Sazuna/UAT_keywords huggingface dataset:
Microinstabilities in the Transition Region of Weak Quasi-perpendicular Intracluster Shocks. Microinstabilities play important roles in both entropy generation and particle acceleration in collisionless shocks. Recent studies have suggested that in the transition region of quasi-perpendicular (Q⊥) shocks in the high-beta (β = Pgas/PB) intracluster medium (ICM), the ion temperature anisotropy due to the reflected-gyrating ions could trigger the Alfvén ion cyclotron (AIC) instability and the ion-mirror instability, while the electron temperature anisotropy induced by magnetic field compression could excite the whistler instability and the electron-mirror instability. Adopting the numerical estimates for ion and electron temperature anisotropies found in the particle-in-cell (PIC) simulations of Q⊥ shocks with sonic Mach numbers, Ms = 2-3, we carry out a linear stability analysis for these microinstabilities. The kinetic properties of the microinstabilities and the ensuing plasma waves on both ion and electron scales are described for wide ranges of parameters, including β and the ion-to-electron mass ratio. In addition, the nonlinear evolution of the induced plasma waves are examined by performing 2D PIC simulations with periodic boundary conditions. We find that for β ≈ 20-100, the AIC instability could induce ion-scale waves and generate shock surface ripples in supercritical shocks above the AIC critical Mach number, ${M}_{\mathrm{AIC}}^{* }\approx 2.3$ . Also, electron-scale waves are generated primarily by the whistler instability in these high-β shocks. The resulting multiscale waves from electron to ion scales are thought to be essential in the electron injection to diffusive shock acceleration in Q⊥ shocks in the ICM.

Keywords: Shocks, Plasma astrophysics
Morphological Types of DM Halos in Milky Way-like Galaxies in the TNG50 Simulation: Simple, Twisted, or Stretched. We present a comprehensive analysis of the shape of dark matter (DM) halos in a sample of 25 Milky Way-like galaxies in TNG50 simulation. Using an enclosed volume iterative method, we infer an oblate-to-triaxial shape for the DM halo with median T ≃ 0.24. We group DM halos into three different categories. Simple halos (32% of the population) establish principal axes whose ordering in magnitude does not change with radius and whose orientations are almost fixed throughout the halo. Twisted halos (32%) experience levels of gradual rotations throughout their radial profiles. Finally, stretched halos (36%) demonstrate a stretching in the lengths of their principal axes where the ordering of different eigenvalues changes with radius. Subsequently, the halo experiences a "rotation" of ∼90° where the stretching occurs. Visualizing the 3D ellipsoid of each halo, for the first time, we report signs of a reorienting ellipsoid in twisted and stretched halos. We examine the impact of baryonic physics on DM halo shape through a comparison to dark matter only (DMO) simulations. This suggests a triaxial (prolate) halo. We analyze the impacts of substructure on DM halo shape in both hydrodynamical and DMO simulations and confirm that they are subdominant. We study the distribution of satellites in our sample. In simple and twisted halos, the angle between satellites' angular momentum and the galaxy's angular momentum grows with radius. However, stretched halos show a flat distribution of angles. Overlaying our theoretical outcome on the observational results presented in the literature establishes a fair agreement.

