Sazuna/UAT_keywords huggingface dataset:
Extended Radio AGN at z ∼ 1 in the ORELSE Survey: The Confining Effect of Dense Environments. Recent hydrodynamic simulations and observations of radio jets have shown that the surrounding environment has a large effect on their resulting morphology. To investigate this, we use a sample of 50 Extended Radio Active Galactic Nuclei (ERAGN) detected in the Observations of Redshift Evolution in Large-Scale Environments survey. These sources are all successfully cross-identified to galaxies within a redshift range of 0.55 ≤ z ≤ 1.35, either through spectroscopic redshifts or accurate photometric redshifts. We find that ERAGN are more compact in high-density environments than those in low-density environments at a significance level of 4.5σ. Among a series of internal properties under our scrutiny, only the radio power demonstrates a positive correlation with their spatial extent. After removing the possible radio power effect, the difference of size in low- and high-density environments persists. In the global environment analyses, the majority (86%) of high-density ERAGN reside in the cluster/group environment. In addition, ERAGN in the cluster/group central regions are preferentially compact with a small scatter in size, compared to those in the cluster/group intermediate regions and fields. In conclusion, our data appear to support the interpretation that the dense intracluster gas in the central regions of galaxy clusters plays a major role in confining the spatial extent of radio jets.

Keywords: Radio active galactic nuclei, Galaxy clusters, Radio galaxies, Radio jets
Dark Matter-Dark Energy Interaction and the Shape of Cosmic Voids. Interaction between dark matter (DM) and dark energy (DE) is one of the not completely solved problems in cosmology that has been studied extensively. This interaction affects cosmic structures. In this regard, the shape of cosmic voids can be influenced by the DM and DE interaction. Here, employing the dynamical DE model constrained by observational data, we study the effects of this interaction on the ellipticity of cosmic voids. With this aim, we apply the linear growth of density perturbation in the presence of interaction. The probability-density distribution for the ellipticity of cosmic voids is investigated. The results confirm that the ellipticity of cosmic voids increases when the DM and DE interaction is considered.

Keywords: Large-scale structure of the universe, Dark matter, Dark energy
Radiation Magnetohydrodynamic Simulations of Sub-Eddington Accretion Flows in AGNs: Origin of Soft X-Ray Excess and Rapid Time Variabilities. We investigate the origin of the soft X-ray excess component in Seyfert galaxies observed when their luminosity exceeds 0.1% of the Eddington luminosity ( ${L}_{\mathrm{Edd}}$ ). The evolution of a dense blob in radiatively inefficient accretion flow (RIAF) is simulated by applying a radiation magnetohydrodynamic code, CANS+R. When the accretion rate onto a ${10}^{7}\,{M}_{\odot }$ black hole exceeds 10% of the Eddington accretion rate ( ${\dot{M}}_{\mathrm{Edd}}={L}_{\mathrm{Edd}}/{c}^{2}$ , where c is the speed of light), the dense blob shrinks vertically because of radiative cooling and forms a Thomson thick, relatively cool (∼107-8 K) region. The cool region coexists with the optically thin, hot ( $T\sim {10}^{11}\,{\rm{K}}$ ) RIAF near the black hole. The cool disk is responsible for the soft X-ray emission, while hard X-rays are emitted from the hot inner accretion flow. Such a hybrid structure of hot and cool accretion flows is consistent with the observations of both hard and soft X-ray emissions from "changing-look" active galactic nuclei (CLAGNs). Furthermore, we find that quasi-periodic oscillations (QPOs) are excited in the soft X-ray-emitting region. These oscillations can be the origin of rapid X-ray time variabilities observed in CLAGNs.

