Sazuna/UAT_keywords huggingface dataset:
Supernova Ejecta Interacting with a Circumstellar Disk. I. Two-dimensional Radiation-hydrodynamic Simulations. We perform a series of two-dimensional radiation-hydrodynamic simulations of the collision between supernova ejecta and circumstellar media (CSMs). The hydrodynamic interaction of a fast flow and the surrounding media efficiently dissipates the kinetic energy of the fast flow and is considered as a dominant energy source for a specific class of core-collapse supernovae. Despite some observational evidence for aspherical ejecta and/or CSM structure, multidimensional effects in the ejecta-CSM interaction are relatively unexplored. Our numerical simulations equipped with an adaptive mesh refinement technique successfully reproduce hydrodynamic instabilities developing around the ejecta-CSM interface. We also investigate effects of disklike CSMs on the dynamical evolution of supernova ejecta and bolometric light curves. We find that emission powered by ejecta-disk interaction exhibits significant viewing angle dependence. For a line of sight close to the symmetry axis, the observer directly sees the supernova ejecta, leading to a short brightening timescale. For an observer seeing the emission through the CSM disk, thermal photons diffuse throughout the CSM, and thus the light curve is severely smeared out.

Keywords: Hydrodynamical simulations, Hydrodynamics, Radiative transfer, Shocks, Circumstellar gas, Supernovae, Stellar evolution
Deciphering Residual Emissions: Time-dependent Models for the Nonthermal Interstellar Radiation from the Milky Way. Cosmic rays (CRs) in the Galaxy are an important dynamical component of the interstellar medium (ISM) that interact with the other major components (interstellar gas and magnetic and radiation fields) to produce broadband interstellar emissions that span the electromagnetic spectrum. The standard modeling of CR propagation and production of the associated emissions is based on a steady-state assumption, where the CR source spatial density is described using a smoothly varying function of position that does not evolve with time. While this is a convenient approximation, reality is otherwise, where primary CRs are produced in and about highly localized regions, e.g., supernova remnants, which have finite lifetimes. In this paper, we use the latest version of the GALPROP CR propagation code to model time-dependent CR injection and propagation through the ISM from a realistic 3D discretized CR source density distribution, together with full 3D models for the other major ISM components, and make predictions of the associated broadband nonthermal emissions. We compare the predictions for the discretized and equivalent steady-state model, finding that the former predicts novel features in the broadband nonthermal emissions that are absent for the steady-state case. Some of the features predicted by the discretized model may be observable in all-sky observations made by WMAP and Planck, the recently launched eROSITA, the Fermi-LAT, and ground-based observations by HESS, HAWC, and the forthcoming CTA. The nonthermal emissions predicted by the discretized model may also provide explanations of puzzling anomalies in high-energy γ-ray data, such as the Fermi-LAT north/south asymmetry and residuals like the so-called “Fermi bubbles.”

Keywords: Extended radiation sources, Interstellar emissions, Interstellar medium, Gamma-rays, Particle astrophysics, Cosmic rays
The Star-forming Interstellar Medium of Lyman Break Galaxy Analogs. We present Very Large Telescope SINFONI near-infrared (NIR) integral field spectroscopy of six z ∼ 0.2 Lyman break galaxy “analogs” (LBAs) from which we detect H I, He I, and [Fe II] recombination lines and multiple H2 rovibrational lines in emission. The Paα kinematics reveal high velocity dispersions and low rotational velocities relative to random motions (&lt; {V}rot}/σ &gt; =1.2+/- 0.8). Matched-aperture comparisons of Hβ, Hα, and Paα reveal that the nebular color excesses are lower relative to the continuum color excesses than is the case for typical local star-forming systems. We compare observed He I/H I recombination line ratios to photoionization models to gauge the effective temperatures (T eff) of massive ionizing stars, finding that the properties of at least one LBA are consistent with extra heating from an active galactic nucleus (AGN) and/or an overabundance of massive stars. We use H2 1-0 S(·) rovibrational spectra to determine a rotational excitation temperature T ex ∼ 2000 K for warm molecular gas, which we attribute to UV heating in dense photon-dominated regions. Spatially resolved NIR line ratios favor excitation by massive young stars, rather than supernova or AGN feedback. Our results suggest that the local analogs of Lyman break galaxies are primarily subject to strong feedback from recent star formation, with evidence for AGNs and outflows in some cases.