Keywords: Hydrodynamical simulations, Cold dark matter, Milky Way Galaxy, Galaxy classification systems
Revisiting Attenuation Curves: The Case of NGC 3351. Multiwavelength images from the far-UV (∼0.15 μm) to the submillimeter of the central region of the galaxy NGC 3351 are analyzed to constrain its stellar populations and dust attenuation. Despite hosting a ∼1 kpc circumnuclear starburst ring, NGC 3351 deviates from the IRX-β relation, the relation between the infrared-to-UV luminosity ratio and the UV continuum slope β that other starburst galaxies follow. To understand the reason for the deviation, we leverage the high angular resolution of archival near-UV-to-near-IR Hubble Space Telescope images to divide the ring into ∼60-180 pc size regions and model each individually. We find that the UV slope of the combined intrinsic (dust-free) stellar populations in the central region is redder than what is expected for a young model population. This is due to the region's complex star formation history, which boosts the near-UV emission relative to the far-UV. The resulting net attenuation curve has a UV slope that lies between those of the starburst attenuation curve (Calzetti et al. 2000) and the Small Magellanic Cloud extinction curve; the total-to-selective attenuation value, $R^{\prime} $ (V) = 4.93, is larger than both. As found for other star-forming galaxies, the stellar continuum of NGC 3351 is less attenuated than the ionized gas, with E(B - V)star = 0.40 E(B - V)gas. The combination of the "red" intrinsic stellar population and the new attenuation curve fully accounts for the location of the central region of NGC 3351 on the IRX-β diagram. Thus, the observed characteristics result from the complex mixture of stellar populations and dust column densities in the circumnuclear region. Despite being a sample of one, these findings highlight the difficulty of defining attenuation curves of general applicability outside the regime of centrally concentrated starbursts. * Based on observations obtained with the NASA/ESA Hubble Space Telescope, at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: Reddening law, Starburst galaxies, Interstellar extinction
The Influence of Metallicity on the Leavitt Law from Geometrical Distances of Milky Way and Magellanic Cloud Cepheids. The Cepheid period-luminosity (PL) relation is the key tool for measuring astronomical distances and for establishing the extragalactic distance scale. In particular, the local value of the Hubble constant (H0) strongly depends on Cepheid distance measurements. The recent Gaia Data Releases and other parallax measurements from the Hubble Space Telescope (HST) already enabled us to improve the accuracy of the slope (α) and intercept (β) of the PL relation. However, the dependence of this law on metallicity is still largely debated. In this paper, we combine three samples of Cepheids in the Milky Way (MW), the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC) in order to derive the metallicity term (hereafter γ) of the PL relation. The recent publication of extremely precise LMC and SMC distances based on late-type detached eclipsing binary systems provides a solid anchor for the Magellanic Clouds. In the MW, we adopt Cepheid parallaxes from the early third Gaia Data Release. We derive the metallicity effect in V, I, J, H, KS, WVI, and WJK. In the KS band we report a metallicity effect of -0.221 ± 0.051 mag dex-1, the negative sign meaning that more metal-rich Cepheids are intrinsically brighter than their more metal-poor counterparts of the same pulsation period.

Keywords: Metallicity, Parallax, Cepheid distance, Magellanic Clouds, Milky Way Galaxy
Chemodynamically Characterizing the Jhelum Stellar Stream with APOGEE-2. We present the kinematic and chemical profiles of red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE)-2 survey in the direction of the Jhelum stellar stream, a Milky Way substructure located in the inner halo of the Milky Way at a distance from the Sun of ≈13 kpc. From the six APOGEE-2 Jhelum pointings, we isolate stars with log(g) &lt; 3.5, leaving a sample of 289 red giant stars. From this sample of APOGEE-2 giants, we identified seven stars that are consistent with the astrometric signal from Gaia DR2 for this stream. Of these seven, one falls onto the red giant branch (RGB) along the same sequence as the Jhelum stars presented by Ji et al. This new Jhelum member has [Fe/H] = -2.2 and is at the tip of the RGB. By selecting high orbital eccentricity, metal-rich stars, we identify red giants in our APOGEE2 sample that are likely associated with the Gaia-Enceladus-Sausage (GES) merger. We compare the abundance profiles of the Jhelum stars and GES stars and find similar trends in α-elements, as expected for low-metallicity populations. However, we find that the orbits for GES and Jhelum stars are not generally consistent with a shared origin. The chemical abundances for the APOGEE-2 Jhelum star and other confirmed members of the stream are similar to stars in known stellar streams and thus are consistent with an accreted dwarf galaxy origin for the progenitor of the stream, although we cannot rule out a globular cluster origin.