Keywords: Radiative magnetohydrodynamics, Galaxy accretion disks, Active galactic nuclei
Interferometric Monitoring of Gamma-Ray Bright AGNs: OJ 287. We present the results of simultaneous multifrequency imaging observations at 22, 43, 86, and 129 GHz of OJ 287. We used the Korean Very Long Baseline Interferometry Network as part of the Interferometric Monitoring of Gamma-ray Bright active galactic nuclei (iMOGABA). The iMOGABA observations were performed during 31 epochs from 2013 January 16 to 2016 December 28. We also used 15 GHz OVRO and 225 GHz SMA flux density data. We analyzed four flux enhancements in the light curves. The estimated timescales of three flux enhancements were similar with timescales of ∼50 days at two frequencies. A fourth flux enhancement had a variability timescale approximately twice as long. We found that 225 GHz enhancements led the 15 GHz enhancements by a range of 7-30 days in the time delay analysis. We found the fractional variability did not change with frequency between 43 and 86 GHz. We could reliably measure the turnover frequency, ${\nu }_{{\rm{c}}}$ , of the core of the source in three epochs. This was measured to be in a range from 27 to 50 GHz and a flux density at the turnover frequency, ${S}_{{\rm{m}}}$ , ranging from 3 to 6 Jy. The derived SSA magnetic fields, ${B}_{\mathrm{SSA}}$ , are in a range from 0.157 ± 0.104 to 0.255 ± 0.146 mG. We estimated the equipartition magnetic field strengths to be in a range from 0.95 ± 0.15 to 1.93 ± 0.30 mG. The equipartition magnetic field strengths are up to a factor of 10 higher than the values of ${B}_{\mathrm{SSA}}$ . We conclude that the downstream jet may be more particle energy dominated.

Keywords: Active galactic nuclei, Very long baseline interferometry, BL Lacertae objects, Radio jets
A Search for Ultra-high-energy Neutrinos from TXS 0506+056 Using the Pierre Auger Observatory. Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, Fermi-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith-angle range from θ = 60° to θ = 95°, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: one of 6 months around the detection of IceCube-170922 A, coinciding with a flare period of TXS 0506+056, a second one of 110 days during which the IceCube collaboration found an excess of 13 neutrinos from a direction compatible with TXS 0506+056, and a third one from 2004 January 1 up to 2018 August 31, over which the Pierre Auger Observatory has been taking data. The sensitivity of the Observatory is addressed for different spectral indices by considering the fluxes that would induce a single expected event during the observation period. For indices compatible with those measured by the IceCube collaboration the expected number of neutrinos at the Observatory is well below one. Spectral indices as hard as 1.5 would have to apply in this energy range to expect a single event to have been detected.

Keywords: High energy astrophysics, Blazars, Neutrino astronomy, Active galaxies, Transient sources
The Elusive Distance Gradient in the Ultrafaint Dwarf Galaxy Hercules: A Combined Hubble Space Telescope and Gaia View. The ultrafaint dwarf galaxy Hercules has an extremely elongated morphology with both photometric overdensities and kinematic members at large radii, suggesting that it may be tidally disrupting due to a previous close encounter with the Milky Way. To explain its observational peculiarities, we present a deep Hubble Space Telescope (HST) imaging study of Hercules and its surrounding regions and investigate its tidal history through a careful search for a distance gradient along its stretched body. Our off-center HST data clearly resolve a main sequence, showing that the stellar extension seen along the major axis of Hercules is genuine, not a clump of background galaxies. Utilizing Gaia DR2 data, we clean the region around the Hercules of field contamination, and find four new plausible member stars, all of which are located on the outskirts of the dwarf galaxy. We update the distance to Hercules, and find 130.6 ± 6.1 kpc ( $m-M=20.58\pm 0.10$ ) for the main body, which is consistent with earlier estimates in the literature. While we find no conclusive evidence for a distance gradient, our work demonstrates that constraining a distance gradient in such a faint system is not trivial, and the possible thickness of the dwarf along the line of sight and field contamination make it harder to make decisive conclusions even with these high-precision data. Future studies coupled with tailored theoretical models are needed to understand the true nature of Hercules and of tidal distortion observables in ultrafaint galaxies in general.

