Sazuna/UAT_keywords huggingface dataset:
Resolution Study of Thermonuclear Initiation in White Dwarf Tidal Disruption Events. We study the initiation of thermonuclear detonations in tidally disrupted white dwarf stars by intermediate-mass (103 M ⊙) black holes. The length scales required to resolve the initiation mechanism are not easily reached in 3D, so instead we have devised 2D proxy models, which, together with a logarithmic gridding strategy, can adequately capture detonation wave fronts as material undergoes simultaneous compression and stretching from tidal forces. We consider 0.15 and 0.6 M ⊙ white dwarf stars parameterized by tidal strengths in the range β = 4-23. High spatial resolution elucidates the manner and conditions leading to thermonuclear detonation, linking the initiation sequence to stellar composition and tidal strength. All of our models suffer sustained detonations triggered by a combination of adiabatic compression, mild thermonuclear preconditioning, and collisional heating, in degrees depending primarily on tidal strength. We find that many diagnostics, such as temperature, total released energy, and iron-group products, are fairly well converged (better than 10%) at resolutions below 10 km along the scale height of the orbital plane. The exceptions are intermediate-mass transients like calcium, which remain uncertain up to factors of 2, even at 1 km resolution.

Keywords: Supermassive black holes, Radiative magnetohydrodynamics, Black holes, White dwarf stars, Astrophysical explosive burning, Astrophysical fluid dynamics, Astrophysical black holes
Study of the Very High Energy Emission of M87 through its Broadband Spectral Energy Distribution. The radio galaxy M87 is the central dominant galaxy of the Virgo Cluster. Very high-energy (VHE, ≳0.1 TeV) emission from M87 has been detected by imaging air Cherenkov telescopes. Recently, marginal evidence for VHE long-term emission has also been observed by the High Altitude Water Cherenkov Observatory, a gamma-ray and cosmic-ray detector array located in Puebla, Mexico. The mechanism that produces VHE emission in M87 remains unclear. This emission originates in its prominent jet, which has been spatially resolved from radio to X-rays. In this paper, we construct a spectral energy distribution from radio to gamma rays that is representative of the nonflaring activity of the source, and in order to explain the observed emission, we fit it with a lepto-hadronic emission model. We found that this model is able to explain nonflaring VHE emission of M87 as well as an orphan flare reported in 2005.

Keywords: Gamma-ray sources, Radio galaxies, Active galactic nuclei, Gamma-rays
Multiwavelength Observations by XSM, Hinode, and SDO of an Active Region. Chemical Abundances and Temperatures. We have reviewed the first year of observations of the Solar X-ray Monitor (XSM) on board Chandrayaan-2 and the available multiwavelength observations to complement the XSM data, focusing on the Solar Dynamics Observatory AIA and Hinode XRT and EIS observations. XSM has provided disk-integrated solar spectra in the 1-15 keV energy range, observing a large number of microflares. We present an analysis of multiwavelength observations of AR 12759 during its disk crossing. We use a new radiometric calibration of EIS to find that the quiescent active region (AR) core emission during its disk crossing has a distribution of temperatures and chemical abundances that does not change significantly over time. An analysis of the XSM spectra confirms the EIS results and shows that the low first ionization potential (FIP) elements are enhanced compared to their photospheric values. The frequent microflares produced by the AR did not affect the abundances of the quiescent AR core. We also present an analysis of one of the flares it produced, SOL2020-04-09T09:32. The XSM analysis indicates isothermal temperatures reaching 6 MK. The lack of very high-T emission is confirmed by AIA. We find excellent agreement between the observed XSM spectrum and the one predicted using an AIA DEM analysis. In contrast, the XRT Al-poly/Be-thin filter ratio gives lower temperatures for the quiescent and flaring phases. We show that this is due to the sensitivity of this ratio to low temperatures, as the XRT filter ratios predicted with a DEM analysis based on EIS and AIA give values in good agreement with the observed ones.