Keywords: Observational astronomy, Starburst galaxies, Compact galaxies, Galaxy kinematics, Galaxy evolution, Galaxy winds, Interstellar medium, Lyman-break galaxies, High-redshift galaxies
A Deep Targeted Search for Fast Radio Bursts from the Sites of Low-redshift Short Gamma-Ray Bursts. Some short gamma-ray bursts (SGRBs) are thought to be caused by the mergers of binary neutron stars which may sometimes produce massive neutron star remnants capable of producing extragalactic fast radio bursts (FRBs). We conducted a deep search for FRBs from the sites of six low-redshift SGRBs. We collected high time- and frequency-resolution data from each of the sites for 10 hr using the 2 GHz receiver of the Green Bank Telescope (GBT). Two of the SGRB sites we targeted were visible with the Arecibo Radio Telescope with which we conducted an additional 10 hr of 1.4 GHz observations for each. We searched our data for FRBs using the GPU-optimized dedispersion algorithm HEIMDALL and the machine-learning-based package Fast Extragalactic Transient Candidate Hunter. We did not discover any FRBs, but would have detected any with peak flux densities in excess of 87 mJy at the GBT or 21 mJy at Arecibo with a signal-to-noise ratio of at least 10. The isotropic-equivalent energy of any FRBs emitted from these sites in our bands during our observations must not have exceeded a few times 1038 erg, comparable to some of the lowest energy bursts yet seen from the first known repeating FRB 121102.

Keywords: Radio bursts, Gamma-ray bursts, Radio astronomy, Transient sources
Exploring the Convective Core of the Hybrid δ Scuti-γ Doradus Star CoRoT 100866999 with Asteroseismology. We computed a grid of theoretical models to fit the δ Scuti frequencies of CoRoT 100866999 detected earlier from the CoRoT time serials. The pulsating primary star is determined to be a main-sequence star with a rotation period of {4.1}-0.5+0.6 days, rotating slower than the orbital motion. The fundamental parameters of the primary star are determined to be M={1.71}-0.04+0.13 {M}⊙ , Z={0.012}-0.000+0.004, {f}ov}={0.02}-0.02+0.00, {T}eff}={8024}-297+249 K, L={11.898}-1.847+2.156 {L}⊙ , {log}g={4.166}-0.002+0.013, R={1.787}-0.016+0.040 {R}⊙ , and {X}{{c}}={0.488}-0.020+0.011, matching those obtained from the eclipsing light-curve analysis. Based on the model fittings, p 1 and p 5 are suggested to be two dipole modes, and p 3, p 4, p 6, and p 7 are suggested to be four quadrupole modes. In particular, p 4 and p 7 are identified as two components of one quintuplet. Based on the best-fitting model, we find that p 1 is a g mode and the other nonradial modes have pronounced mixed characters, which give strong constraints on the convective core. Finally, the relative size of the convective core of CoRoT 100866999 is determined to {R}conv}/R={0.0931}-0.0013+0.0003.

Keywords: Gamma Doradus variable stars, Asteroseismology, Delta Scuti variable stars, Pulsating variable stars
GRB 180620A: Evidence for Late-time Energy Injection. The early optical emission of gamma-ray bursts (GRBs) gives an opportunity to understand the central engine and first stages of these events. About 30% of GRBs present flares whose origin is still a subject of discussion. We present optical photometry of GRB 180620A with the COATLI telescope and RATIR instrument. COATLI started to observe from the end of prompt emission at T + 39.3 s and RATIR from T + 121.4 s. We supplement the optical data with the X-ray light curve from Swift/XRT. We observe an optical flare from T + 110 s to T + 550 s, with a temporal index decay α O,decay = 1.32 ± 0.01, and Δt/t = 1.63, which we interpret as the signature of a reverse shock component. After the initial normal decay the light curves show a long plateau from T + 500 s to T + 7800 s in both X-rays and the optical before decaying again after an achromatic jet break at T + 7800 s. Fluctuations are seen during the plateau phase in the optical. Adding to the complexity of GRB afterglows, the plateau phase (typically associated with the coasting phase of the jet) is seen in this object after the “normal” decay phase (associated with the deceleration phase of the jet), and the jet break phase occurs directly after the plateau. We suggest that this sequence of events can be explained by a rapid deceleration of the jet with t  d  ≲ 40 s due to the high density of the environment (≈100 cm-3) followed by reactivation of the central engine, which causes the flare and powers the plateau phase.

