Sazuna/UAT_keywords huggingface dataset:
The Accretion History of AGN: A Newly Defined Population of Cold Quasars. Quasars are the most luminous of active galactic nuclei, and are perhaps responsible for quenching star formation in their hosts. The Stripe 82X catalog covers 31.3 deg2 of the Stripe 82 field, of which the 15.6 deg2 covered with XMM-Newton is also covered by Herschel/SPIRE. We have 2500 X-ray detected sources with multiwavelength counterparts, and 30% of these are unobscured quasars, with LX &gt; 1044 erg s-1 and MB &lt; -23. We define a new population of quasars that are unobscured, have X-ray luminosities in excess of 1044 erg s-1, have broad emission lines, and yet are also bright in the far-infrared, with a 250 μm flux density of S250 &gt; 30 mJy. We refer to these Herschel-detected, unobscured quasars as "cold quasars." A mere 4% (21) of the X-ray- and optically selected unobscured quasars in Stripe 82X are detected at 250 μm. These cold quasars lie at z ∼ 1-3, have LIR &gt; 1012 L⊙, and have star formation rates (SFRs) of ∼200-1400 M⊙ yr-1. Cold quasars are bluer in the mid-IR than the full quasar population, and 72% of our cold quasars have WISE W3 &lt; 11.5 [Vega], while only 19% of the full quasar sample meets this criteria. Crucially, cold quasars have on average ∼nine times as much star formation as the main sequence of star-forming galaxies at similar redshifts. Although dust-rich, unobscured quasars have occasionally been noted in the literature before, we argue that they should be considered as a separate class of quasars due to their high SFRs. This phase is likely short-lived, as the central engine and immense star formation consume the gas reservoir. Cold quasars are type-1 blue quasars that reside in starburst galaxies.

Keywords: Starburst galaxies, Quasars, Far infrared astronomy
Using the Mark Weighted Correlation Functions to Improve the Constraints on Cosmological Parameters. We used the mark weighted correlation functions (MCFs), W(s), to study the large-scale structure of the universe. We studied five types of MCFs with the weighting scheme ρα, where ρ is the local density, and α is taken as -1, -0.5, 0, 0.5, and 1. We found that different MCFs have very different amplitudes and scale dependence. Some of the MCFs exhibit distinctive peaks and valleys that do not exist in the standard correlation functions. Their locations are robust against the redshifts and the background geometry; however, it is unlikely that they can be used as "standard rulers" to probe the cosmic expansion history. Nonetheless, we find that these features may be used to probe parameters related with the structure formation history, such as the values of σ8 and the galaxy bias. Finally, after conducting a comprehensive analysis using the full shapes of the W(s)s and WΔs(μ)s, we found that combining different types of MCFs can significantly improve the cosmological parameter constraints. Compared with using only the standard correlation function, the combinations of MCFs with α = 0, 0.5, 1 and α = 0, -1, -0.5, 0.5, 1 can improve the constraints on Ωm and w by ≈30% and 50%, respectively. We find highly significant evidence that MCFs can improve cosmological parameter constraints.

Keywords: Cosmological parameters from large-scale structure, Large-scale structure of the universe
ALMA Observations of Young Eruptive Stars: Continuum Disk Sizes and Molecular Outflows. We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations of four young, eruptive star-disk systems at 0"4 resolution: two FUors (V582 Aur and V900 Mon), one EXor (UZ Tau E), and one source with an ambiguous FU/EXor classification (GM Cha). The disks around GM Cha, V900 Mon, and UZ Tau E are resolved. These observations increase the sample of FU/EXors observed at subarcsecond resolution by 15%. The disk sizes and masses of FU/EXors objects observed by ALMA so far suggest that FUor disks are more massive than Class 0/I disks in Orion and Class II disks in Lupus of similar size. EXor disks in contrast do not seem to be distinguishable from these two populations. We reach similar conclusions when comparing the FU/EXor sample to the Class I and Class II disks in Ophiuchus. FUor disks around binaries are host to more compact disks than those in single-star systems, similar to noneruptive young disks. We detect a wide-angle outflow around GM Cha in 12CO emission, wider than typical Class I objects and more similar to those found around some FUor objects. We use radiative transfer models to fit the continuum and line data of the well-studied disk around UZ Tau E. The line data are well described by a Keplerian disk, with no evidence of outflow activity (similar to other EXors). The detection of wide-angle outflows in FUors but not in EXors support the current picture in which FUors are more likely to represent an accretion burst in the protostellar phase (Class I), while EXors are smaller accretion events in the protoplanetary (Class II) phase.

