Sazuna/UAT_keywords huggingface dataset:
In Situ Heating of the Nightside Martian Upper Atmosphere and Ionosphere: The Role of Solar Wind Electron Precipitation. In the absence of solar radiation, precipitating electrons from the solar wind (SW) are generally thought to be the dominant source of energy deposition in the nightside Martian upper atmosphere, creating a patchy ionosphere and possibly also affecting the nightside thermal budget of various neutral and ionized species. Previous model calculations have not taken into account in situ heating via SW electron impact. In the present study, we utilize extensive measurements made by several instruments on board the Mars Atmosphere and Volatile Evolution spacecraft, in order to perform data-driven computations of the nightside neutral, ion, and electron heating rates. Considering the large range of energetic electron intensity observed on the nightside of Mars, we divide the entire data set into two subsamples, either with or without energetic electron depletion, a notable feature of the nightside Martian ionosphere. Our calculations indicate that in situ nightside neutral heating is dominated by exothermic chemistry and Maxwell interaction with thermal ions for regions with depletion, and by direct SW impact for regions without. Collisional quenching of excited state species produced from a variety of channels, such as electron impact excitation, dissociation, and ionization, as well as ${{\rm{O}}}_{2}^{+}$ dissociative recombination, makes a substantial contribution to neutral heating, except during depletion. For comparison, nightside ion heating is mainly driven by energetic ion production under all circumstances, which occurs mainly via ion-neutral reaction O+ + CO2 and CO2+ predissociation.

Keywords: Mars, Planetary atmospheres
Photoevaporative Dispersal of Protoplanetary Disks around Evolving Intermediate-mass Stars. We aim to understand the effect of stellar evolution on the evolution of protoplanetary disks. We focus in particular on the disk evolution around intermediate-mass (IM) stars, which evolve more rapidly than low-mass ones. We numerically solve the long-term evolution of disks around 0.5-5 M⊙ stars considering viscous accretion and photoevaporation (PE) driven by stellar far-ultraviolet (FUV), extreme-ultraviolet (EUV), and X-ray emission. We also take stellar evolution into account and consider the time evolution of the PE rate. We find that the FUV, EUV, and X-ray luminosities of IM stars evolve by orders of magnitude within a few million years, along with the time evolution of stellar structure, stellar effective temperature, or accretion rate. Therefore, the PE rate also evolves with time by orders of magnitude, and we conclude that stellar evolution is crucial for the disk evolution around IM stars.

Keywords: Pre-main sequence stars, Protoplanetary disks, Planet formation, Stellar evolution
Statistical Survey of Reservoir Phenomenon in Energetic Proton Events Observed by Multiple Spacecraft. In this work, reservoir phenomenon in the decay phase of gradual solar energetic particle (SEP) events are investigated with two Helios and the IMP 8 spacecraft from 1976 January to 1980 March and two STEREO and the SOHO spacecraft from 2010 January to 2014 September. Using these data, 62 reservoir events of solar energetic protons were identified, and the effects of perpendicular diffusion and magnetic mirroring on the formation of the reservoir phenomenon have been studied. We find that the reservoir events could be observed in almost all longitudes in the ecliptic at 1 au; thus, the perpendicular diffusion in interplanetary space is an important mechanism to explain the uniform distribution of SEPs. Furthermore, in the 1976 April 30 event, the effects of magnetic mirroring associated with an interplanetary coronal mass ejection were observed during the reservoir phenomenon. Therefore, the effects of magnetic mirroring could also help to form the reservoir phenomenon. This study could improve the understanding of the propagation of SEPs in interplanetary space.