Keywords: Gamma-ray sources, Gamma-ray bursts, Optical telescopes, Gamma-ray bursters
The Broadband X-Ray Spectrum of the X-Ray-obscured Type 1 AGN 2MASX J193013.80+341049.5. We present results from modeling the broadband X-ray spectrum of the Type 1 active galactic nucleus (AGN) 2MASX J193013.80+341049.5 using NuSTAR, Swift, and archival XMM-Newton observations. We find this source to be highly X-ray obscured, with column densities exceeding 1023 cm-2 across all epochs of X-ray observations, spanning an 8 yr period. However, the source exhibits prominent broad optical emission lines, consistent with an unobscured Type 1 AGN classification. We fit the X-ray spectra with both phenomenological reflection models and physically motivated torus models to model the X-ray absorption. We examine the spectral energy distribution of this source and investigate some possible scenarios to explain the mismatch between X-ray and optical classifications. We compare the ratio of reddening to X-ray absorbing column density ({E}B-V/{N}{{H}}) and find that 2MASX J193013.80+341049.5 likely has a much lower dust-to-gas ratio relative to the Galactic interstellar medium, suggesting that the broad line region itself could provide the source of extra X-ray obscuration, being composed of low-ionization, dust-free gas.

Keywords: X-ray astronomy, Seyfert galaxies, Active galactic nuclei
Thermal Instability of Thin Accretion Disks in the Presence of Wind and a Toroidal Magnetic Field. We study the local thermal stability of thin accretion disks. We present a full stability analysis in the presence of a magnetic field and, more importantly, wind. We use a general model suitable for adequately describing several kinds of winds. First, we explicitly show that the magnetic field, irrespective of the type of wind, has a stabilizing effect. This is also true when there is no wind. In this case, we confirm other works presented in the literature. However, our main objective is to investigate the local thermal stability of the disk in the presence of wind. In this case, interestingly, the response of the disk is directly related to the type of wind. In other words, in some cases, the wind can stabilize the disk. On the other hand, in some cases it can destabilize the disk. We find that in some thin disk models where the magnetic pressure cannot explain the stability of the disk by including a typical contribution for magnetic pressure, wind can provide a viable explanation for the thermal stability.

Keywords: Stellar accretion disks, Stellar winds, Magnetic fields
Multiple Temperature Components of the Hot Circumgalactic Medium of the Milky Way. We present a deep XMM-Newton observation of the Galactic halo emission in the direction of the blazar 1ES 1553+113. In order to extract the Galactic halo component from the diffuse soft X-ray emission spectrum, accurately modeling the foreground components is crucial. Here we present complex modeling of the foregrounds with unprecedented details. A careful analysis of the spectrum yields two-temperature components of the halo gas ({T}1em} = {10}6.25-6.42 K, {T}2em}={10}6.68-6.92 K). We find that these temperatures obtained from the emission spectrum are not consistent with those from the absorption spectrum ({T}1ab}={10}6.07-6.13 K, {T}2ab}={10}6.96-7.15 K), unlike the previous studies that found only one-temperature component of the Milky Way circumgalactic medium. This provides us with interesting insights into the nature of emitting and absorbing systems. We discuss several possibilities objectively, and conclude that most likely we are observing multiple (3-4) discrete temperatures between {10}5.5 {{K}} and ≥slant {10}7 K in the Milky Way circumgalactic medium.

Keywords: X-ray astronomy, Hot ionized medium, Circumgalactic medium, Galaxy evolution, Milky Way evolution, Diffuse x-ray background, Warm-hot intergalactic medium, Milky Way Galaxy
A Comparison between Faraday Tomography and Synchrotron Polarization Gradients. Observations of synchrotron polarization at multiple frequencies in the presence of Faraday rotation can provide a way to reconstruct the 3D magnetic field distribution. In this paper we compare the well known Faraday Tomography (FT) technique to a new approach, Synchrotron Polarization Gradients (SPGs). We compare the strengths and limitations of the two techniques, and describe their synergy. In particular, we show that in situations when the FT technique fails, e.g., due to insufficient frequency coverage, the SPG can still trace the 3D structure of a magnetic field.

