Sazuna/UAT_keywords huggingface dataset:
Probing the Halo Gas Distribution in the Inner Galaxy with Fermi Bubble Observations. The hot halo gas distribution in the inner Milky Way (MW) contains key fossil records of the past energetic feedback processes in the galactic center. Here, we adopt a variety of spherical and disk-like MW halo gas models as initial conditions in a series of simulations to investigate the formation of the Fermi bubbles in the jet-shock scenario. The simulation results are compared directly with relevant X-ray and gamma-ray observations of the Fermi bubbles to constrain the halo gas distribution in the inner Galaxy before the Fermi bubble event. Our best-fit gas density distribution can be described by a power law in radius ne(r) = 0.01(r/1 kpc)-1.5 cm-3. Our study cannot determine if there is an inner density core, which if exists, should be very small with size rc ≲ 0.5 kpc. When extrapolating to large radii r ~ 50-90 kpc, our derived density distribution lies appreciably below the recently estimated gas densities from ram pressure stripping calculations, suggesting that the halo gas density profile either flattens out or has one or more discontinuities within 10 ≲ r ≲ 50 kpc. Some of these discontinuities may be related to the eROSITA bubbles, and our derived gas density profile may correspond to the hot gas distribution in the inner eROSITA bubbles about 5 Myr ago.

Keywords: X-ray astronomy, Galactic winds, Galactic center, Jets, Active galaxies, Galaxy jets, Computational methods, Circumgalactic medium, Shocks, Gamma-rays, Milky Way Galaxy, Cosmic rays
Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3a. We search for gravitational-wave transients associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the first part of the third observing run of Advanced LIGO and Advanced Virgo (2019 April 1 15:00 UTC-2019 October 1 15:00 UTC). A total of 105 GRBs were analyzed using a search for generic gravitational-wave transients; 32 GRBs were analyzed with a search that specifically targets neutron star binary mergers as short GRB progenitors. We find no significant evidence for gravitational-wave signals associated with the GRBs that we followed up, nor for a population of unidentified subthreshold signals. We consider several source types and signal morphologies, and report for these lower bounds on the distance to each GRB.

Keywords: Neutron stars, Gamma-ray bursts, Black holes, Compact binary stars, Gravitational wave astronomy, Gravitational waves, LIGO
Dissecting the Size-Mass and Σ<SUB>1</SUB>-Mass Relations at 1.0 &lt; z &lt; 2.5: Galaxy Mass Profiles and Color Gradients as a Function of Spectral Shape. We study how half-mass radii, central mass densities (Σ1), and color gradients change as galaxies evolve. We separate ~7000 galaxies into 16 groups with similar spectral shapes; each group represents a different evolutionary stage. We find that different galaxy types populate different regions of both size-mass and Σ1-mass space. The nine star-forming groups lie along the integrated star-forming Σ1-mass relation. However, these star-forming groups form steep parallel relations in the size-mass plane, with slopes similar to the quiescent size-mass relation. These steep slopes can be explained as a transformation of the star-forming Σ1-mass relation and its scatter. We identify three types of transitional galaxies. Green valley and post-starburst galaxies are similarly compact at z &gt; 1.5; however, their distinct color gradients indicate that the two populations represent different pathways to quenching. Post-starburst galaxies have flat color gradients and compact structures, consistent with a fast quenching pathway that requires structural change and operates primarily at high redshift. Green valley galaxies have negative color gradients, and are both larger and more numerous toward lower redshift. These galaxies are consistent with slow quenching without significant structural change. We find that dusty star-forming galaxies at z ≳ 2 are very compact and may represent the "burst" before post-starburst galaxies; at z ≲ 2, dusty star-forming galaxies are extended and have shallow color gradients consistent with slow quenching. Our results suggest that star-forming galaxies grow gradually up the Σ1-mass relation until (a) they naturally reach the high Σ1 values required for quiescence or (b) a compaction-type event rapidly increases their Σ1.