Keywords: Stellar streams
Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs Using Differential Emission Measure Polynomials. Characterizing the atmospheres of planets orbiting M dwarfs requires understanding the spectral energy distributions of M dwarfs over planetary lifetimes. Surveys like MUSCLES, HAZMAT, and FUMES have collected multiwavelength spectra across the spectral type's range of Teff and activity, but the extreme ultraviolet (EUV, 100-912 Å) flux of most of these stars remains unobserved because of obscuration by the interstellar medium compounded with limited detector sensitivity. While targets with observable EUV flux exist, there is no currently operational facility observing between 150 and 912 Å. Inferring the spectra of exoplanet hosts in this regime is critical to studying the evolution of planetary atmospheres because the EUV heats the top of the thermosphere and drives atmospheric escape. This paper presents our implementation of the differential emission measure technique to reconstruct the EUV spectra of cool dwarfs. We characterize our method's accuracy and precision by applying it to the Sun and AU Mic. We then apply it to three fainter M dwarfs: GJ 832, Barnard's star, and TRAPPIST-1. We demonstrate that with the strongest far-ultraviolet (FUV, 912-1700 Å) emission lines, observed with the Hubble Space Telescope and/or Far Ultraviolet Spectroscopic Explorer, and a coarse X-ray spectrum from either the Chandra X-ray Observatory or XMM-Newton, we can reconstruct the Sun's EUV spectrum to within a factor of 1.8, with our model's formal uncertainties encompassing the data. We report the integrated EUV flux of our M dwarf sample with uncertainties of a factor of 2-7 depending on available data quality.

Keywords: M dwarf stars, Solar extreme ultraviolet emission, Stellar chromospheres, Stellar activity, Ultraviolet astronomy, Low mass stars, Stellar coronae, Stellar atmospheres
Dense and Warm Neutral Gas in BR 1202-0725 at z = 4.7 as Traced by the [O I] 145 μm Line. We report the detection of [O I] 145.5 μm in the BR 1202-0725 system, a compact group at z = 4.7 consisting of a quasar (QSO), a submillimeter-bright galaxy (SMG), and three faint Lyα emitters. By taking into account the previous detections and upper limits, the [O I] /[C II] line ratios of the now five known high-z galaxies are higher than or on the high end of the observed values in local galaxies ([O I] /[C II] ≳ 0.13). The high [O I] /[C II] ratios and the joint analysis with previous detection of [N II] lines for both of the QSO and the SMG suggest the presence of warm and dense neutral gas in these highly star-forming galaxies. This is further supported by new CO (12-11) line detections and a comparison with cosmological simulations. There is a possible positive correlation between the [N II] 122/205 line ratio and the [O I] /[C II] ratio when all local and high-z sources are taken into account, indicating that the denser the ionized gas, the denser and warmer the neutral gas (or vice versa). The detection of the [O I] line in the BR 1202-0725 system with a relatively short amount of integration with Atacama Large Millimeter/submillimeter Array (ALMA) demonstrates the great potential of this line as a dense gas tracer for high-z galaxies.

Keywords: Starburst galaxies, Interstellar line emission, Quasars, Galaxy evolution, Submillimeter astronomy
Black Hole Mass Function of Coalescing Binary Black Hole Systems: Is there a Pulsational Pair-instability Mass Cutoff?. We analyze the LIGO/Virgo GWTC-2 catalog to study the primary mass distribution of the merging black holes. We perform hierarchical Bayesian analysis and examine whether the mass distribution has a sharp cutoff for primary black hole masses below 65 M⊙, as predicted in the pulsational pair-instability supernova model. We construct two empirical mass functions. One is a piece-wise function with two power-law segments joined by a sudden drop. The other consists of a main-truncated power-law component, a Gaussian component, and a third very massive component. Both models can reasonably fit the data and a sharp drop of the mass distribution is found at ∼50M⊙, suggesting that the majority of the observed black holes can be explained by the stellar evolution scenarios in which the pulsational pair-instability process takes place. On the other hand, the very massive subpopulation, which accounts for at most several percent of the total, may be formed through hierarchical mergers or other processes.

Keywords: Intermediate-mass black holes, Bayesian statistics, Hierarchical models, Astrophysical black holes
Evidence for an MHD Disk Wind via Optical Forbidden Line Spectroastrometry. Spectroastrometry is used to investigate the low-velocity component (LVC) of the optical forbidden emission from the T Tauri stars RU Lupi and AS 205 N. Both stars also have high-velocity forbidden emission, which is tracing a jet. For AS 205 N, analysis reveals a complicated outflow system. For RU Lupi, the [O I] λ6300 and [S II]λλ6716,6731 LV narrow component (NC) is offset along the same position angle (PA) as the high-velocity component but with a different velocity gradient than the jet, in that displacement from the stellar position along the rotation axis is decreasing with increasing velocity. From the LVC, NC, PA, and velocity gradient, it is inferred that the NC is tracing a wide-angled magnetohydrodynamic (MHD) disk wind. A photoevaporative wind is ruled out. This is supported by a comparison with a previous spectroastrometric study of the CO fundamental line. The decrease in offset with increasing velocity is interpreted as tracing an increase in the height of the wind with increasing disk radius. This is one of the first measurements of the spatial extent of the forbidden emission line LVC NC (∼40 au, 8 au for RU Lupi in the [S II] λ6731 and [O I] λ6300 lines) and the first direct confirmation that the LVC narrow component can trace an MHD disk wind. * Based on data collected by UVES (089.C-0299(A), 089.C-0299(B), P.I. I. Pascucci) observations at the VLT on Cerro Paranal (Chile) which is operated by the European Southern Observatory (ESO).