Keywords: Local Group, Galaxy dynamics, Dwarf galaxies, Galaxy interactions, HST photometry, Galaxy kinematics, Proper motions
Assessing Spectroscopic Binary Multiplicity Properties Using Robo-AO Imaging. We present higher-order multiplicity results for 60 solar-type spectroscopic binaries based on 0.75 μm imaging data taken by the robotic adaptive optics (Robo-AO) system at the Kitt Peak 2.1 m telescope. Our contrast curves show sensitivity up to ∼5 mag at ∼1″ separation; at very small separations, we identify candidate companions from image deviations relative to the point spread function. We find candidate tertiary companions for 62% of our binaries overall, but we find that this fraction is a strong function of the inner binary orbital period; it ranges from ∼47% for Pbin &gt; 30 days to as high as ∼90% for Pbin ≲ 5 days. We similarly find an increasing tertiary companion frequency for shorter-period binaries in a secondary sample of Kepler eclipsing binaries observed by Robo-AO. Using Gaia distances, we estimate an upper limit orbital period for each tertiary candidate and compare the tertiary-to-binary period ratios for systems in the field versus those in star-forming regions. Taken all together, these results provide further evidence for angular momentum transfer from three-body interactions, resulting in tight binaries with tertiaries that widen from pre-main-sequence to field ages.

Keywords: Trinary stars, Binary stars, Dynamical evolution
High-energy Neutrino and Gamma-Ray Emission from Tidal Disruption Events. Tidal disruption events (TDE) have been considered as cosmic-ray and neutrino sources for a decade. We suggest two classes of new scenarios for high-energy multi-messenger emission from TDEs that do not have to harbor powerful jets. First, we investigate high-energy neutrino and gamma-ray production in the core region of a supermassive black hole. In particular, we show that ∼1-100 TeV neutrinos and MeV gamma rays can efficiently be produced in hot coronae around an accretion disk. We also study the consequences of particle acceleration in radiatively inefficient accretion flows (RIAFs). Second, we consider possible cosmic-ray acceleration by sub-relativistic disk-driven winds or interactions between tidal streams, and show that subsequent hadronuclear and photohadronic interactions inside the TDE debris lead to GeV-PeV neutrinos and sub-GeV cascade gamma rays. We demonstrate that these models should be accompanied by soft gamma rays or hard X-rays as well as optical/UV emission, which can be used for future observational tests. Although this work aims to present models of non-jetted high-energy emission, we discuss the implications of the TDE AT2019dsg that might coincide with the high-energy neutrino IceCube-191001A, by considering the corona, RIAF, hidden sub-relativistic wind, and hidden jet models. It is not yet possible to be conclusive about their physical association and the expected number of neutrinos is typically much less than unity. We find that the most optimistic cases of the corona and hidden wind models could be consistent with the observation of IceCube-191001A, whereas jet models are unlikely to explain the multi-messenger observations.

Keywords: Black holes, High energy astrophysics, High-energy cosmic radiation, Tidal disruption, Cosmological neutrinos, Gamma-ray transient sources, Particle astrophysics
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO Excitation and Atomic Carbon in Star-forming Galaxies at z = 1-3. We investigate the CO excitation and interstellar medium (ISM) conditions in a cold gas mass-selected sample of 22 star-forming galaxies at z = 0.46-3.60, observed as part of the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS). Combined with Very Large Array follow-up observations, we detect a total of 34 CO $J\to J-1$ transitions with J = 1 up to 8 (and an additional 21 upper limits, up to J = 10) and 6 $[{\rm{C}}\,{\rm\small{I}}]$ ${}^{3}{P}_{1}{\to }^{3}\,{P}_{0}$ and ${}^{3}{P}_{2}{\to }^{3}\,{P}_{1}$ transitions (and 12 upper limits). The CO(2-1) and CO(3-2)-selected galaxies, at $\langle z\rangle =1.2$ and 2.5, respectively, exhibit a range in excitation in their mid-J = 4, 5 and high-J = 7, 8 lines, on average lower than ( ${L}_{\mathrm{IR}}$ -brighter) BzK-color- and submillimeter-selected galaxies at similar redshifts. The former implies that a warm ISM component is not necessarily prevalent in gas mass-selected galaxies at $\langle z\rangle =1.2$ . We use stacking and Large Velocity Gradient models to measure and predict the average CO ladders at z &lt; 2 and z ≥ 2, finding ${r}_{21}=0.75\pm 0.11$ and ${r}_{31}=0.77\pm 0.14$ , respectively. From the models, we infer that the galaxies at z ≥ 2 have intrinsically higher excitation than those at z &lt; 2. This fits a picture in which the global excitation is driven by an increase in the star formation rate surface density of galaxies with redshift. We derive a neutral atomic carbon abundance of $(1.9\pm 0.4)\times {10}^{-5}$ , comparable to the Milky Way and main-sequence galaxies at similar redshifts, and fairly high densities (≥104 cm-3), consistent with the low-J CO excitation. Our results imply a decrease in the cosmic molecular gas mass density at z ≥ 2 compared to previous ASPECS measurements.