Keywords: Solar flares, Solar energetic particles, Interplanetary particle acceleration, Solar coronal mass ejections, Solar particle emission
Review of the Particle Background of the Athena X-IFU Instrument. X-ray observations are limited by the background, due to the intrinsic faintness or diffuse nature of the sources. The future Athena X-ray observatory has among its goals the characterization of these sources. We aim at characterizing the particle-induced background of the Athena microcalorimeter, in both its low- (soft protons) and high-energy (galactic cosmic rays—GCR) induced components, to assess the instrument capability to characterize background-dominated sources such as the outskirts of clusters of galaxies. We compare two radiation environments, namely the L1 and L2 Lagrangian points, and derive indications against the latter. We estimate the particle-induced background level on the X-IFU microcalorimeter with Monte Carlo simulations, before and after all of the solutions adopted to reduce its level. Concerning the GCR-induced component, the background level is compliant with the mission requirement. Regarding the soft-proton component, the analysis does not predict dramatically different backgrounds in the L1 and L2 orbits. However, the lack of data concerning the L2 environment labels it as very weakly characterizable, and thus we advise against choosing it as the orbit for X-ray missions. We then use these background levels to simulate the observation of a typical galaxy cluster from its center out to 1.2 R200 to probe the characterization capabilities of the instrument out to the outskirts. We find that without any background reduction, it is not possible to characterize the properties of the cluster in the outer regions. We also find no improvement in the observations when carried out during the solar maximum with respect to solar minimum conditions.

Keywords: X-ray astronomy, Galaxy clusters, X-ray telescopes, Computational methods, Astronomical instrumentation, Intracluster medium
Flybys, Orbits, Splashback: Subhalos and the Importance of the Halo Boundary. The classification of dark matter halos as isolated hosts or subhalos is critical for our understanding of structure formation and the galaxy-halo connection. Most commonly, subhalos are defined to reside inside a spherical overdensity boundary such as the virial radius. The resulting host-subhalo relations depend sensitively on the somewhat arbitrary overdensity threshold, but the impact of this dependence is rarely quantified. The recently proposed splashback radius tends to be larger and to include more subhalos than even the largest spherical overdensity boundaries. We systematically investigate the dependence of the subhalo fraction on the radius definition and show that it can vary by factors of unity between different spherical overdensity definitions. Using splashback radii can yet double the abundance of subhalos compared to the virial definition. We also quantify the abundance of flyby (or backsplash) halos, hosts that used to be subhalos in the past. We show that the majority of these objects are mislabeled satellites that are naturally classified as subhalos when we use the splashback radius. We show that the subhalo fraction can be understood as a universal function of only peak height and the slope of the linear power spectrum. We provide a simple fitting function that captures our simulation results to 20% accuracy across a wide range of halo masses, redshifts, and cosmologies. Finally, we demonstrate that splashback radii significantly change our understanding of satellite and flyby galaxies in the Local Group.

Keywords: Cold dark matter, Large-scale structure of the universe
Revealing Efficient Dust Formation at Low Metallicity in Extragalactic Carbon-rich Wolf-Rayet Binaries. We present Spitzer/InfraRed Array Camera observations of dust formation from six extragalactic carbon-rich Wolf-Rayet (WC) binary candidates in low-metallicity (Z ≲ 0.65 Z☉) environments using multiepoch mid-infrared (IR) imaging data from the SPitzer InfraRed Intensive Transients Survey (SPIRITS). Optical follow-up spectroscopy of SPIRITS 16ln, 19q, 16df, 18hb, and 14apu reveals emission features from C IV λ5801-12 and/or the C III-IV λ4650/He II λ4686 blend that are consistent with early-type WC stars. We identify SPIRITS 16ln as the variable mid-IR counterpart of the recently discovered colliding-wind WC4 + O binary candidate, N604-WRXc, located in the subsolar metallicity NGC 604 H II region in M33. We interpret the mid-IR variability from SPIRITS 16ln as a dust-formation episode in an eccentric colliding-wind WC binary. SPIRITS 19q, 16df, 14apu, and 18hb exhibit absolute [3.6] magnitudes exceeding that of one of the most IR-luminous dust-forming WC systems known, WR 104 (M[3.6] ≲ -12.3). An analysis of dust formation in the mid-IR outburst from SPIRITS 19q reveals a high dust production rate of ${\dot{M}}_{d}\gtrsim 2\times {10}^{-6}$ M☉ yr-1, which may therefore exceed that of the most efficient dust-forming WC systems known. We demonstrate that efficient dust formation is feasible from early-type WC binaries in the theoretical framework of colliding-wind binary dust formation if the systems host an O-type companion with high mass-loss rates ( $\dot{M}\gtrsim 1.6\times {10}^{-6}$ M☉ yr-1). This efficient dust formation from early-type WC binaries highlights their potential role as significant sources of dust in low-metallicity environments.