Keywords: Stellar accretion disks, Stellar jets, Interstellar medium wind, Star formation
Searching for Local Counterparts of High-redshift Poststarburst Galaxies in Integral Field Unit Spectroscopic Surveys of Nearby Galaxies. Searching in the MaNGA IFU survey, I identify nine galaxies that have strong Balmer absorption lines and weak nebular emission lines measured from the spectra integrated over the entire IFU. The spectral features measured from the bulk of the stellar light make these galaxies local analogs of high-redshift spectroscopically selected poststarburst galaxies and thus proxies to understand the mechanisms producing poststarburst galaxies at high redshifts. I present the distributions of absorption line indices and emission line strengths, as well as the stellar kinematics of these local poststarburst galaxies. Almost all local poststarburst galaxies have central compact emission line regions at the central &lt;1 kpc, mostly powered by weak star formation activities. The age-sensitive absorption line indices EW(Hδ) and Dn4000 indicate that the stellar populations at the outskirts are older. Toy stellar population synthesis models suggest that the galaxies as a whole are experiencing a rapid decline of star formation with residual star formation activities at the centers. These features indicate that most poststarburst galaxies are the aftermath of highly dissipative processes that drive gas into centers, invoke centrally concentrated star formation, and then quench the galaxies. Meanwhile, when measurable, poststarburst galaxies have the directions of maximum stellar velocity gradients aligned with photometric major axes, which suggest against major mergers being the principal driving mechanism, while gas-rich minor mergers are plausible. While directly obtaining the same quality of spatially resolved spectra of high-redshift poststarburst galaxies is very difficult, finding proper local counterparts provides an alternative to understand quenching processes in the distant universe.

Keywords: Optical astronomy, Galaxy stellar content, Galaxy ages, Galaxy quenching, Post-starburst galaxies
Star Formation Histories from Spectral Energy Distributions and Color-magnitude Diagrams Agree: Evidence for Synchronized Star Formation in Local Volume Dwarf Galaxies over the Past 3 Gyr. Star formation histories (SFHs) reveal physical processes that influence how galaxies form their stellar mass. We compare the SFHs of a sample of 36 nearby (D ⪅ 4 Mpc) dwarf galaxies from the ACS Nearby Galaxy Survey Treasury (ANGST), inferred from the color-magnitude diagrams (CMDs) of individually resolved stars in these galaxies, with those reconstructed by broadband spectral energy distribution (SED) fitting using the dense basis SED-fitting code. When comparing individual SFHs, we introduce metrics for evaluating SFH reconstruction techniques. For both the SED and CMD methods, the median normalized SFH of galaxies in the sample shows a period of quiescence at lookback times of 3-6 Gyr followed by rejuvenated star formation over the past 3 Gyr that remains active until the present day. To determine if these represent special epochs of star formation in the D &lt;4 Mpc portion of the Local Volume, we break this ANGST dwarf galaxy sample into subsets based on specific star formation rate and spatial location. Modulo offsets between the methods of about 1 Gyr, all subsets show significant decreases and increases in their median normalized SFHs at the same epochs, and the majority of the individual galaxy SFHs are consistent with these trends. These results motivate further study of potential synchronized star formation quiescence and rejuvenation in the Local Volume as well as development of a hybrid method of SFH reconstruction that combines CMDs and SEDs, which have complementary systematics.