Keywords: Stellar accretion disks, Star formation, Protoplanetary disks
On the Possibility of Detecting Helium D3 Line Polarization with Metis. Metis, the space coronagraph on board the Solar Orbiter, offers us new capabilities for studying eruptive prominences and coronal mass ejections (CMEs). Its two spectral channels, hydrogen Lα and visible light (VL), will provide for the first time coaligned and cotemporal images to study dynamics and plasma properties of CMEs. Moreover, with the VL channel (580-640 nm) we find an exciting possibility to detect the helium D3 line (587.73 nm) and its linear polarization. The aim of this study is to predict the diagnostic potential of this line regarding the CME thermal and magnetic structure. For a grid of models we first compute the intensity of the D3 line together with VL continuum intensity due to Thomson scattering on core electrons. We show that the Metis VL channel will detect a mixture of both, with predominance of the helium emission at intermediate temperatures between 30 and 50,000 K. Then we use the code HAZEL to compute the degree of linear polarization detectable in the VL channel. This is a mixture of D3 scattering polarization and continuum polarization. The former one is lowered in the presence of a magnetic field and the polarization axis is rotated (Hanle effect). Metis has the capability of measuring Q/I and U/I polarization degrees and we show their dependence on temperature and magnetic field. At T = 30,000 K we find a significant lowering of Q/I which is due to strongly enhanced D3 line emission, while depolarization at 10 G amounts roughly to 10%.

Keywords: Coronagraphic imaging, Solar prominences, Solar coronal mass ejections
Project AMIGA: The Circumgalactic Medium of Andromeda. Project AMIGA (Absorption Maps In the Gas of Andromeda) is a survey of the circumgalactic medium (CGM) of Andromeda (M31, ${R}_{\mathrm{vir}}$ ≃ 300 kpc) along 43 QSO sightlines at impact parameters 25 ≤ R ≤ 569 kpc (25 at R ≲ ${R}_{\mathrm{vir}}$). We use ultraviolet absorption measurements of Si II, Si III, Si IV, C II, and C IV from the Hubble Space Telescope/Cosmic Origins Spectrograph and O IV from the Far Ultraviolet Spectroscopic Explorer to provide an unparalleled look at how the physical conditions and metals are distributed in the CGM of M31. We find that Si III and O VI have a covering factor near unity for R ≲ 1.2 ${R}_{\mathrm{vir}}$ and ≲1.9 ${R}_{\mathrm{vir}}$, respectively, demonstrating that M31 has a very extended ∼104-105.5 K ionized CGM. The metal and baryon masses of the 104-105.5 K CGM gas within ${R}_{\mathrm{vir}}$ are ≳108 and ≳4 × 1010 (Z/0.3 Z⊙)-1 M⊙, respectively. There is not much azimuthal variation in the column densities or kinematics, but there is with R. The CGM gas at R ≲ 0.5 ${R}_{\mathrm{vir}}$ is more dynamic and has more complicated, multiphase structures than at larger radii, perhaps a result of more direct impact of galactic feedback in the inner regions of the CGM. Several absorbers are projected spatially and kinematically close to M31 dwarf satellites, but we show that those are unlikely to give rise to the observed absorption. Cosmological zoom simulations of ∼L* galaxies have O VI extending well beyond ${R}_{\mathrm{vir}}$ as observed for M31 but do not reproduce well the radial column density profiles of the lower ions. However, some similar trends are also observed, such as the lower ions showing a larger dispersion in column density and stronger dependence on R than higher ions. Based on our findings, it is likely that the Milky Way has a ∼104-105.5 K CGM as extended as for M31 and their CGM (especially the warm-hot gas probed by O VI) are overlapping. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: Local Group, Andromeda Galaxy, Quasar absorption line spectroscopy, Circumgalactic medium
Nondetection of the Gamma-Ray Burst X-Ray Emission Line: The Down-Comptonization Effect. The detection of the gamma-ray burst (GRB) X-ray emission line is important for studying GRB physics and constraining the GRB redshift. Since the line-like feature in the GRB X-ray spectrum was first reported in 1999, several works on line searching have been published over the past two decades. Even though some observations on the X-ray line-like feature were performed, its significance remains controversial to date. In this paper, we utilize the down-Comptonization mechanism and present the time evolution of the Fe Kα line emitted near the GRB central engine. The line intensity decreases with the evolution time, and the time evolution depends on the electron density and the electron temperature. In addition, the initial line with a larger broadening decreases less over time. For instance, when the emission line penetrates material with an electron density above 1012 cm-3 at 1 keV, it generally becomes insignificant enough after 100 s for it not to be detected . The line-like profile deviates from the Gaussian form, and it finally changes to be similar to a blackbody shape at the time of the thermal equilibrium between the line photons and the surrounding material.