Keywords: WC stars, Infrared astronomy, Stellar winds, Time domain astronomy, Wolf-Rayet stars, Circumstellar dust
Afterglow Constraints on the Viewing Angle of Binary Neutron Star Mergers and Determination of the Hubble Constant. One of the key properties of any binary is its viewing angle (i.e., inclination), θobs. In binary neutron star (BNS) mergers it is of special importance due to the role that it plays in the measurement of the Hubble constant, H0. The opening angle of the jet that these mergers launch, θj, is also of special interest. Following the detection of the first BNS merger, GW170817, there were numerous attempts to estimate these angles using the afterglow light curve, finding a wide range of values. Here we provide a simple formula for the ratio θobs/θj based on the afterglow light curve and show that this is the only quantity that can be determined from the light curve alone. Our result explains the inconsistency of the values found by the various studies of GW170817 that were largely driven by the different priors taken in each study. Among the additional information that can be used to estimate θobs and θj, the most useful is a VLBI measurement of the afterglow image superluminal motion. An alternative is an identification of the afterglow transition to the subrelativistic phase. These observations are possible only for mergers observed at small viewing angles, whose afterglow is significantly brighter than the detector's threshold. We discuss the implications of these results to measurements of H0 using GW observations. We show that while the viewing angle will be measured only in a small fraction of future BNS mergers, it can significantly reduce the uncertainty in H0 in each one of these events, possibly to a level of 4%-5%.

Keywords: Hubble constant, Gamma-ray bursts, Gravitational waves, Gravitational wave astronomy
Planets Across Space and Time (PAST). I. Characterizing the Memberships of Galactic Components and Stellar Ages: Revisiting the Kinematic Methods and Applying to Planet Host Stars. Over 4000 exoplanets have been identified and thousands of candidates are to be confirmed. The relations between the characteristics of these planetary systems and the kinematics, Galactic components, and ages of their host stars have yet to be well explored. To address these questions, we conduct a research project, dubbed Planets Across Space and Time (PAST). To do this, one of the key steps is to accurately characterize the planet host stars. In this paper, Paper I of the PAST series, we revisit the kinematic method for classification of Galactic components and extend the applicable range of velocity ellipsoid from ∼100 pc to ∼1500 pc from the Sun in order to cover most known planet hosts. Furthermore, we revisit the age-velocity dispersion relation (AVR), which allows us to derive kinematic ages with a typical uncertainty of 10-20% for an ensemble of stars. Applying the above revised methods, we present a catalog of kinematic properties (i.e., Galactic positions, velocities, and the relative membership probabilities among the thin disk, thick disk, Hercules stream, and the halo) as well as other basic stellar parameters for 2174 host stars of 2872 planets by combining data from Gaia, LAMOST, APOGEE, RAVE, and the NASA exoplanet archive. The revised kinematic method and AVR, as well as the stellar catalog of kinematic properties and ages, lay the foundation for future studies of exoplanets in space and time in the Galactic context.