Keywords: Compact galaxies, Galaxy structure, Green valley galaxies, Galaxy evolution, Galaxy quenching, Post-starburst galaxies
A Forecast of the Sensitivity on the Measurement of the Optical Depth to Reionization with the GroundBIRD Experiment. We compute the expected sensitivity on measurements of optical depth to reionization for a ground-based experiment at Teide Observatory. We simulate polarized partial sky maps for the GroundBIRD experiment at the frequencies 145 and 220 GHz. We perform fits for the simulated maps with our pixel-based likelihood to extract the optical depth to reionization. The noise levels of polarization maps are estimated as 110 $\mu {\rm{K}}\,\mathrm{arcmin}$ and 780 $\mu {\rm{K}}\,\mathrm{arcmin}$ for 145 and 220 GHz, respectively, by assuming a three-year observing campaign and sky coverages of 0.537 for 145 GHz and 0.462 for 220 GHz. Our sensitivities for the optical depth to reionization are found to be στ = 0.030 with the simulated GroundBIRD maps, and στ = 0.012 by combining with the simulated QUIJOTE maps at 11, 13, 17, 19, 30, and 40 GHz.

Keywords: Early universe, Cosmic microwave background radiation, Photon decoupling, Cosmological parameters
Circumnuclear Multi-phase Gas in Circinus Galaxy IV: Absorption Owing to High-J CO Rotational Transitions. We studied the absorption features of CO lines against the continuum originating from the heated dust in the obscuring tori around active galactic nuclei (AGNs). We investigated the formation of absorption lines corresponding to the CO rotational transitions using three-dimensional non-LTE line transfer simulations considering the dust thermal emission. As in Papers I-III of this series, we performed post-processed radiative transfer calculations using the "radiation-driven fountain model" (Wada et al. 2016), which yields a geometrically thick obscuring structure around the nucleus. This model is consistent with the spectral energy distribution of the nearest type-2 Seyfert galaxy, the Circinus galaxy. We found that the continuum-subtracted channel maps of J = 4-3 and higher transitions show absorption regions along the disk midplane for an edge-on viewing angle. The spectra consist of multiple absorption and emission features, reflecting the internal inhomogeneous and turbulent structure of the torus. The deepest absorption feature is caused by the gas on the near side of the torus between r = 10 and 15 pc, which is located in front of the AGN-heated dust inside r ≃ 5 pc. We also found that a spatial resolution of 0.5-1.0 pc is necessary to resolve the absorption features. Moreover, the inclination angle must be close to the edge-on angle (i.e., ≳85°) to observe the absorption features. The findings of the present study imply that combining our radiation-hydrodynamic model with high-resolution observations of CO (7-6) by ALMA can provide new information about the internal structure of the molecular tori in nearby AGNs.

Keywords: Active galaxies, Active galactic nuclei, Radio astrometry
Photoevaporation of Grain-depleted Protoplanetary Disks around Intermediate-mass Stars: Investigating the Possibility of Gas-rich Debris Disks as Protoplanetary Remnants. Debris disks are classically considered to be gas-less systems, but recent (sub)millimeter observations have detected tens of those with rich gas content. The origin of the gas component remains unclear, but it could be protoplanetary remnants and/or secondary products from large bodies. In order to be protoplanetary in origin, the gas component of the parental protoplanetary disk is required to survive for $\gtrsim 10\,\mathrm{Myr}$ . However, previous models predict $\lesssim 10\,\mathrm{Myr}$ lifetimes because of efficient photoevaporation at the late stage of disk evolution. We investigate photoevaporation of gas-rich, optically-thin disks around intermediate-mass stars at a late stage of the disk evolution. The evolved system is modeled like those devoid of small grains ( $\lesssim 4\,\mu {\rm{m}}$ ). We find that grain depletion reduces photoelectric heating so that far-ultraviolet photoevaporation is not excited. Extreme-ultraviolet (EUV) photoevaporation is dominant and yields a mass-loss rate of the order of $1\times {10}^{-11}{({{\rm{\Phi }}}_{\mathrm{EUV}}/{10}^{38}{{\rm{s}}}^{-1})}^{1/2}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , where ${{\rm{\Phi }}}_{\mathrm{EUV}}$ is the EUV emission rate of the host star. The estimated gas-disk lifetimes are $\sim 100{({M}_{\mathrm{disk}}/{10}^{-3}{M}_{\odot })({{\rm{\Phi }}}_{\mathrm{EUV}}/{10}^{38}{{\rm{s}}}^{-1})}^{1/2}\,\mathrm{Myr}$ and depend on the "initial" disk mass at the point small grains have been depleted in the system. We show that the gas component can survive for a much longer time around A-type stars than lower-mass (F-, G-, K-type) stars owing to their atypical low EUV (and X-ray) luminosities. This trend is consistent with the higher frequency of gas-rich debris disks around A-type stars, implying the possibility of the gas component being protoplanetary remnants.