Keywords: X-ray detectors, Gamma-ray bursts
Late-time Circumstellar Interaction of SN 2017eaw in NGC 6946. SN 2017eaw, the tenth supernova observed in NGC 6946, was a normal Type II-P supernova with an estimated 11-13 M⊙ red supergiant progenitor. Here we present nebular-phase spectra of SN 2017eaw at +545 and +900 days post-max, extending approximately 50-400 days past the epochs of previously published spectra. While the +545 day spectrum is similar to spectra taken between days +400 and +493, the +900 day spectrum shows dramatic changes both in spectral features and emission-line profiles. The Hα emission is flat-topped and boxlike with sharp blue and red profile velocities of ≃-8000 and +7500 km s-1. These late-time spectral changes indicate strong circumstellar interaction with a mass-loss shell, expelled ∼1700 yr before explosion. SN 2017eaw's +900 day spectrum is similar to those seen for SN 2004et and SN 2013ej observed 2-3 yr after explosion. We discuss the importance of late-time monitoring of bright SNe II-P and the nature of presupernova mass-loss events for SN II-P evolution.

Keywords: Type II supernovae, Ejecta, Circumstellar matter, Core-collapse supernovae
SCUBA2 High Redshift Bright Quasar Survey: Far-infrared Properties and Weak-line Features. We present a submillimeter continuum survey ("SCUBA2 High rEdshift bRight quasaR surveY," hereafter SHERRY) of 54 high-redshift quasars at 5.6 &lt; z &lt; 6.9 with quasar bolometric luminosities in the range of (0.2-5) × 1014 L☉, using the Submillimetre Common-User Bolometer Array-2 (SCUBA2) on the James Clerk Maxwell Telescope. About 30% (16/54) of the sources are detected with a typical 850 μm rms sensitivity of 1.2 mJy beam-1 (Sν,850 μm = 4-5 mJy, at &gt;3.5σ). The new SHERRY detections indicate far-infrared (FIR) luminosities of 3.5 × 1012 to 1.4 × 1013 L☉, implying extreme star formation rates of 90-1060 M☉ yr-1 in the quasar host galaxies. Compared with z = 2-5 samples, the FIR-luminous quasars (LFIR &gt; 1013 L☉) are rarer at z ∼ 6. The optical/near-infrared spectra of these objects show that 11% (6/54) of the sources have weak Lyα emission-line features, which may relate to different subphases of the central active galactic nuclei (AGNs). Our SCUBA2 survey confirms the trend reported in the literature that quasars with submillimeter detections tend to have weaker ultraviolet (UV) emission lines compared to quasars with nondetections. The connection between weak UV quasar line emission and bright dust continuum emission powered by massive star formation may suggest an early phase of AGN-galaxy evolution, in which the broad-line region is starting to develop slowly or is shielded from the central ionization source, and has unusual properties such as weak-line features or bright FIR emission.

Keywords: Quasars, Observational cosmology, Active galaxies, Submillimeter astronomy, High-redshift galaxies
Does GW190425 Require an Alternative Formation Pathway than a Fast-merging Channel?. The LIGO/Virgo Scientific Collaboration (LVC) recently announced the detection of a compact object binary merger, GW190425, with a total mass of ${3.4}_{-0.1}^{+0.3}$ M⊙ and individual component masses in the range of about 1.1-2.5 M⊙. If the constituent compact objects are neutron stars, then the total mass is five standard deviations higher than the mean of 2.66 ± 0.12 M⊙ for Galactic binary neutron stars. LVC suggests that the nondetection of such massive binary neutron star (BNS) systems in the Galaxy is due to a selection effect. However, we are unable to reconcile the inferred formation efficiency from the reported merger rate, ${{ \mathcal R }}_{\mathrm{GW}190425}={460}_{-390}^{+1050}$ yr-1 Gpc-3, with predictions from our own study for fast-merging BNS systems. Moreover, the comparable merger rates of GW190425 and GW170817 are possibly in tension with our results for two reasons: (i) more massive systems are expected to have lower formation rates, and (ii) fast-merging channels should constitute ≲10% of the total BNS systems if case BB unstable mass transfer is permitted to take place as a formation pathway. We argue that, to account for the high merger rate of GW190425 as a BNS system, (i) our understanding of NS formation in supernova explosions must be revisited, or (ii) more massive NSs must be preferentially born with either very weak or very high magnetic fields so that they would be undetectable in the radio surveys. Perhaps the detected massive NSs in NS-white dwarf binaries are our clues to the formation path of GW190425 systems.