Keywords: Exoplanet catalogs, Stellar ages, Exoplanets, Stellar kinematics, Milky Way Galaxy
Environmental Dependence of Galactic Properties Traced by Lyα Forest Absorption: Diversity among Galaxy Populations. In order to shed light on how galactic properties depend on the intergalactic medium (IGM) environment traced by the Lyα forest, we observationally investigate the IGM-galaxy connection using the publicly available 3D IGM tomography data (CLAMATO) and several galaxy catalogs in the COSMOS field. We measure the cross-correlation function (CCF) for 570 galaxies with spec-z measurements and detect a correlation with the IGM up to 50 h-1 comoving Mpc. We show that galaxies with stellar masses of 109-1010 M☉ are the dominant contributor to the total CCF signal. We also investigate CCFs for several galaxy populations: Lyα emitters (LAEs), Hα emitters (HAEs), [O III] emitters (O3Es), active galactic nuclei (AGNs), and submillimeter galaxies (SMGs), and we detect the highest signal in AGNs and SMGs at large scales (r ≥ 5 h-1 Mpc), but in LAEs at small scales (r &lt; 5 h-1 Mpc). We find that they live in various IGM environments—HAEs trace the IGM in a similar manner to the continuum-selected galaxies, but LAEs and O3Es tend to reside in higher-density regions. Additionally, LAEs' CCF is flat up to r ∼ 3 h-1 Mpc, indicating that they tend to avoid the highest-density regions. For AGNs and SMGs, the CCF peak at r = 5-6 h-1 Mpc implies that they tend to be in locally lower-density regions. We suspect that it is due to the photoionization of IGM H I by AGNs, i.e., the proximity effect.

Keywords: AGN host galaxies, Galaxy formation, Large-scale structure of the universe, Lyman alpha forest, Emission line galaxies, Galaxy evolution, Intergalactic medium, Lyman-alpha galaxies
The Origin and Evolution of Lyα Blobs in Cosmological Galaxy Formation Simulations. High-redshift Lyα blobs (LABs) are an enigmatic class of objects that have been the subject of numerous observational and theoretical investigations. It is of particular interest to determine the dominant power sources for their luminosity, as direct emission from H II regions, cooling gas, and fluorescence due to the presence of active galactic nuclei (AGNs) can all contribute significantly. In this paper, we present the first theoretical model to consider all of these physical processes in an attempt to develop a model for the origin of LABs. This is achieved by combining a series of high-resolution cosmological zoom-in simulations with ionization and Lyα radiative transfer models. We find that massive galaxies display a range of Lyα luminosities and spatial extents (which strongly depend on the limiting surface brightness used) over the course of their lives, though regularly exhibit luminosities and sizes consistent with observed LABs. The model LABs are typically powered from a combination of recombination in star-forming galaxies, as well as cooling emission from gas associated with accretion. When AGNs are included in the model, the fluorescence caused by active galactic nucleus-driven ionization can be a significant contributor to the total Lyα luminosity as well. Within our modeled mass range, there are no obvious threshold physical properties that predict the appearance of LABs, and only weak correlations of the luminosity with the physical properties of the host galaxy. This is because the emergent Lyα luminosity from a system is a complex function of the gas temperature, ionization state, and Lyα escape fraction.

Keywords: Radiative transfer simulations, Galaxy formation, Galaxies
SDSS-IV MaNGA: The Radial Profile of Enhanced Star Formation in Close Galaxy Pairs. We compare the radial profiles of the specific star formation rate (sSFR) in a sample of 169 star-forming galaxies in close pairs with those of mass-matched control galaxies in the SDSS-IV MaNGA survey. We find that the sSFR is centrally enhanced (within one effective radius) in interacting galaxies by ∼0.3 dex and that there is a weak sSFR suppression in the outskirts of the galaxies of ∼0.1 dex. We stack the difference profiles for galaxies in five stellar-mass bins in the range log(M/M⊙) = 9.0-11.5 and find that the sSFR enhancement has no dependence on the stellar mass. The same result is obtained when comparison galaxies are matched to each paired galaxy in both stellar mass and redshift. In addition, we find that the sSFR enhancement is elevated in pairs with nearly equal masses and closer projected separations, in agreement with previous work based on single-fiber spectroscopy. We also find that the sSFR offsets in the outskirts of the paired galaxies are dependent on whether the galaxy is the more-massive or less-massive companion in the pair. The more-massive companion experiences zero to a positive sSFR enhancement, while the less-massive companion experiences sSFR suppression in their outskirts. Our results illustrate the complex tidal effects on star formation in closely paired galaxies.

