surveys deeper than the SDSS if the host galaxy contamination and systematic errors of the mass estimator(s) can be well modeled or removed.

Keywords: Accretion, Black hole physics, Supermassive black holes, Quasars, Galaxy accretion disks
ALMA CO Observations of Gamma-Ray Supernova Remnant N132D in the Large Magellanic Cloud: Possible Evidence for Shocked Molecular Clouds Illuminated by Cosmic-Ray Protons. N132D is the brightest gamma-ray supernova remnant (SNR) in the Large Magellanic Cloud (LMC). We carried out 12CO(J = 1-0, 3-2) observations toward the SNR using the Atacama Large Millimeter/submillimeter Array (ALMA) and Atacama Submillimeter Telescope Experiment. We find diffuse CO emission not only at the southern edge of the SNR as previously known, but also inside the X-ray shell. We spatially resolved nine molecular clouds using ALMA with an angular resolution of 5″, corresponding to a spatial resolution of ∼1 pc at the distance of the LMC. Typical cloud sizes and masses are ∼2.0 pc and ∼100 M⊙, respectively. High intensity ratios of CO J = 3-2/1-0 &gt; 1.5 are seen toward the molecular clouds, indicating that shock heating has occurred. Spatially resolved X-ray spectroscopy reveals that thermal X-rays in the center of N132D are produced not only behind a molecular cloud but also in front of it. Considering the absence of a thermal component associated with the forward shock toward one molecular cloud located along the line of sight to the center of the remnant, this suggests that this particular cloud is engulfed by shock waves and is positioned on the near side of the remnant. If the hadronic process is the dominant contributor to the gamma-ray emission, the shock-engulfed clouds play a role as targets for cosmic rays. We estimate the total energy of cosmic-ray protons accelerated in N132D to be ∼0.5-3.8 × 1049 erg as a conservative lower limit, which is similar to that observed in Galactic gamma-ray SNRs.

Keywords: Gamma-ray sources, Large Magellanic Cloud, Supernova remnants, Cosmic ray sources, X-ray sources, Interstellar medium
Mapping the Escape Fraction of Ionizing Photons Using Resolved Stars: A Much Higher Escape Fraction for NGC 4214. We demonstrate a new method for measuring the escape fraction of ionizing photons using Hubble Space Telescope imaging of resolved stars in NGC 4214, a local analog of high-redshift starburst galaxies that are thought to be responsible for cosmic reionization. Specifically, we forward model the UV through near-IR spectral energy distributions of ∼83,000 resolved stars to infer their individual ionizing flux outputs. We constrain the local escape fraction by comparing the number of ionizing photons produced by stars to the number that are either absorbed by dust or consumed by ionizing the surrounding neutral hydrogen in individual star-forming regions. We find substantial spatial variation in the escape fraction (0%-40%). Integrating over the entire galaxy yields a global escape fraction of ${25}_{-15}^{+16}$ %. This value is much higher than previous escape fractions of zero reported for this galaxy. We discuss the sources of this apparent tension and demonstrate that the viewing angle and 3D interstellar medium geometric effects are the cause. If we assume that NGC 4214 has no internal dust, like many high-redshift galaxies, we find an escape fraction of 59% (an upper limit for NGC 4214). This is the first nonzero escape fraction measurement for UV-faint (M ${}_{\mathrm{FUV}}$ = -15.9) galaxies at any redshift and supports the idea that starburst UV-faint dwarf galaxies can provide a sufficient number of ionizing photons to the intergalactic medium.

Keywords: Dwarf irregular galaxies, Galaxy formation, Star formation, Galaxy evolution, Interstellar medium, Reionization