Keywords: LIGO, Neutron stars, Binary stars, Common envelope binary stars
Hunting for Runaways from the Orion Nebula Cluster. We use Gaia DR2 to hunt for runaway stars from the Orion Nebula Cluster (ONC). We search a region extending 45° around the ONC and out to 1 kpc to find sources that have overlapped in angular position with the cluster in the last ∼10 Myr. We find ∼17,000 runaway/walkaway candidates that satisfy this 2D traceback condition. Most of these are expected to be contaminants, e.g., caused by Galactic streaming motions of stars at different distances. We thus examine six further tests to help identify real runaways, namely: (1) possessing young stellar object (YSO) colors and magnitudes based on Gaia optical photometry; (2) having IR excess consistent with YSOs based on 2MASS and Wide-field Infrared Survey Explorer photometry; (3) having a high degree of optical variability; (4) having closest approach distances well-constrained to within the cluster half-mass radius; (5) having ejection directions that avoid the main Galactic streaming contamination zone; and (6) having a required radial velocity (RV) for 3D overlap of reasonable magnitude (or, for the 7% of candidates with measured RVs, satisfying 3D traceback). Thirteen sources, not previously noted as Orion members, pass all these tests, while another twelve are similarly promising, except they are in the main Galactic streaming contamination zone. Among these 25 ejection candidates, ten with measured RVs pass the most restrictive 3D traceback condition. We present full lists of runaway/walkaway candidates, estimate the high-velocity population ejected from the ONC, and discuss its implications for cluster formation theories via comparison with numerical simulations.

Keywords: Stellar kinematics, Young star clusters, Stellar dynamics, Star formation, Astrometry, Runaway stars
Steady Wind-blown Cavities within Infalling Rotating Envelopes: Application to the Broad Velocity Component in Young Protostars. Wind-driven outflows are observed around a broad range of accreting objects throughout the universe, ranging from forming low-mass stars to supermassive black holes. We study the interaction between a central isotropic wind and an infalling, rotating envelope, which determines the steady-state cavity shape formed at their interface under the assumption of weak mixing. The shape of the resulting wind-blown cavity is elongated and self-similar, with a physical size determined by the ratio between wind ram pressure and envelope thermal pressure. We compute the growth of a warm turbulent mixing layer between the shocked wind and the deflected envelope, and calculate the resultant broad-line profile, under the assumption of a linear (Couette-type) velocity profile across the layer. We then test our model against the warm broad velocity component observed in CO J = 16-15 by Herschel/HIFI in the protostar Serpens-Main SMM1. Given independent observational constraints on the temperature and density of the dust envelope around SMM1, we find an excellent match to all its observed properties (line profile, momentum, temperature) and to the SMM1 outflow cavity width for a physically reasonable set of parameters: a ratio of wind to infall mass flux of ≃4%, a wind speed of vw ≃ 30 km s-1, an interstellar abundance of CO and H2, and a turbulent entrainment efficiency consistent with laboratory experiments. The inferred ratio of ejection to disk accretion rate, ≃6%-20%, is in agreement with current disk wind theories. Thus, the model provides a new framework to reconcile the modest outflow cavity widths in protostars with large observed flow velocities. Being self-similar, it is applicable over a broader range of astrophysical contexts as well.