Keywords: Galaxy formation, Millimeter astronomy, Dust continuum emission, Galaxy evolution, Interstellar medium, CO line emission, High-redshift galaxies
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Multiband Constraints on Line-luminosity Functions and the Cosmic Density of Molecular Gas. We present a CO and atomic fine-structure line-luminosity function analysis using the ALMA Spectroscopic Survey (ASPECS) in the Hubble Ultra Deep Field. ASPECS consists of two spatially overlapping mosaics that cover the entire ALMA 3 mm and 1.2 mm bands. We combine the results of a line-candidate search of the 1.2 mm data cube with those previously obtained from the 3 mm cube. Our analysis shows that ∼80% of the line flux observed at 3 mm arises from CO(2-1) or CO(3-2) emitters at z = 1-3 ("cosmic noon"). At 1.2 mm, more than half of the line flux arises from intermediate-J CO transitions (Jup = 3-6); ∼12% from neutral carbon lines; and &lt;1% from singly ionized carbon, [C II]. This implies that future [C II] intensity mapping surveys in the epoch of reionization will need to account for a highly significant CO foreground. The CO luminosity functions probed at 1.2 mm show a decrease in the number density at a given line luminosity (in units of L') at increasing Jup and redshift. Comparisons between the CO luminosity functions for different CO transitions at a fixed redshift reveal subthermal conditions on average in galaxies up to z ∼ 4. In addition, the comparison of the CO luminosity functions for the same transition at different redshifts reveals that the evolution is not driven by excitation. The cosmic density of molecular gas in galaxies, ρH2, shows a redshift evolution with an increase from high redshift up to z ∼ 1.5 followed by a factor ∼6 drop down to the present day. This is in qualitative agreement with the evolution of the cosmic star formation rate density, suggesting that the molecular gas depletion time is approximately constant with redshift, after averaging over the star-forming galaxy population.

Keywords: Luminosity function, Molecular gas, Galaxy evolution
The Evolution of the Baryons Associated with Galaxies Averaged over Cosmic Time and Space. We combine the recent determination of the evolution of the cosmic density of molecular gas (H2) using deep, volumetric surveys, with previous estimates of the cosmic density of stellar mass, star formation rate and atomic gas (H I), to constrain the evolution of baryons associated with galaxies averaged over cosmic time and space. The cosmic H I and H2 densities are roughly equal at z ∼ 1.5. The H2 density then decreases by a factor ${6}_{-2}^{+3}$ to today's value, whereas the H I density stays approximately constant. The stellar mass density is increasing continuously with time and surpasses that of the total gas density (H I and H2) at redshift z ∼ 1.5. The growth in stellar mass cannot be accounted for by the decrease in cosmic H2 density, necessitating significant accretion of additional gas onto galaxies. With the new H2 constraints, we postulate and put observational constraints on a two-step gas accretion process: (i) a net infall of ionized gas from the intergalactic/circumgalactic medium to refuel the extended H I reservoirs, and (ii) a net inflow of H I and subsequent conversion to H2 in the galaxy centers. Both the infall and inflow rate densities have decreased by almost an order of magnitude since z ∼ 2. Assuming that the current trends continue, the cosmic molecular gas density will further decrease by about a factor of two over the next 5 Gyr, the stellar mass will increase by approximately 10%, and cosmic star formation activity will decline steadily toward zero, as the gas infall and accretion shut down.

