Sazuna/UAT_keywords huggingface dataset:
Dying of the Light: An X-Ray Fading Cold Quasar at z ∼ 0.405. Cold quasars are a rare subpopulation observed to host unobscured, X-ray luminous active galactic nuclei (AGN) while also retaining a cold gas supply fueling high star formation rates. These objects are interpreted as AGN early in their evolution. We present new SOFIA HAWC+ far-infrared observations, far-ultraviolet to far-infrared (FUV-FIR) photometry, and optical spectroscopy to characterize the accretion and star formation behavior in a cold quasar at z ∼ 0.405 (CQ 4479). CQ 4479 is a starburst galaxy with a predominantly young stellar population and a high gas mass fraction of ∼50%-70%. The AGN component has yet to become the dominant component of the FIR emission. We also find AGN bolometric luminosity that varies as a function of observation method and AGN region probed. Finally, we identify a candidate outflow feature corroborating the hypothesis that cold quasars have energetic feedback. This object presents an intriguing look into the early stages of AGN feedback and probes the rare phase where an AGN and cold gaseous component coexist.

Keywords: Infrared excess galaxies, Active galactic nuclei, Galaxy evolution, X-ray quasars, Galaxy quenching
An Analysis of Soft X-Ray Structures at Kiloparsec Distances from the Active Nucleus of Centaurus A Galaxy. Here we reanalyze the archival Chandra data for the central parts of the Centaurus A radio galaxy, aiming for a systematic investigation of the X-ray emission associated with the inner radio lobes in the system, and their immediate surroundings. In particular, we focus on four distinct features characterized by the soft excess with respect to the adjacent fields. Those include the two regions located at kiloparsec distances from the nucleus to the west and east, the extended bow-shock structure to the south, and a fragment of a thin arc north of the center. The selected north, west, and south features coincide with the edges of the radio lobes, while the east structure is seemingly displaced from the radio-emitting plasma. Our X-ray spectral analysis reveals (i) a power-law emission component with photon index Γ ∼ 2 in the north, east, and south regions, and (ii) a dense (number density ∼0.3 cm-3) and relatively cold (temperature ∼ 0.2 keV) gas in the east and west regions. The power-law emission is consistent with the synchrotron continuum generated at the edges of the radio structure, and implies that the efficiency of the electron acceleration at the terminal bow shock does not vary dramatically over the inner lobes' extension. The presence of gaseous condensations, on the other hand, could possibly be understood in terms of a massive outflow from the central regions of the galaxy.

Keywords: X-ray astronomy, High energy astrophysics, Active galaxies, Non-thermal radiation sources, X-ray active galactic nuclei, X-ray sources
Spatially Resolved Study of Recombining Plasma in W49B Using XMM-Newton. W49B is the youngest supernova remnant (SNR) to date that exhibits recombining plasma. The two prevailing theories of this overionization are rapid cooling via adiabatic expansion or through thermal conduction with an adjacent cooler medium. To constrain the origin of the recombining plasma in W49B, we perform a spatially resolved spectroscopic study of deep XMM-Newton data across 46 regions. We adopt a three-component model (with one interstellar medium and two ejecta components), and we find that recombining plasma is present throughout the entire SNR, with increasing overionization from east to west. The latter result is consistent with previous studies, and we attribute the overionization in the west to adiabatic expansion. However, our findings depart from these prior works, as we find evidence of overionization in the east as well. As the SNR is interacting with molecular material there, we investigate the plausibility of thermal conduction as the origin of the rapid cooling. Based on estimated timescales, we show that both large- and small-scale thermal conduction can explain the observed overionization of the hotter ejecta. However, overionization of the cooler ejecta is only possible through small-scale thermal conduction resulting in evaporation of embedded, dense clouds with sizes ≲1 pc.