Keywords: Hydrodynamical simulations, Planetary system formation, Star formation, Protoplanetary disks, Debris disks
Orbital Migration and Circularization of Tidal Debris by Alfvén-wave Drag: Circumstellar Debris and Pollution around White Dwarfs. A significant fraction of white dwarfs (WDs) exhibit signs of ongoing accretion of refractory elements at rates ~103-107 kg s-1, among which, 37 WDs were detected to harbor dusty debris disks. Such a concurrence requires not only fertile reservoirs of planetary material but also a high duty cycle of metal delivery. It has been commonly suggested that this material could be supplied by solar system analogs of Main Belt asteroids or Kuiper Belt objects. Here we consider the primary progenitors of WD pollutants as a population of residual high-eccentricity planetesimals, devolatilized during the stellar giant phases. Equivalent to the solar system's long-period comets, they are scattered to the proximity of WDs by perturbations from remaining planets, Galactic tides, passing molecular clouds, and nearby stars. These objects undergo downsizing when they venture within the tidal disruption limit. We show quantitatively how the breakup condition and fragment sizes are determined by material strength and gravity. Thereafter, the fragments' semimajor axes need to decay by at least ~6 orders of magnitude before their constituents are eventually accreted onto the surface of WDs. We investigate the orbital evolution of these fragments around WDs and show that WDs' magnetic fields induce an Alfvén-wave drag during their periastron passages and rapidly circularize their orbits. This process could be responsible for the observed accretion rates of heavy elements and the generation of circum-WD debris disks. Speculative implications are that giant planets may be common around WDs' progenitors and that they may still be bound to some WDs today.

Keywords: Exoplanet dynamics, Asteroids, White dwarf stars, Exoplanet evolution, Debris disks
Characterizing the Multiphase Origin of [C II] Emission in M101 and NGC 6946 with Velocity-resolved Spectroscopy. The [C II] fine-structure transition at 158 μm is frequently the brightest far-infrared line in galaxies. Due to its low ionization potential, C+ can trace the ionized, atomic, and molecular phases of the ISM. We present velocity-resolved [C II] and [N II] pointed observations from SOFIA/GREAT on ~500 pc scales in the nearby galaxies M101 and NGC 6946 and investigate the multiphase origin of [C II] emission over a range of environments. We show that ionized gas makes a negligible contribution to the [C II] emission in these positions using [N II] observations. We spectrally decompose the [C II] emission into components associated with the molecular and atomic phases using existing CO (2-1) and H I data and show that a peak signal-to-noise ratio of 10-15 is necessary for a reliable decomposition. In general, we find that in our pointings ≳50% of the [C II] emission arises from the atomic phase, with no strong dependence on star formation rate, metallicity, or galactocentric radius. We do find a difference between pointings in these two galaxies, where locations in NGC 6946 tend to have larger fractions of [C II] emission associated with the molecular phase than in M101. We also find a weak but consistent trend for fainter [C II] emission to exhibit a larger contribution from the atomic medium. We compute the thermal pressure of the cold neutral medium through the [C II] cooling function and find $\mathrm{log}({P}_{\mathrm{th}}/k)=3.8\mbox{--}4.6\,\,[{\rm{K}}\ \,{\mathrm{cm}}^{-3}]$ , a value slightly higher than similar determinations, likely because our observations are biased toward star-forming regions.

Keywords: Molecular gas, Spiral galaxies, Photodissociation regions, Far infrared astronomy, Cold neutral medium, Interstellar medium
A Weakening Compton Hump and Soft X-Ray Excess Detected in the Seyfert 1 Galaxy MCG -02-58-22. We have carried out an extensive X-ray spectral study of the bare Seyfert 1 galaxy MCG -02-58-22 to ascertain the nature of the X-ray reprocessing media using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016). The most significant results of our investigation are as follows. (1) The primary X-ray emission from the corona is constant in these observations, in terms of both the power-law slope (Γ = 1.80) and luminosity (L2-10 keV = 2.55 × 1044 erg s-1). (2) The soft excess flux decreased by a factor of 2 in 2016, the Compton hump weakened/vanished in 2016, and the narrow FeKα emission line became marginally broad (σ = 0.35 ± 0.08 keV) and its flux doubled in 2016. (3) From physical model fits, we find that the normalization of the narrow component of the FeKα line does not change in the two epochs, although the Compton hump vanishes in the same time span. Since the primary X-ray continuum does not change, we presume that any changes in the reprocessed emission must arise due to changes in the reprocessing media. Our primary conclusions are as follows. (a) The vanishing of the Compton hump in 2016 can probably be explained by a dynamic clumpy torus that is infalling/outflowing or a polar dusty wind. (b) The torus in this active galactic nucleus possibly has two structures: an equatorial toroidal disk (producing the narrow FeKα emission) and a polar component (producing the variable Compton hump). (c) The reduction of the soft excess flux by half and increase in the FeKα flux by a factor of 2 in the same period cannot be adequately explained by an ionized disk reflection model alone.