Keywords: Solar abundances, Solar active regions, Solar x-ray emission, Solar extreme ultraviolet emission
Galactic Winds across the Gas-rich Merger Sequence. II. Lyα Emission and Highly Ionized O VI and N V Outflows in Ultraluminous Infrared Galaxies. This paper is the second in a series aimed at examining the gaseous environments of z ≤ 0.3 quasars and ultraluminous infrared galaxies (ULIRGs) as a function of AGN/host galaxy properties across the merger sequence. This second paper focuses on the Lyα emission and O VI 1032, 1038 and N V 1238, 1243 absorption features, tracers of highly ionized gas outflows, in ULIRGs observed with HST/COS. Lyα emission is detected in 15 out of 19 ULIRGs, and 12 of the 14 clear Lyα detections show emission with blueshifted velocity centroids and/or wings. The equivalent widths of the Lyα emission increase with increasing AGN luminosities and AGN bolometric fractions. The blueshifts of the Lyα emission correlate positively with those of the [O III] λ5007 emission, where the latter traces the ionized gas outflows. The Lyα escape fractions tend to be slightly larger in objects with stronger AGN and larger outflow velocities, but they do not correlate with nebular line reddening. Among the 12 ULIRGs with good continuum signal-to-noise ratios, O VI and/or N V absorption features are robustly detected in six of them, all of which are blueshifted, indicative of outflows. In the combined ULIRG + quasar sample, the outflows are more frequently detected in the X-ray weak or absorbed sources. The absorption equivalent widths, velocities, and velocity dispersions of the outflows are also higher in the X-ray weak sources. No other strong correlations are visible between the properties of the outflows and those of the AGN or host galaxies.

Keywords: AGN host galaxies, Quasars, Active galactic nuclei, Galaxy evolution, Interstellar medium wind
Constraining Global Solar Models through Helioseismic Analysis. Global hydrodynamic simulations of internal solar dynamics have focused on replicating the conditions for solar-like (equator rotating faster than the poles) differential rotation and meridional circulation using the results of helioseismic inversions as a constraint. Inferences of meridional circulation, however, have provided controversial results showing the possibility of one, two, or multiple cells along the radius. To help address this controversy and develop a more robust understanding of global flow regimes in the solar interior, we apply a "forward-modeling" approach to the analysis of helioseismic signatures of meridional circulation profiles obtained from numerical simulations. We employ the global acoustic modeling code GALE to simulate the propagation of acoustic waves through regimes of mean mass-flows generated by global hydrodynamic and magnetohydrodynamic models: EULAG, the Pencil code, and the Rayleigh code. These models are used to create synthetic Dopplergram data products, used as inputs for local time-distance helioseismology techniques. Helioseismic travel-time signals from solutions obtained through global numerical simulations are compared directly with inferences from solar observations, in order to set additional constraints on global model parameters in a direct way. We show that even though these models are able to replicate solar-like differential rotation, the resulting rotationally constrained convection develops a multicell global meridional circulation profile that is measurably inconsistent with local time-distance inferences of solar observations. However, we find that the development of rotationally unconstrained convection close to the model surface is able to maintain solar-like differential rotation, while having a significant impact on the helioseismic travel-time signal, replicating solar observations within one standard deviation of the error due to noise.

Keywords: Helioseismology, Solar convective zone, Hydrodynamical simulations, Solar meridional circulation
Black Hole Mass Measurements of Early-type Galaxies NGC 1380 and NGC 6861 through ALMA and HST Observations and Gas-dynamical Modeling. We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations of CO(2-1) emission from the circumnuclear disks in two early-type galaxies, NGC 1380 and NGC 6861. The disk in each galaxy is highly inclined (i ~ 75°), and the projected velocities of the molecular gas near the galaxy centers are ~300 km s-1 in NGC 1380 and ~500 km s-1 in NGC 6861. We fit thin disk dynamical models to the ALMA data cubes to constrain the masses of the central black holes (BHs). We created host galaxy models using Hubble Space Telescope images for the extended stellar mass distributions and incorporated a range of plausible central dust extinction values. For NGC 1380, our best-fit model yields M BH = 1.47 × 108 M ⊙ with a ~40% uncertainty. For NGC 6861, the lack of dynamical tracers within the BH's sphere of influence due to a central hole in the gas distribution precludes a precise measurement of M BH. However, our model fits require a value for M BH in the range of (1-3) × 109 M ⊙ in NGC 6861 to reproduce the observations. The BH masses are generally consistent with predictions from local BH-host galaxy scaling relations. Systematic uncertainties associated with dust extinction of the host galaxy light and choice of host galaxy mass model dominate the error budget of both measurements. Despite these limitations, the measurements demonstrate ALMA's ability to provide constraints on BH masses in cases where the BH's projected radius of influence is marginally resolved or the gas distribution has a central hole. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with programs 15226 and 11712.