Keywords: X-ray astronomy, Radiative recombination, Dense interstellar clouds, Supernova remnants, Interstellar medium
Chandra Imaging of the Western Hotspot in the Radio Galaxy Pictor A: Image Deconvolution and Variability Analysis. Here we present an analysis of the X-ray morphology and flux variability of the particularly bright and extended western hotspot in the nearest powerful (FR II-type) radio galaxy, Pictor A, based on data obtained with the Chandra X-ray Observatory. The hotspot marks the position where the relativistic jet, which originates in the active nucleus of the system, interacts with the intergalactic medium, at hundreds-of-kiloparsec distances from the host galaxy, forming a termination shock that converts jet bulk kinetic energy to internal energy of the plasma. The hotspot is bright in X-rays due to the synchrotron emission of electrons accelerated to ultrarelativistic energies at the shock front. In our analysis, we make use of several Chandra observations targeting the hotspot over the last decades with various exposures and off-axis angles. For each pointing, we study in detail the point-spread function, which allows us to perform the image deconvolution, and to resolve the hotspot structure. In particular, the brightest segment of the X-ray hotspot is observed to be extended in the direction perpendicular to the jet, forming a thin, ∼3 kpc long, feature that we identify with the front of the reverse shock. The position of this feature agrees well with the position of the optical intensity peak of the hotspot, but is clearly offset from the position of the radio intensity peak, located ∼1 kpc further downstream. In addition, we measure the net count rate on the deconvolved images, finding a gradual flux decrease by about 30% over the 15 yr timescale of the monitoring.

Keywords: X-ray photometry, Relativistic jets, Active galaxies, Radio galaxies, Non-thermal radiation sources, X-ray quasars, X-ray sources, Shocks, Cosmic rays
Mysterious Globular Cluster System of the Peculiar Massive Galaxy M85. We present a study on the stellar population and kinematics of globular clusters (GCs) in the peculiar galaxy M85. We obtain optical spectra of 89 GCs at 8 kpc &lt; R &lt; 160 kpc using the MMT/Hectospec. We divide them into three groups, blue/green/red GCs (B/G/RGCs), with their (g - i)0 colors. All GC subpopulations have mean ages of about 10 Gyr, but showing differences in metallicities. The BGCs and RGCs are the most metal-poor ([Z/H] ∼ -1.49) and metal-rich ([Z/H] ∼ -0.45), respectively, and the GGCs are in between. We find that the inner GC system exhibits a strong overall rotation that is entirely due to a disklike rotation of the RGC system. The BGC system shows little rotation. The GGCs show kinematic properties clearly distinct among the GC subpopulations, having higher mean velocities than the BGCs and RGCs and being aligned along the major axis of M85. This implies that the GGCs have an origin different from the other GC subpopulations. The rotation-corrected velocity dispersion of the RGC system is much lower than that of the BGC system, indicating the truncation of the red halo of M85. The BGCs have a flat velocity dispersion profile out to R = 67 kpc, reflecting the dark matter extent of M85. Using the velocity dispersion of the BGC system, we estimate the dynamical mass of M85 to be 3.8 × 1012 M⊙. We infer that M85 has undergone merging events lately, resulting in the peculiar kinematics of the GC system.