Keywords: Galaxy interactions, Galaxy pairs, Galaxy nuclei, Star formation, Galaxy mergers
Looking for Obscured Young Star Clusters in NGC 1313. Using recently acquired Hubble Space Telescope NIR observations (J, Paβ, and H bands) of the nearby galaxy NGC 1313, we investigate the timescales required by a young star cluster to emerge from its natal cloud. We search for extincted star clusters, potentially embedded in their natal cloud as either (1) compact sources in regions with high Hα/Paβ extinctions or (2) compact H II regions that appear as point-like sources in the Paβ emission map. The NUV-optical-NIR photometry of the candidate clusters is used to derive their ages, masses, and extinctions via a least-χ2 spectral energy distribution broad- and narrowband fitting process. The 100 clusters in the final samples have masses in the range ${\mathrm{log}}_{10}(M/{M}_{\odot })=2.5\mbox{--}3.5$ and moderate extinctions, E(B - V) ≲ 1.0 mag. Focusing on the young clusters (0-6 Myr), we derive a weak correlation between extinction and age of the clusters. Almost half of the clusters have low extinctions, E(B - V) &lt; 0.25 mag, already at very young ages (≤3 Myr), suggesting that dust is quickly removed from clusters. A stronger correlation is found between the morphology of the nebular emission (compact, partial or absent, both in Hα and Paβ) and cluster age. Relative fractions of clusters associated with a specific nebular morphology are used to estimate the typical timescales for clearing the natal gas cloud, resulting in between 3 and 5 Myr, ∼1 Myr older than what was estimated from NUV-optical-based cluster studies. This difference hints at a bias for optical-only-based studies, which James Webb Space Telescope will address in the coming years.

Keywords: Compact H II region, Spiral galaxies, Young star clusters, Interstellar dust extinction, Star formation
Astrochemical Significance of the P + SO Reaction: Spectroscopic Characterization of SPO, PSO, and SOP Isomers. The doublet and quartet potential energy surfaces for the P + SO → PO + S reaction are explored using the highly accurate explicit correlation multireference configuration interaction method, and the reaction is found to be thermodynamically favorable, with an exothermicity value of 70.5 kJ mol-1. The electronic structure, spectra, and bond dissociation energies of the intermediates involved in the reaction, such as SPO, PSO, and SOP, are calculated using high-level quantum chemistry methods. An explanation of the nondetection of the diatomic SP is proposed. At pressures relevant to astrochemistry, the reaction is overwhelmingly bimolecular, with a predicted rate coefficient of 2.1 × 10-10 (T/300)-0.23 cm3 molecule-1 s-1. The results from this study are expected to aid in the spectroscopic detection of these new species in the laboratory and the interstellar medium.

Keywords: Interstellar molecules, Comets, Interstellar objects, Interstellar medium
2-aminooxazole in Astrophysical Environments: IR Spectra and Destruction Cross Sections for Energetic Processing. 2-aminooxazole (2AO), a N-heterocyclic molecule, has been proposed as an intermediate in prebiotic syntheses. It has been demonstrated that it can be synthesized from small molecules such as cyanamide and glycoaldehyde, which are present in interstellar space. The aim of this work is to provide infrared (IR) spectra, in the solid phase for conditions typical of astrophysical environments and to estimate its stability toward UV photons and cosmic rays. IR (4000-600 cm-1) absorption spectra at 20 K, 180 K, and 300 K, IR band strengths, and room-temperature UV (120-250 nm) absorption spectra are given for the first time for this species. Destruction cross sections of ≈9.5 10-18 cm2 and ≈2 10-16 cm2 were found in the irradiation at 20 K of pure 2AO and 2AO:H2O ices with UV (6.3-10.9 eV) photons or 5 keV electrons, respectively. These data were used to estimate half-life times for the molecule in different environments. It is estimated that 2AO could survive UV radiation and cosmic rays in the ice mantles of dense clouds beyond cloud collapse. In contrast, it would be very unstable on the surface of cold solar system bodies like Kuiper Belt objects, but the molecule could still survive within dust grain agglomerates or cometesimals.

Keywords: Ice destruction, Theoretical models, Spectral line identification, Laboratory astrophysics, Experimental techniques, Astrochemistry, Molecular physics, Pre-biotic astrochemistry