Keywords: Magnetohydrodynamics, Interstellar magnetic fields, Computational methods, Interstellar synchrotron emission, Interstellar medium
Globular Cluster Systems and X-Ray Atmospheres in Galaxies. We compare the empirical relationships between the mass of a galaxy’s globular cluster system (GCS) M GCS, the gas mass in the hot X-ray atmosphere M  X  within a fiducial radius of 5r  e , the total gravitational mass M grav within 5r  e , and lastly the total halo mass M  h  calibrated from weak lensing. We use a sample of 45 early-type galaxies for which both GCS and X-ray data are available; all the galaxies in our sample are relatively high-mass with M  h  &gt; 1012 M ⊙. We find that {M}X\propto {M}h1.0, similar to the previously known scaling relation {M}GCS}\propto {M}h1.0. Both components scale much more steeply than the more well known dependence of total stellar mass {M}\star \propto {M}h0.3 for luminous galaxies. These results strengthen previous suggestions that feedback had little effect on formation of the GCS. The current data are also used to measure the relative mass fractions of baryonic matter and dark matter within 5r  e . We find a strikingly uniform mean of &lt; {f}DM}&gt; =0.83 with few outliers and an rms scatter of ±0.07. This result is in good agreement with two recent suites of hydrodynamic galaxy formation models. Released on 2018 January 8th.

Keywords: Globular star clusters, Galaxy masses, X-ray sources
New Insights on the Collisional Depolarization of the Second Solar Spectrum of the Sr I 4607 Å Line. The spectrum of the linear polarization generated by scattering of anisotropic radiation near to the limb is called second solar spectrum (SSS). Our purpose is to present a new approach that allows accurate determination of the collisional depolarization rate D 2 of the SSS of the Sr I 4607 Å line. Most of the inaccuracy in determining the depolarization rate arises from errors in obtaining the interaction potential between the Sr I and H I atoms. To improve the accuracy of the depolarization rate, we determine hybrid potentials based on (1) ab initio quantum chemistry potentials for small interatomic distances; (2) Rayleigh-Schrödinger-Unsöld (RSU) potentials for large interatomic distances; and (3) joining the RSU and ab initio potentials by reasonably accurate interpolation to describe the interaction in the intermediate interatomic distances. The obtained hybrid potentials are used to infer new accurate hybrid depolarization rate for solar applications. Interestingly, we show that values of the hybrid rates are remarkably stable under the variation of the methods employed to compute hybrid potentials. Expected percentage of imprecision on the solar magnetic value resulting from a hypothetical inaccuracy in the D 2 is evaluated.

Keywords: Solar physics
Exomoons in the Habitable Zones of M Dwarfs. M dwarfs host most of the exoplanets in the local Milky Way. Some of these planets, ranging from sub-Earths to super-Jupiters, orbit in their stars’ habitable zones (HZs), although many likely possess surface environments that preclude habitability. Moreover, exomoons around these planets could harbor life for long timescales and thus may also be targets for biosignature surveys. Here we investigate the potential habitability, stability, and detectability of exomoons around exoplanets orbiting M dwarfs. We first compile an updated list of known M-dwarf exoplanet hosts, comprising 109 stars and 205 planets. For each M dwarf, we compute and update precise luminosities with the Virtual Observatory spectral energy distribution Analyzer and Gaia DR2 parallaxes to determine inner and outer boundaries of their HZs. For each planet, we retrieve (or, when necessary, homogeneously estimate) their masses and radii, calculate the long-term dynamical stability of hypothetical moons, and identify those planets that can support habitable moons. We find that 33 exoplanet candidates are located in the HZs of their host stars and that four of them could host Moon- to Titan-mass exomoons for timescales longer than the Hubble time.

Keywords: Late-type dwarf stars, Astrobiology, Exoplanet systems, Dynamical evolution
Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371. We studied a flare onset process in terms of stability of a three-dimensional (3D) magnetic field in active region 12371 producing an eruptive M6.5 flare in 2015 June 22. In order to reveal the 3D magnetic structure, we first extrapolated the 3D coronal magnetic fields based on time series of the photospheric vector magnetic fields under a nonlinear force-free field (NLFFF) approximation. The NLFFFs nicely reproduced the observed sigmoidal structure which is widely considered to be preeruptive magnetic configuration. In particular, we found that the sigmoid is composed of two branches of sheared arcade loops. On the basis of the NLFFFs, we investigated the sheared arcade loops to explore the onset process of the eruptive flare using three representative magnetohydrodynamic instabilities: the kink, torus, and double arc instabilities (DAI). The DAI, recently proposed by Ishiguro &amp; Kusano, is a double arc loop that can be more easily destabilized than a torus loop. Consequently, the NLFFFs are found to be quite stable against the kink and torus instabilities. However, the sheared arcade loops formed prior to the flare possibly become unstable against the DAI. As a possible scenario for the onset process of the M6.5 flare, we suggest a three-step process: (1) double arc loops are formed by the sheared arcade loops through the tether-cutting reconnection during an early phase of the flare, (2) the DAI contributes to the expansion of destabilized double arc loops, and (3) finally, the torus instability makes the full eruption.