Keywords: Lenticular galaxies, Elliptical galaxies, Virgo Cluster, Globular star clusters
HCN J = 4-3, HNC J = 1-0, H<SUP>13</SUP>CN J = 1-0, and HC<SUB>3</SUB>N J = 10-9 Maps of Galactic Center Region. II. Physical Properties of Dense-gas Clumps and Probability of Star Formation. We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN J = 4-3 map, whose optically thin critical density ( $\sim {10}^{7}\,{\mathrm{cm}}^{-3}$ ) is the highest among the tracers ever used in CMZ surveys. Logistic regression is performed to empirically formulate star formation probability of 195 HCN clumps, 13 of which contain star formation signatures. The explanatory parameters in the best-fit model are reduced into the virial parameter ${\alpha }_{\mathrm{vir}}$ without significant contribution from other parameters, whereas the performance of the model without ${\alpha }_{\mathrm{vir}}$ is no better than that using randomly generated data. The threshold ${\alpha }_{\mathrm{vir}}$ is 6, which translates into a volume density ( ${n}_{{{\rm{H}}}_{2}}$ ) of ${10}^{4.6}\,{\mathrm{cm}}^{-3}$ with the ${n}_{{{\rm{H}}}_{2}}$ - ${\alpha }_{\mathrm{vir}}$ correlation. The scarcity of the low- ${\alpha }_{\mathrm{vir}}$ clumps, whose fraction to all HCN clumps is 0.1, can be considered as one of the immediate causes of the suppressed SFE. No correlation between the clump size or mass and star formation probability is found, implying that HCN J = 4-3 does not immediately trace the mass of star-forming gas above a threshold density. Meanwhile, star-forming and non-star-forming clouds are degenerate in the physical parameters of the CS $J$ = 1-0 clouds, highlighting the efficacy of the HCN $J$ = 4-3 line to probe star-forming regions in the CMZ. The timescale of the high- ${\alpha }_{\mathrm{vir}}$ to low- ${\alpha }_{\mathrm{vir}}$ transition is $\lesssim 2\,\mathrm{Myr}$ , which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.

Keywords: Galactic center, Star formation, Molecular clouds
The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-epoch Spectroscopy. It is well known that reverberation mapping of active galactic nuclei (AGNs) reveals a relationship between AGN luminosity and the size of the broad-line region, and that use of this relationship, combined with the Doppler width of the broad emission line, enables an estimate of the mass of the black hole at the center of the active nucleus based on a single spectrum. An unresolved key issue is the choice of parameter used to characterize the line width, either FWHM or line dispersion ${\sigma }_{\mathrm{line}}$ (the square root of the second moment of the line profile). We argue here that use of FWHM introduces a bias, stretching the mass scale such that high masses are overestimated and low masses are underestimated. Here we investigate estimation of black hole masses in AGNs based on individual or "single-epoch" observations, with a particular emphasis in comparing mass estimates based on line dispersion and FWHM. We confirm the recent findings that, in addition to luminosity and line width, a third parameter is required to obtain accurate masses, and that parameter seems to be Eddington ratio. We present simplified empirical formulae for estimating black hole masses from the Hβ λ4861 and C IV λ1549 emission lines. While the AGN continuum luminosity at 5100 Å is usually used to predict the Hβ reverberation lag, we show that the luminosity of the Hβ broad component can be used instead without any loss of precision, thus eliminating the difficulty of accurately accounting for the host-galaxy contribution to the observed luminosity.

Keywords: Supermassive black holes, Active galactic nuclei, Quasars
Clumping in the Winds of Wolf-Rayet Stars. We attempt to determine the driver for clumping in hot-star winds by extending the measure of the spectral variability level of Galactic Wolf-Rayet stars to by far the hottest known among them, the WN2 star WR 2 and the WO2 stars WR 102 and WR 142. These three stars have T⋆ = 140 and 200 kK, the last two being well above the bulk of WR stars with T⋆ ∼ 40-120 kK. This full temperature range for WR stars is much broader than that of their O-star progenitors (∼30-50 kK), so is better suited to look for any temperature dependence of wind clumping. We have obtained multiple observations with high signal-to-noise, moderate-resolution spectroscopy in search of small-scale variability in the strong emission lines from the dense winds of these three extreme stars, and find a very low-level of variability in both stars. Temperature and terminal velocity are correlated, so faster winds show a lower variability, though this trend goes against any predictions made involving Line Deshadowing Instability (LDI) only, implying that instabilities intrinsic to LDI are not the main source of wind clumping. Instead, it could be taken as support for the suggestion that clumps are caused by a subsurface convection zone (SSCZ) at T ∼ 170 kK, since such an SSCZ would have little opportunity to operate under the hydrostatic surface of these hottest WR stars. It is still possible, however, that an SSCZ-related driver could interact with nonlinear line instability effects to enhance or possibly even produce clumps.

