Sazuna/UAT_keywords huggingface dataset:
A Comparison between Nuclear Ring Star Formation in LIRGs and in Normal Galaxies with the Very Large Array. Nuclear rings are excellent laboratories for studying intense star formation. We present results from a study of nuclear star-forming rings in five nearby normal galaxies from the Star Formation in Radio Survey (SFRS) and four local LIRGs from the Great Observatories All-sky LIRG Survey at sub-kiloparsec resolutions using Very Large Array high-frequency radio continuum observations. We find that nuclear ring star formation (NRSF) contributes 49%-60% of the total star formation of the LIRGs, compared to 7%-40% for the normal galaxies. We characterize a total of 57 individual star-forming regions in these rings, and find that with measured sizes of 10-200 pc, NRSF regions in the LIRGs have star formation rate (SFR) and ΣSFR up to 1.7 M⊙ yr-1 and 402 M⊙ yr-1 kpc-2, respectively, which are about 10 times higher than in NRSF regions in the normal galaxies with similar sizes, and comparable to lensed high-z star-forming regions. At ~100-300 pc scales, we estimate low contributions (&lt;50%) of thermal free-free emission to total radio continuum emission at 33 GHz in the NRSF regions in the LIRGs, but large variations possibly exist at smaller physical scales. Finally, using archival sub-kiloparsec resolution CO (J = 1-0) data of nuclear rings in the normal galaxies and NGC 7469 (LIRG), we find a large scatter in gas depletion times at similar molecular gas surface densities, which tentatively points to a multimodal star formation relation on sub-kiloparsec scales.

Keywords: Star forming regions, Galaxy structure, Galaxy nuclei, Radio continuum emission, Luminous infrared galaxies
A Photoionization Mass Spectrometry Investigation into Complex Organic Molecules Formed in Interstellar Analog Ices of Carbon Monoxide and Water Exposed to Ionizing Radiation. The formation of complex organic molecules by energetic electrons mimicking secondary electrons generated within trajectories of galactic cosmic rays was investigated in interstellar ice analog samples of carbon monoxide and water at 5 K. Simulating the transition from cold molecular clouds to star-forming regions, newly formed products sublimed during the temperature-programmed desorption and were detected utilizing isomer-specific photoionization reflectron time-of-flight mass spectrometry. Using isotopically labeled ices, tunable photoionization, and adiabatic ionization energies to discriminate between isomers, isomers up to ${{\rm{C}}}_{2}{{\rm{H}}}_{4}{{\rm{O}}}_{2}$ and ${{\rm{C}}}_{2}{{\rm{H}}}_{6}{{\rm{O}}}_{2}$ were identified, while non-isomer-specific findings confirmed complex organics with molecular formulas up to ${{\rm{C}}}_{4}{{\rm{H}}}_{6}{{\rm{O}}}_{4}$. The results provide important constraints on reaction pathways from simple inorganic precursors to complex organic molecules that have both astrochemical and astrobiological significance.

Keywords: Interstellar molecules, Interdisciplinary astronomy, Laboratory astrophysics, Astrochemistry
Discovery of Two Infrared Objects with Strong Ice Absorption in the Akari Slitless Spectroscopic Survey of the Galactic Plane. We discover two infrared objects that show deep absorption features of H2O, CO2, and CO ices in the AKARI/Infrared Camera slitless spectroscopic survey of the Galactic plane in 2.5-13 μm. Both objects are neither located in known star-forming regions nor in known dense clouds. For one of the objects, Object 1, we successfully extract spectrum from 2.5-13 μm, which also shows several absorption features in 5-13 μm, including deep silicate absorption at 10 μm. For the other object, Object 2, only spectrum from 3.1-5 μm is reliably extracted due to the presence of nearby overlapping objects and faint nebulosity. Both objects show warm (&gt;100 K) CO gas absorption in addition to the ice absorption features, suggesting that they are embedded young stellar objects (YSOs). On the other hand, both objects have spectral energy distributions (SEDs) that peak at around 5 μm and decrease toward longer wavelengths. These characteristics of the SEDs and the presence of deep absorption features cannot easily be accounted for by standard YSO models. They may be explained as background stars behind dense clouds. We discuss possible nature of the objects and implications of the present discovery.