Keywords: Lenticular galaxies, Supermassive black holes, Elliptical galaxies
Formation of Dust Clumps with Sub-Jupiter Mass and Cold Shadowed Region in Gravitationally Unstable Disk around Class 0/I Protostar in L1527 IRS. We have investigated the protostellar disk around a Class 0/I protostar, L1527 IRS, using multiwavelength observations of the dust continuum emission at λ = 0.87, 2.1, 3.3, and 6.8 mm, obtained by the Atacama Large Millimeter/submillimeter Array and the Jansky Very Large Array (VLA). Our observations achieved a spatial resolution of 3-13 au and revealed an edge-on disk structure with a size of ~80-100 au. The emission at 0.87 and 2.1 mm is found to be optically thick, within a projected disk radius of r proj ≲ 50 au. The emission at 3.3 and 6.8 mm shows that the power-law index of the dust opacity (β) is β ~ 1.7 around r proj ~ 50 au, suggesting that grain growth has not yet begun. The dust temperature (T dust) shows a steep decrease with T dust ∝ r proj -2 outside the VLA clumps previously identified at r proj ~ 20 au. Furthermore, the disk is gravitationally unstable at r proj ~ 20 au, as indicated by a Toomre Q parameter value of Q ≲ 1.0. These results suggest that the VLA clumps are formed via gravitational instability, which creates a shadow on the outside of the substructure, resulting in the sudden drop in temperature. The derived dust masses for the VLA clumps are ≳0.1 M J. Thus, we suggest that Class 0/I disks can be massive enough to be gravitationally unstable, which may be the origin of gas giant planets in a 20 au radius. Furthermore, the protostellar disks could be cold due to shadowing.

Keywords: Young stellar objects, Dust continuum emission, Star formation, Interstellar medium, Circumstellar disks, Protostars, Planet formation
Monte Carlo Simulations of Electron Acceleration at Bow Waves Driven by Fast Jets in the Earth's Magnetosheath. The shocked solar wind flows around the Earth's magnetosphere in the magnetosheath downstream of the Earth's bow shock. Within this region, faster flows of plasma, called magnetosheath jets, are frequently observed. These jets have been shown to sometimes exhibit supermagnetosonic speeds relative to the magnetosheath flow and to develop bow waves or shocks of their own. Such jet-driven bow waves have been observed to accelerate ions and electrons. We model electron acceleration by magnetosheath jet-driven bow waves using test-particle Monte Carlo simulations. Our simulations suggest that the energy increase of electrons with energies of a few hundred eV to 10 keV can be explained by a collapsing magnetic trap forming between the bow wave and the magnetopause with shock drift acceleration at the moving bow wave. Our simulations allow us to estimate the efficiency of acceleration as a function of different jet and magnetosheath parameters. Electron acceleration by jet-driven bow waves can increase the total acceleration in the parent shock environment, most likely also at shocks other than the Earth's bow shock.