Keywords: Accretion, Stellar-interstellar interactions, Stellar jets, Astrochemistry, Stellar winds, Protostars
Demographics of Triple Systems in Dense Star Clusters. Depending on the stellar type, more than 15% of stars in the field have at least two stellar companions. Hierarchical triple systems can be assembled dynamically in dense star clusters, as a result of few-body encounters among stars and/or compact remnants in the cluster core. In this paper, we present the demographics of stellar and compact-object triples formed via binary-binary encounters in the CMC Cluster Catalog, a suite of cluster simulations with present-day properties representative of the globular clusters (GCs) observed in the Milky Way. We show how the initial properties of the host cluster set the typical orbital parameters and formation times of the formed triples. We find that a cluster typically assembles hundreds of triples with at least one black hole (BH) in the inner binary, while only clusters with sufficiently small virial radii are efficient in producing triples with no BHs. We show that a typical GC is expected to host tens of triples with at least one luminous component at present. We discuss how the Lidov-Kozai mechanism can drive the inner binary of these dynamically formed triples to high eccentricities, whenever it takes place before the triple is dynamically reprocessed by encountering another cluster member. Some of these systems can reach sufficiently large eccentricities to form a variety of transients and merger products, such as blue stragglers, X-ray binaries, Type Ia supernovae, Thorne-Zytkow objects, and gravitational wave sources.

Keywords: Globular star clusters, Neutron stars, Galaxy clusters, Milky Way dynamics, Stellar mass black holes, Gravitational wave astronomy, Gravitational waves, Trinary stars, Blue straggler stars, Milky Way Galaxy, Astrophysical black holes, Star clusters
Magnetic Reconnection during the Post-impulsive Phase of a Long-duration Solar Flare: Bidirectional Outflows as a Cause of Microwave and X-Ray Bursts. Magnetic reconnection plays a crucial role in powering solar flares, production of energetic particles, and plasma heating. However, where the magnetic reconnections occur, how and where the released magnetic energy is transported, and how it is converted to other forms remain unclear. Here we report recurring bidirectional plasma outflows located within a large-scale plasma sheet observed in extreme-ultraviolet emission and scattered white light during the post-impulsive gradual phase of the X8.2 solar flare on 2017 September 10. Each of the bidirectional outflows originates in the plasma sheet from a discrete site, identified as a magnetic reconnection site. These reconnection sites reside at very low altitudes (&lt;180 Mm, or 0.26 R⊙) above the top of the flare arcade, a distance only &lt;3% of the total length of a plasma sheet that extends to at least 10 R⊙. Each arrival of sunward outflows at the loop-top region appears to coincide with an impulsive microwave and X-ray burst dominated by a hot source (10-20 MK) at the loop top and a nonthermal microwave burst located in the loop-leg region. We propose that the reconnection outflows transport the magnetic energy released at localized magnetic reconnection sites outward in the form of kinetic energy flux and/or electromagnetic Poynting flux. The sunward-directed energy flux induces particle acceleration and plasma heating in the post-flare arcades, observed as the hot and nonthermal flare emissions.

Keywords: Solar flares, Solar magnetic reconnection, Non-thermal radiation sources, Solar coronal mass ejections, Solar radio flares
Solar Flare Arcade Modeling: Bridging the Gap from 1D to 3D Simulations of Optically Thin Radiation. Solar flares are 3D phenomena, but modeling a flare in 3D, including many of the important processes in the chromosphere, is a computational challenge. Accurately modeling the chromosphere is important, even if the transition region and corona are the areas of interest, due to the flow of energy, mass, and radiation through the interconnected layers. We present a solar flare arcade model that aims to bridge the gap between 1D and 3D modeling. Our approach is limited to the synthesis of optically thin emission. Using observed active region loop structures in a 3D domain, we graft simulated 1D flare atmospheres onto each loop, synthesize the emission, and then project that emission onto the 2D observational plane. Emission from SDO/AIA, GOES/XRS, and IRIS/SG Fe XXI λ1354.1 was forward modeled. We analyze the temperatures, durations, mass flows, and line widths associated with the flare, finding qualitative agreement but certain quantitative differences. Compared to observations, the Doppler shifts are of similar magnitude but decay too quickly. They are not as ordered, containing a larger amount of scatter compared to observations. The duration of gradual phase emission from GOES and AIA emission is also too short. Fe XXI lines are broadened, but not sufficiently. These findings suggest that additional physics is required in our model. The arcade model that we show here as a proof of concept can be extended to investigate other lines and global aspects of solar flares, providing a means to better test the coronal response to models of flare energy injection.

Keywords: Hydrodynamical simulations, Solar flares, Solar ultraviolet emission, Radiative transfer simulations, Solar flare spectra, Solar radiation, Solar x-ray flares, Active solar corona