Keywords: Wolf-Rayet stars, Stellar winds, Radiative transfer, Stellar convective zones
Oumuamuas Passing through Molecular Clouds. The detections of 1I/'Oumuamua and 2I/Borisov within just two years of each other impressively demonstrate that interstellar objects (ISOs) must be common in the Milky Way. Once released from their parent system, these ISOs travel for billions of years through interstellar space. While often imagined as empty, interstellar space contains gas and dust most prominent in the form of molecular clouds. Performing numerical simulations, we test how often ISOs cross such molecular clouds (MCs). We find that the ISOs pass through MCs amazingly often. In the solar neighborhood, ISOs typically spend 0.1%-0.2% of their journey inside MCs, for relatively slow ISOs (&lt;5 km s-1) this can increase to 1%-2%, equivalent to 10-20 Myr per Gyr. Thus the dynamically youngest ISOs spend the longest time in MCs. In other words, MCs must mainly contain relatively young ISOs (&lt;1-2 Gyr). Thus the half-life of the seeding process by ISOs is substantially shorter than a stellar lifetime. The actual amount of time spent in MCs decreases with distance to the Galactic center. We find that ISOs pass through MCs so often that backtracing their path to find their parent star beyond 250 Myr seems pointless. Besides, we give a first estimate of the ISO density depending on the distance to the Galactic center based on the stellar distribution.

Keywords: Giant molecular clouds, Free floating planets, Oort cloud objects
Machine-learning Approach to Identification of Coronal Holes in Solar Disk Images and Synoptic Maps. Identification of solar coronal holes (CHs) provides information both for operational space weather forecasting and long-term investigation of solar activity. Source data for the first problem are typically from the most recent solar disk observations, while for the second problem it is convenient to consider solar synoptic maps. Motivated by the idea that the concept of CHs should be similar for both cases we investigate universal models that can learn CH segmentation in disk images and reproduce the same segmentation in synoptic maps. We demonstrate that convolutional neural networks trained on daily disk images provide an accurate CH segmentation in synoptic maps and their pole-centric projections. Using this approach we construct a catalog of synoptic maps for the period of 2010-20 based on SDO/AIA observations in the 193 Å wavelength. The obtained CH synoptic maps are compared with magnetic synoptic maps in the time-latitude and time-longitude diagrams. The initial results demonstrate that while in some cases the CHs are associated with magnetic flux-transport events there are other mechanisms contributing to the CH formation and evolution. To stimulate further investigations the catalog of synoptic maps is published in open access.

Keywords: Solar coronal holes, Astronomy data analysis, Solar magnetic fields
Caltech-NRAO Stripe 82 Survey (CNSS). III. The First Radio-discovered Tidal Disruption Event, CNSS J0019+00. We present the discovery of a nuclear transient with the Caltech-NRAO Stripe 82 Survey (CNSS), a dedicated radio transient survey carried out with the Karl G. Jansky Very Large Array (VLA). This transient, CNSS J001947.3+003527, exhibited a turn-on over a timescale of ≲1 yr, increasing in flux density at 3 GHz from &lt;0.14 mJy in 2014 February to 4.4 ± 0.1 mJy in 2015 March, reaching a peak luminosity of $5\times {10}^{28}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{Hz}}^{-1}$ around 2015 October. The association of CNSS J0019+00 with the nucleus (Gaia and our very-long baseline interferometry positions are consistent to within 1 pc) of a nearby S0 Seyfert galaxy at 77 Mpc, together with the radio spectral evolution, implies that this transient is most likely a tidal disruption event (TDE). Our equipartition analysis indicates the presence of a ∼15,000 km s-1 outflow, having energy ∼1049 erg. We derive the radial density profile for the circumnuclear material in the host galaxy to be proportional to R-2.5. All of these properties suggest resemblance with radio-detected thermal TDEs like ASASSN-14li and XMMSL1 J0740-85. No significant X-ray or optical emission is detected from CNSS J0019+00, although this may simply be due to the thermal emission being weak during our late-time follow-up observations. From the CNSS survey we have obtained the first unbiased measurement of the rate of radio TDEs, R(&gt;500μJy) of about 2 × 10-3 deg-2, or equivalently a volumetric rate of about 10 Gpc-3 yr-1. This rate implies that all-sky radio surveys such as the VLA Sky Survey and those planned with ASKAP, will find many tens of radio TDEs over the next few years.