Keywords: Dwarf galaxies, Star formation, Spectral energy distribution, Galaxy evolution, Galaxies
Competitive Dehydrogenation and Backbone Fragmentation of Superhydrogenated PAHs: A Laboratory Study. Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) have been suggested to catalyze the formation of H2 in certain regions of space, but it remains unclear under which circumstances this mechanism is viable given the reduced carbon backbone stability of superhydrogenated PAHs. We report a laboratory study on the stability of the smallest pericondensed PAH, pyrene (C16H10+N, with N = 4, 6, and 16 additional H atoms), against photodestruction by single vacuum ultraviolet photons using the photoelectron-photoion coincidence technique. For N = 4, we observe a protective effect of hydrogenation against the loss of native hydrogens, in the form of an increase in the appearance energies of the ${{\rm{C}}}_{16}{{\rm{H}}}_{9}^{+}$ and C16H8+ daughter ions compared to those reported for pristine pyrene (C16H10). No such effect is seen for N = 6 or 16, where the weakening effect of replacing aromatic bonds with aliphatic ones outweighs the buffering effect of the additional hydrogen atoms. The onset of fragmentation occurs at similar internal energies for N = 4 and 6, but is significantly lower for N = 16. In all three cases, H-loss and CmHn-loss (m ≥ 1, carbon backbone fragmentation) channels open at approximately the same energy. The branching fractions of the primary channels favor H-loss for N = 4, CmHn-loss for N = 16, and are roughly equal for the intermediate N = 6. We conclude that superhydrogenated pyrene is probably too small to support catalytic H2-formation, while trends in the current and previously reported data suggest that larger PAHs may serve as catalysts up to a certain level of hydrogenation.

Keywords: Reaction catalysts, Polycyclic aromatic hydrocarbons, Laboratory astrophysics, Photodissociation regions, Astrochemistry
Magnetofrictional Modeling of an Erupting Pseudostreamer. In this study, we present the magnetic configuration of an erupting pseudostreamer observed on 2015 April 19, on the southwest limb of the Sun, with a prominence cavity embedded inside. The eruption resulted in a partial halo coronal mass ejection. The prominence eruption begins with a slow rise and then evolves to a fast-rise phase. We analyze this erupting pseudostreamer using the flux-rope insertion method and magnetofrictional relaxation to establish a sequence of plausible out-of-equilibrium magnetic configurations. This approach allows the direct incorporation of observations of structures seen in the corona (filament and cavity) to appropriately model the pseudostreamer based on SDO/HMI line-of-sight photospheric magnetograms. We also perform a topological analysis in order to determine the location of quasiseparatrix layers (QSLs) in the models, producing Q-maps to examine how the QSL locations progress in the higher iterations. We found that the axial flux in our best-fit unstable model was a factor of 20 times higher than we found in our marginally stable case. We computed the average magnetic field strength of the prominence and found that the unstable model exhibits twice the average field strength of the stable model. The eruption height from our modeling matches very well with the prominence eruption height measured from the AIA observation. The Q-maps derived from the model reproduce structures observed in LASCO/C2. Thus, the modeling and topological analysis results are fully consistent with the observed morphological features, implying that we have captured the large magnetic structure of the erupting filament in our magnetofrictional simulation.

Keywords: Solar corona
Optical Analysis and Modeling of HD96670, a New Black Hole X-Ray Binary Candidate. We report on optical observations and modeling of HD96670, a single-line spectroscopic binary in the Carina OB2 association. We collected 10 epochs of optical spectroscopy, and optical photometry on 17 nonconsecutive nights on the source. We construct a radial velocity curve from the spectra, and update the orbital period of the binary to be P = 5.28388 ± 0.00046 days. The spectra show oxygen and helium absorption, consistent with an O-type primary. We see no evidence for spectral lines from the secondary star in the binary. We model the optical light curve and radial velocity curve simultaneously using the Wilson-Devinney code and find a best-fit mass of ${M}_{1}={22.7}_{-3.6}^{+5.2}\,{M}_{\odot }$ for the primary, and ${M}_{2}={6.2}_{-0.7}^{+0.9}\,{M}_{\odot }$ for the secondary. An object of this mass is consistent with either a B-type star, or a black hole. Given that we see no absorption lines from the secondary, in combination with an observed hard power-law X-ray spectrum with Γ = 2.6 detected past 10 keV that may have been produced by wind accretion onto the secondary, we conclude that the secondary is most likely a black hole. We see asymmetrical helium lines with a shape consistent with the presence of a third star. If the secondary is indeed a black hole, this system would add to the small sample of only four possible black hole high mass X-ray binaries in the galaxy.

Keywords: X-ray binary stars, High mass x-ray binary stars