Keywords: Molecular gas, High-redshift galaxies, Galaxy evolution, Interstellar medium
The ALMA Spectroscopic Survey Large Program: The Infrared Excess of z = 1.5-10 UV-selected Galaxies and the Implied High-redshift Star Formation History. We make use of sensitive (9.3 μJy beam-1 rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field (ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range z = 1.5-10 (to ∼7-28 M☉ yr-1 at 4σ over the entire range). We find that the fraction of ALMA-detected galaxies in our z = 1.5-10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 109.0 M☉ to ${85}_{-18}^{+9}$ % at &gt;1010 M☉. Moreover, on stacking all 1253 low-mass (&lt;109.25 M☉) galaxies over the ASPECS footprint, we find a mean continuum flux of -0.1 ± 0.4 μJy beam-1, implying a hard upper limit on the obscured star formation rate of &lt;0.6 M☉ yr-1 (4σ) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies (LIR/LUV) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at &gt; ${10}^{9.5}\,{M}_{\odot }$ and an SMC-like relation at lower masses. Using stellar mass and β measurements for z ∼ 2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between β and stellar mass and then use this correlation to show that our IRX-β and IRX-stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of β and stellar mass. Finally, we present updated estimates of star formation rate density determinations at z &gt; 3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at z &gt; 2.

Keywords: Far infrared astronomy, Infrared excess, Dust continuum emission, Lyman-break galaxies, High-redshift galaxies
The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Constraining the Molecular Content at log(M<SUB>*</SUB>/M<SUB>☉</SUB>) ∼ 9.5 with CO Stacking of MUSE-detected z ∼ 1.5 Galaxies. We report molecular gas mass estimates obtained from a stacking analysis of CO line emission in the ALMA Spectroscopic Survey (ASPECS) using the spectroscopic redshifts from the optical integral field spectroscopic survey by the Multi Unit Spectroscopic Explorer (MUSE) of the Hubble Ultra Deep Field (HUDF). Stacking was performed on subsets of the sample of galaxies classified by their stellar mass and position relative to the main-sequence relation (on, above, below). Among all the CO emission lines, from CO(2-1) to CO(6-5), with redshifts accessible via the ASPECS Band 3 and the MUSE data, CO(2-1) provides the strongest constraints on the molecular gas content. We detect CO(2-1) emission in galaxies down to stellar masses of $\mathrm{log}({M}_{* }/{M}_{\odot })=10.0$ . Below this stellar mass, we present a new constraint on the molecular gas content of $z\sim 1.5$ main-sequence galaxies by stacking based on the MUSE detections. We find that the molecular gas mass of main-sequence galaxies continuously decreases with stellar mass down to $\mathrm{log}({M}_{* }/{M}_{\odot })\approx 9.0$ . Assuming a metallicity-based CO-to-H2 conversion factor, the molecular gas-to-stellar mass ratio from $\mathrm{log}({M}_{* }/{M}_{\odot })\sim 9.0$ to ∼10.0 does not seem to decrease as fast as for $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.0$ , which is in line with simulations and studies at lower redshift. The inferred molecular gas density $\rho ({{\rm{H}}}_{2})=(0.49\pm 0.09)\times {10}^{8}\,{{\rm{M}}}_{\odot }\,{\mathrm{Mpc}}^{-3}$ of MUSE-selected galaxies at $z\sim 1.5$ is comparable with the one derived in the HUDF with a different CO selection. Using the MUSE data we recover most of the CO emission in our deep ALMA observations through stacking, demonstrating the synergy between volumetric surveys obtained at different wave bands.

Keywords: Molecular gas, Active galaxies, Galaxy evolution, High-redshift galaxies, Galaxies
Stellar X-Ray Activity Across the Hertzsprung-Russell Diagram. I. Catalogs. Stellar magnetic activity provides substantial information on the magnetic dynamo and the coronal heating process. We present a catalog of X-ray activity for about 6000 stars, based on the Chandra and Gaia DR2 data. We also classified more than 3000 stars as young stellar objects, dwarf stars, or giant stars. By using the stars with valid stellar parameters and classifications, we studied the distribution of X-ray luminosity (LX) and the ratio of X-ray-to-bolometric luminosities (RX), the positive relation between LX, RX, and hardness ratio, and the long-term X-ray variation. This catalog can be used to investigate some important scientific topics, including the activity-rotation relation, the comparison between different activity indicators, and the activities of interesting objects (e.g., A-type stars and giants). As an example, we use the catalog to study the activity-rotation relation, and find that the young stellar objects, dwarfs, and giants fall on a single sequence in the relation RX versus Rossby number, while the giants do not follow the relation RX versus ${P}_{\mathrm{rot}}^{-2}{R}^{-4}$ valid for dwarfs.

Keywords: Late-type stars, Stellar activity, Young stellar objects, X-ray stars, Giant stars