Keywords: Planetary magnetospheres, Planetary bow shocks, Solar-terrestrial interactions
Mapping the X-Ray Corona Evolution of IRAS 13224-3809 with the Power Spectral Density. We develop the power spectral density (PSD) model to explain the nature of the X-ray variability in IRAS 13224-3809, including the full effects of the X-ray reverberation due to the lamppost source. We utilize 16 XMM-Newton observations individually as well as group them into three different luminosity bins: low, medium, and high. The soft (0.3-1 keV) and hard (1.2-5 keV) PSD spectra are extracted and simultaneously fitted with the model. We find that the corona height changes from h ~ 3 r g during the lowest luminosity state to ~25 r g during the highest luminosity state. This provides further evidence that the source height from the reverberation data is significantly larger than what is constrained by the spectral analysis. Furthermore, as the corona height increases, the energy spectrum tends to be softer while the observed fractional excess variance, F var, reduces. We find that the PSD normalization is strongly correlated with F var and moderately correlated with the PSD bending index. Therefore, the normalization is dependent on the accretion rate that controls the intrinsic shape of the PSD. While the intrinsic variability of the disk is manifested by the reverberation signals, the disk and corona may evolve independently. Our results suggest that, as the source height increases, the disk itself generates less overall variability power but more high-frequency variability resulting in the PSD spectrum that flattens out (i.e., the inner disk becomes more active). Using the luminosity-bin data, the hint of the Lorentzian component is seen, with the peak appearing at lower frequencies with increasing luminosity.

Keywords: X-ray astronomy, Black hole physics, Reverberation mapping, Active galactic nuclei
New Spectroscopic Confirmations of Lyα Emitters at Z   7 from the LAGER Survey. We report spectroscopic confirmations of 15 Lyα galaxies at z ~ 7, implying a spectroscopic confirmation rate of ~80% on candidates selected from the Lyα Galaxies in the Epoch of Reionization (LAGER), which is the largest (24 deg2) survey aimed at finding Lyα emitters (LAEs) at z ~ 7 and uses deep narrowband imaging from the Dark Energy Camera at CTIO. LAEs at high redshifts are sensitive probes of cosmic reionization, and narrowband imaging is a robust and effective method for selecting a large number of LAEs. In this work, we present results from the spectroscopic follow-up of LAE candidates in two LAGER fields, COSMOS and WIDE-12, using observations from Keck/LRIS. We report the successful detection of Lyα emission in 15 candidates. Three of these in COSMOS have matching confirmations from a previous spectroscopic follow-up and are part of the overdense region, LAGER-z7OD1. Two other candidates that were not detected with LRIS have prior spectroscopic confirmations from Magellan. Including these, we obtain a spectroscopic confirmation success rate of ~80% for LAGER LAE candidates. Thorough checks were performed to reject the possibility of these detections being foreground emission resulting with a probability of, at most, one contaminant. We do not detect any other UV nebular lines in our LRIS spectra, apart from Lyα. We estimate a 2σ upper limit for the ratio of N V/Lyα, f NV/f Lyα  ≲ 0.27. Including confirmations from this work, a total of 33 LAE sources from LAGER are now spectroscopically confirmed. LAGER has more than doubled the sample of spectroscopically confirmed LAE sources at z ~ 7.

Keywords: Emission line galaxies, Galaxy evolution, Lyman-alpha galaxies, Reionization, High-redshift galaxies
The Broad Line Region and Black Hole Mass of NGC 4151. We present a reanalysis of reverberation mapping data from 2005 for the Seyfert galaxy NGC 4151, supplemented with additional data from the literature to constrain the continuum variations over a significantly longer baseline than the original monitoring program. Modeling of the continuum light curve and the velocity-resolved variations across the Hβ emission line constrains the geometry and kinematics of the broad line region (BLR). The BLR is well described by a very thick disk with similar opening angle (θ  o  ≈ 57°) and inclination angle (θ  i  ≈ 58°), suggesting that our sight line toward the innermost central engine skims just above the surface of the BLR. The inclination is consistent with constraints from geometric modeling of the narrow-line region, and the similarity between the inclination and opening angles is intriguing given previous studies of NGC 4151 that suggest BLR gas has been observed temporarily eclipsing the X-ray source. The BLR kinematics are dominated by eccentric bound orbits, with ~10% of the orbits preferring near-circular motions. With the BLR geometry and kinematics constrained, the models provide an independent and direct black hole mass measurement of $\mathrm{log}{M}_{\mathrm{BH}}/{M}_{\odot }={7.22}_{-0.10}^{+0.11}$ or ${M}_{\mathrm{BH}}={1.66}_{-0.34}^{+0.48}\times {10}^{7}$ M ⊙, which is in good agreement with mass measurements from stellar dynamical modeling and gas dynamical modeling. NGC 4151 is one of the few nearby broad-lined Seyferts where the black hole mass may be measured via multiple independent techniques, and it provides an important test case for investigating potential systematics that could affect the black hole mass scales used in the local universe and for high-redshift quasars.