Keywords: Tidal disruption, Radio interferometry, Radio transient sources
A Stochastic Theory of the Hierarchical Clustering. I. Halo Mass Function. We present a new theory for the hierarchical clustering of dark matter (DM) halos, based on stochastic differential equations, that constitutes a change of perspective with respect to existing frameworks (e.g., the excursion set approach); this work is specifically focused on the halo mass function. First, we present a stochastic differential equation that describes fluctuations in the mass growth of DM halos, as driven by a multiplicative white (Gaussian) noise dependent on the spherical collapse threshold and on the power spectrum of DM perturbations. We demonstrate that such a noise yields an average drift of the halo population toward larger masses, that quantitatively renders the standard hierarchical clustering. Then, we solve the Fokker-Planck equation associated to the stochastic dynamics, and obtain the Press &amp; Schechter mass function as a (stationary) solution. Moreover, generalizing our treatment to a mass-dependent collapse threshold, we obtain an exact analytic solution capable of fitting remarkably well the N-body mass function over a wide range in mass and redshift. All in all, the new perspective offered by the theory presented here can contribute to a better understanding of the gravitational dynamics leading to the formation, evolution, and statistics of DM halos across cosmic times.

Keywords: Cosmology, Dark matter
Intercycle and Intracycle Variation of Halo CME Rate Obtained from SOHO/LASCO Observations. We report on the properties of halo coronal mass ejections (HCMEs) in solar cycles 23 and 24. We compare the HCME properties between the corresponding phases (rise, maximum, and declining) in cycles 23 and 24 and compare those between the whole cycles. Despite the significant decline in the sunspot number (SSN) in cycle 24, which dropped by 46% with respect to cycle 23, the abundance of HCMEs is similar in the two cycles. The HCME rate per SSN is 44% higher in cycle 24. In the maximum phase, cycle 24 rate normalized to SSN increased by 127%, while the SSN dropped by 43%. The source longitudes of cycle 24 HCMEs are more uniformly distributed than those in cycle 23. We found that the average sky-plane speed in cycle 23 is ∼16% higher than that in cycle 24. The size distributions of the associated flares between the two cycles and the corresponding phases are similar. The average speed at a central meridian distance (CMD) ≥ 600 for cycle 23 is ∼28% higher than that of cycle 24. We discuss the unusual bump in HCME activity in the declining phase of cycle 23 as being due to exceptional active regions that produced many CMEs during 2003 October-2005 October. The differing HCME properties in the two cycles can be attributed to the anomalous expansion of cycle 24 CMEs. Considering the HCMEs in the rise, maximum, and declining phases, we find that the maximum phase shows the highest contrast between the two cycles.

Keywords: Solar cycle, Solar flares, Heliosphere, Sunspots, Active sun, Solar coronal mass ejections, Solar x-ray flares
The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). II. Molecular Outflows in the Extreme Early Stages of Protocluster Formation. We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA Survey of 70 μm dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6-70 μm dark prestellar clump candidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-three outflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rate of 14%. We discover six episodic molecular outflows associated with low- to high-mass cores, indicating that episodic outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range of core masses. The time span between consecutive ejection events is much smaller than those found in more evolved stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer accretion timescales than less massive cores. The lower accretion rates in these 70 μm dark objects compared to the more evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller than the turbulent energy dissipation rate, which suggests that outflow-induced turbulence cannot sustain the internal clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 μm dark clumps that is unrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars, or other motions.

Keywords: Interstellar line emission, Infrared dark clouds, Massive stars, Stellar jets, Protoclusters, Stellar winds, Star formation, Interstellar medium, Protostars