Keywords: Active galaxies, Active galactic nuclei, X-ray active galactic nuclei
From Haloes to Galaxies. III. The Gas Cycle of Local Galaxy Populations. In Dou et al., we introduced the fundamental formation relation (FFR), a tight relation between specific star formation rate (sSFR), H2 star formation efficiency (SFE ${}_{{{\rm{H}}}_{2}}$ ), and the ratio of H2 to stellar mass. Here, we show that atomic gas H ɪ does not follow a similar FFR as H2. The relation between SFEHɪ and sSFR shows significant scatter and strong systematic dependence on all of the key galaxy properties that we have explored. The dramatic difference between H ɪ and H2 indicates that different processes (e.g., quenching by different mechanisms) may have very different effects on H ɪ in different galaxies and hence produce different SFEHɪ-sSFR relations, while the SFE ${}_{{{\rm{H}}}_{2}}$ -sSFR relation remains unaffected. The fact that the SFE ${}_{{{\rm{H}}}_{2}}$ -sSFR relation is independent of other key galaxy properties, and that sSFR is directly related to the cosmic time and acts as the cosmic clock, make it natural and very simple to study how different galaxy populations (with different properties and undergoing different processes) evolve on the same SFE ${}_{{{\rm{H}}}_{2}}$ -sSFR ~ t relation. In the gas regulator model (GRM), the evolution of a galaxy on the SFE ${}_{{{\rm{H}}}_{2}}$ -sSFR(t) relation is uniquely set by a single mass-loading parameter ${\lambda }_{\mathrm{net},{{\rm{H}}}_{2}}$ . This simplicity allows us to accurately derive the H2 supply and removal rates of the local galaxy populations with different stellar masses, from star-forming galaxies to the galaxies in the process of being quenched. This combination of FFR and GRM, together with the stellar metallicity requirement, provide a new powerful tool to study galaxy formation and evolution.

Keywords: Galaxy formation, Star formation, Galaxy evolution, Interstellar medium, Galaxy quenching
Variations in the Pickup Ion Density Structure in Response to the Growth of the Kelvin-Helmholtz Instability along the Heliopause. Features of the response of pickup ions (PUIs) to the Kelvin-Helmholtz instability (KHI) on the heliopause (HP) are examined by means of two-dimensional hybrid simulations. We assume the supersonic neutral solar wind as the source of PUIs gyrating about the magnetic field in the outer heliosheath. These PUIs become energetic neutral atoms (ENAs) via charge exchange with interstellar hydrogen, and a portion of these ENAs are detected by spacecraft such as the Interstellar Boundary Explorer (IBEX). To evaluate the possibility of identifying the KHI on the HP from ENA observations, we assume that an imprint of the KHI may be displayed in spatial and temporal variations in the observed ENA profile. As an alternative to ENA, the column density of PUIs integrated across the HP is calculated. The KH-inducing vortex forces not only background protons but also PUIs to roll up deep in the inner heliosheath. The KH vortex also results in the emission of magnetosonic pulses that sweep PUIs in the outer heliosheath and lead to their local confinement. These effects elongate the PUIs' spatial distribution in the direction normal to the HP. The appearance of the local confined structure in the PUIs' column density is consequently confirmed, and this feature can be confirmed as the KHI evolution. Although the simulation cannot be quantitatively compared with the observations currently available because its resolution is too low, we expect that the derived properties will be useful for diagnosing the nature of HP fluctuation in future missions.