Keywords: Supermassive black holes, Reverberation mapping, Seyfert galaxies
Line-of-sight Elongation and Hydrostatic Mass Bias of the Frontier Fields Galaxy Cluster Abell 370. We present a detailed weak-lensing and X-ray study of the Frontier Fields galaxy cluster Abell 370, one of the most massive known lenses on the sky, using wide-field BR C z' Subaru/Suprime-Cam and Chandra X-ray observations. By combining two-dimensional (2D) shear and azimuthally averaged magnification constraints derived from Subaru data, we perform a lensing mass reconstruction in a free-form manner, which allows us to determine both the radial structure and 2D morphology of the cluster mass distribution. In a triaxial framework assuming a Navarro-Frenk-White density profile, we constrain the intrinsic structure and geometry of the cluster halo by forward modeling the reconstructed mass map. We obtain a halo mass M 200 = (1.54 ± 0.29) ×1015 h -1 M ⊙, a halo concentration c 200 = 5.27 ± 1.28, and a minor-major axis ratio q  a  = 0.62 ± 0.23 with uninformative priors. Using a prior on the line-of-sight alignment of the halo major axis derived from binary merger simulations constrained by multi-probe observations, we find that the data favor a more prolate geometry with lower mass and lower concentration. From triaxial lens modeling with the line-of-sight prior, we find a spherically enclosed gas mass fraction of f gas = (8.4 ± 1.0)% at 0.7 h -1 Mpc ~ 0.7r 500. When compared to the hydrostatic mass estimate (M HE) from Chandra observations, our triaxial weak-lensing analysis yields spherically enclosed mass ratios of 1 - b ≡ M HE/M WL = 0.56 ± 0.09 and 0.51 ± 0.09 at 0.7 h -1 Mpc with and without using the line-of-sight prior, respectively. Since the cluster is in a highly disturbed dynamical state, this represents the likely maximum level of hydrostatic bias in galaxy clusters.

Keywords: Galaxy clusters, Weak gravitational lensing, Dark matter distribution, X-ray astronomy, Cold dark matter, Intracluster medium
High-resolution, High-sensitivity, Low-frequency uGMRT View of Coma Cluster of Galaxies. We present high-resolution, high-sensitivity upgraded Giant Metrewave Radio Telescope observations of the Coma cluster (A1656) at 250-500 MHz and 550-850 MHz. At 250-500 MHz, 135 sources have extensions &gt;0.'45 (with peak-to-local-noise ratio &gt;4). Of these, 24 sources are associated with Coma-member galaxies. In addition, we supplement this sample of 24 galaxies with 20 ram pressure stripped (RPS) galaxies from (Chen et al. 2020, eight are included in the original extended radio source sample) and an additional five are detected and extended. We present radio morphologies, radio spectra, spectral index maps, and equipartition properties for these two samples. In general, we find the equipartition properties lie within a narrow range (e.g., ${P}_{\min }$ = 1-3 × 10- 13 dynes cm-2). Only NGC 4874, one of the two brightest central Coma cluster galaxies, has a central energy density and pressure about five times higher and a radio source age about 50% lower than that of the other Coma galaxies. We find a diffuse tail of radio emission trailing the dominant galaxy of the merging NGC 4839 group that coincides with the slingshot tail seen in X-rays. The southwestern radio relic, B1253+275, has a large extent ≍32' × 10' (≃1.08 × 0.34 Mpc2). For NGC 4789, whose long radio tails merge into the relic and may be a source of its relativistic seed electrons, we find a transverse radio spectral gradient, a steepening from southwest to northeast across the width of the radio source. Finally, radio morphologies of the extended and RPS samples suggest that these galaxies are on their first infall into Coma on (predominantly) radial orbits.

Keywords: Galaxy clusters, Supermassive black holes, High energy astrophysics, Coma Cluster, Radio galaxies, X-ray active galactic nuclei, Tailed radio galaxies, Radio continuum emission, Intracluster medium, Astrophysical black holes