Keywords: Solar coronal mass ejections
The Impact of the Dynamical State of Galaxy Groups on the Stellar Populations of Central Galaxies. We study the stellar populations of the brightest group galaxies (BGGs) in groups with different dynamical states, using Galaxy And Mass Assembly survey data. We use two independent, luminosity-dependent indicators to probe the relaxedness of their groups: the magnitude gap between the two most luminous galaxies (ΔM 12), and the offset between BGGs and the luminosity center (D offset) of the group. Combined, these two indicators were previously found useful for identifying relaxed and unrelaxed groups. We find that the BGGs of unrelaxed groups have significantly bluer near-ultraviolet-r colors than in relaxed groups. This is also true at the fixed sersic index. We find the bluer colors cannot be explained away by differing dust fraction, suggesting there are real differences in their stellar populations. Star formation rates derived from spectral energy distribution (SED) fitting tend to be higher in unrelaxed systems. This is in part because of a greater fraction of BGGs with non-elliptical morphology, but also because unrelaxed systems have larger numbers of mergers, some of which may bring fuel for star formation. The SED-fitted stellar metallicities of BGGs in unrelaxed systems also tend to be higher by around 0.05 dex, perhaps because their building blocks were more massive. We find that the ΔM 12 parameter is the most important parameter behind the observed differences in the relaxed/unrelaxed groups, in contrast with the previous study of Trevisan et al. We also find that groups selected to be unrelaxed using our criteria tend to have higher velocity offsets between the BGG and their group.

Keywords: Stellar populations, Galaxy colors, Galaxy structure, Galaxy classification systems, Galaxy evolution, Galaxy groups
Nonlinear Reconstruction of the Velocity Field. We propose a new velocity reconstruction method based on the displacement estimation of recently developed methods. The velocity is first reconstructed by transfer functions in Lagrangian space and then mapped into Eulerian space. High-resolution simulations are used to test the performance. We find that the new reconstruction method outperforms the standard velocity reconstruction in the sense of better cross-correlation coefficient, less velocity misalignment, and smaller amplitude difference. We conclude that this new method has the potential to improve large-scale structure sciences involving velocity reconstruction, such as kinetic Sunyaev-Zel’dovich measurement and supernova cosmology.

Keywords: Cosmology, Large-scale structure of the universe
X-shaped Radio Galaxies: Optical Properties, Large-scale Environment, and Relationship to Radio Structure. In pursuit of clues to the origin of “winged” or X-shaped radio galaxies (XRGs) we investigate the parent galaxies of a large sample of 106 XRGs for optical-radio axes alignment, interstellar medium, black hole mass, and large-scale environment. For 41 of the XRGs it was possible to determine the optical major axis and the primary radio axis and the strong tendency for the two axes to be fairly close is confirmed. However, several counter-examples were also found and these could challenge the widely discussed backflow diversion model for the origin of the radio wings. Comparison with a well-defined large sample of normal FR II radio galaxies has revealed that: (i) XRGs possess slightly less massive central black holes than the normal radio galaxies (average masses being logM BH ∼ 8.81 M ⊙ and 9.07 M ⊙, respectively); (ii) a much higher fraction of XRGs (∼80%) exhibits red mid-IR colors (W2 - W3 &gt; 1.5), indicating a population of young stars and/or an enhanced dust mass, probably due to relatively recent galaxy merger(s). A comparison of the large-scale environment (i.e., within ∼1 Mpc) shows that both XRGs and FRII radio galaxies inhabit similarly poor galaxy clustering environments (medium richness being 8.94 and 11.87, respectively). Overall, the origin of XRGs seems difficult to reconcile with a single dominant physical mechanism and competing mechanisms seem prevalent.

Keywords: Supermassive black holes, Radio jets, Active galaxies, Radio galaxies, Active galactic nuclei