Keywords: Heliopause, Heliosphere, Solar wind, Pickup ions, Heliosheath
Mapping Solar X-Ray Images from SDO/AIA EUV Images by Deep Learning. The full-Sun corona is now imaged every 12 s in extreme ultraviolet (EUV) passbands by Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), whereas it is only observed several times a day at X-ray wavelengths by Hinode/X-Ray Telescope (XRT). In this paper, we apply a deep-learning method, i.e., the convolution neural network (CNN), to establish data-driven models to generate full-Sun X-ray images in XRT filters from AIA EUV images. The CNN models are trained using a number of data pairs of AIA six-passband (171, 193, 211, 335, 131, and 94 Å) images and the corresponding XRT images in three filters: "Al_mesh," "Ti_poly," and "Be_thin." It is found that the CNN models predict X-ray images in good consistency with the corresponding well-observed XRT data. In addition, the purely data-driven CNN models are better than the conventional analysis method of the coronal differential emission measure (DEM) in predicting XRT-like observations from AIA data. Therefore, under conditions where AIA provides coronal EUV data well, the CNN models can be applied to fill the gap in limited full-Sun coronal X-ray observations and improve pool-observed XRT data. It is also found that DEM inversions using AIA data and our deep-learning-predicted X-ray data jointly are better than those using AIA data alone. This work indicates that deep-learning methods provide the opportunity to study the Sun based on virtual solar observation in future.

Keywords: Active solar corona, Solar atmosphere, Quiet solar corona, Solar corona
Multimessenger Pulsar Timing Array Constraints on Supermassive Black Hole Binaries Traced by Periodic Light Curves. Supermassive black hole binary systems (SMBHBs) emitting gravitational waves may be traced by periodic light curves. We assembled a catalog of 149 such periodic light curves, and using their masses, distances, and periods, predicted the gravitational-wave strain and detectability of each binary candidate using all-sky detection maps. We found that the International Pulsar Timing Array (IPTA) provides almost uniform sky coverage-a unique ability of the IPTA-and by 2025 will improve NANOGrav's current minimum detectable strain by a factor of 6 and its volume by a factor of 216. Moreover, IPTA will reach detection sensitivities for three candidates by 2025, and 13 by the end of the decade, enabling us to constrain the underlying empirical relations used to estimate supermassive black hole masses. We find that we can in fact already constrain the mass of a binary in Mrk 504 to M &lt; 3.3 × 109 M⊙. We also identify 24 high-mass, high-redshift galaxies that, according to our models, should not be able to host SMBHBs. Importantly, the GW detection of even one of these candidates would be an essentially eternal multimessenger system, and identifying common false-positive signals from nondetections will be useful to filter the data from future large-scale surveys such as LSST.

Keywords: AGN host galaxies, Supermassive black holes, Millisecond pulsars, Gravitational wave sources, Gravitational wave astronomy, Active galactic nuclei, Gravitational waves, General relativity, Astrophysical black holes
Multi-scale Radio and X-Ray Structure of the High-redshift Quasar PMN J0909+0354. The high-redshift quasar PMN J0909+0354 (z = 3.288) is known to have a parsec-scale compact jet structure, based on global 5 GHz very long baseline interferometry (VLBI) observations performed in 1992. Its kiloparsec-scale structure was studied with the Karl G. Jansky Very Large Array (VLA) in the radio and the Chandra space telescope in X-rays. Apart from the north-northwestern jet component seen in both the VLA and Chandra images at 2"3 separation from the core, there is another X-ray feature at 6"48 in the northeastern (NE) direction. To uncover more details and possible structural changes in the inner jet, we conducted new observations at 5 GHz using the European VLBI Network in 2019. These data confirm the northward direction of the one-sided inner jet already suspected from the 1992 observations. A compact core and multiple jet components were identified that can be traced up to ~0.25 kpc projected distance toward the north, where the structure becomes more and more diffuse. A comparison with arcsecond-resolution imaging with the VLA shows that the radio jet bends by ~30° between the two scales. The direction of the parsec-scale jet as well as the faint optical counterpart found for the newly detected X-ray point source (NE) favors the nature of the latter as being a background or foreground object in the field of view. However, the extended (~160 kpc) emission around the positions of the quasar core and NE detected by the Wide-field Infrared Survey Explorer in the mid-infrared might suggest a physical interaction of the two objects.

Keywords: Jets, Quasars, Blazars, X-ray active galactic nuclei, Active galactic nuclei, Radio continuum emission