Keywords: Interstellar dust extinction
Thermal Emission and Radioactive Lines, but No Pulsar, in the Broadband X-Ray Spectrum of Supernova 1987A. Supernova 1987A offers a unique opportunity to study an evolving supernova in unprecedented detail over several decades. The X-ray emission is dominated by interactions between the ejecta and the circumstellar medium, primarily the equatorial ring (ER). We analyze 3.3 Ms of NuSTAR data obtained between 2012 and 2020, and two decades of XMM-Newton data. Since ~2013, the flux below 2 keV has declined, the 3-8 keV flux has increased but has started to flatten, and the emission above 10 keV has remained nearly constant. The spectra are well described by a model with three thermal shock components. Two components at 0.3 and 0.9 keV are associated with dense clumps in the ER, and a 4 keV component may be a combination of emission from diffuse gas in the ER and the surrounding low-density H II region. We disfavor models that involve nonthermal X-ray emission and place constraints on nonthermal components, but cannot firmly exclude an underlying power law. Radioactive lines show a ${}^{44}\mathrm{Ti}$ redshift of ${670}_{-380}^{+520}$ $\,\mathrm{km}\,{{\rm{s}}}^{-1}$, ${}^{44}\mathrm{Ti}$ mass of ${1.73}_{-0.29}^{+0.27}\times {10}^{-4}$ ${M}_{\odot}$, and ${}^{55}\mathrm{Fe}$ mass of $\lt 4.2\times {10}^{-4}$ ${M}_{\odot}$. The 35-65 keV luminosity limit on the compact object is $2\times {10}^{34}$ erg s-1, and $\lt 15 \% $ of the 10-20 keV flux is pulsed. Considering previous limits, we conclude that there are currently no indications of a compact object, aside from a possible hint of dust heated by a neutron star in recent ALMA images.

Keywords: Explosive nucleosynthesis, Core-collapse supernovae, Supernova remnants, Circumstellar matter, Cosmic ray sources, Shocks
Evaluating Rotation Periods of M Dwarfs across the Ages. In this work we examine M dwarf rotation rates at a range of ages to establish benchmarks for M dwarf gyrochronology. This work includes a sample of 713 spectroscopically classified M0-M8 dwarfs with new rotation rates measured from K2 light curves. We analyze data and recover rotation rates for 179 of these objects. We add these to rotation rates for members of clusters with known ages (5-700 Myr), as well as objects assumed to have field ages (≳1 Gyr). We use Gaia DR2 parallax and $(G\mbox{--}{G}_{\mathrm{RP}})$ photometry to create color-magnitude diagrams to compare objects across samples. We use color-period plots to analyze the period distributions across age, as well as incorporate Hα equivalent width and tangential velocity where possible to further comment on age dependence. We find that the age of transition from rapid to slow rotation in clusters, which we define as an elbow in the period-color plots, depends on spectral type. Later spectral types transition at older ages: M4 for Praesepe at ≈700 Myr, one of the oldest clusters for which M dwarf rotation rates have been measured. The transition from active to inactive Hα equivalent width also occurs at this elbow, as objects transition from rapid rotation to the slowly rotating sequence. Redder or smaller stars remain active at older ages. Finally, using Gaia kinematics we find evidence for rotation stalling for late Ms in the field sample, suggesting the transition happens much later for mid- to late-type M dwarfs.

Keywords: M dwarf stars, Stellar kinematics, Light curves, Stellar magnetic fields, Stellar rotation, Stellar associations
Star Formation in a Strongly Magnetized Cloud. We study star formation in the Center Ridge 1 (CR1) clump in the Vela C giant molecular cloud, selected as a high column density region that shows the lowest level of dust continuum polarization-angle dispersion, likely indicating that the magnetic field is relatively strong. We observe the source with the Atacama Large Millimeter/submillimeter Array 7 m array at 1.05 and 1.3 mm wavelengths, which enable measurements of dust temperature, core mass, and astrochemical deuteration. A relatively modest number of 11 dense cores are identified via their dust continuum emission, with masses spanning from 0.17-6.7 ${M}_{\odot}$. Overall CR1 has a relatively low compact dense gas fraction compared with other typical clouds with similar column densities, which may be a result of the strong magnetic field and/or the very early evolutionary stage of this region. The deuteration ratios, ${D}_{\mathrm{frac}}$, of the cores, measured with ${{\rm{N}}}_{2}{{\rm{H}}}^{+}$ (3-2) and ${{\rm{N}}}_{2}{{\rm{D}}}^{+}$ (3-2) lines, span from 0.011-0.85, with the latter being one of the highest values yet detected. The level of deuteration appears to decrease with evolution from prestellar to protostellar phase. A linear filament, running approximately parallel with the large scale magnetic field orientation, is seen connecting the two most massive cores, each having CO bipolar outflows aligned orthogonally to the filament. The filament contains the most deuterated core, likely to be prestellar and located midway between the protostars. The observations permit measurement of the full deuteration structure of the filament along its length, which we present. We also discuss the kinematics and dynamics of this structure, as well as of the dense core population.

Keywords: Star formation, Molecular clouds, Magnetic fields
Impact of the New Measurement of the <SUP>12</SUP>C + <SUP>12</SUP>C Fusion Cross Section on the Final Compactness of Massive Stars. We discuss how the new measurement of the 12C + 12C fusion cross section carried out with the Trojan Horse Method affects the compactness of a star, i.e., basically the binding energy of the inner mantle, at the onset of the core collapse. In particular, we find that this new cross section significantly changes the dependence of the compactness on the initial mass with respect to previous findings obtained in Chieffi &amp; Limongi by adopting the classical cross section provided by Caughlan &amp; Fowler. A non-monotonic but well-defined behavior is also confirmed in this case and no scatter of the compactness around the main trend is found. Such an occurrence could impact the possible explodability of the stars.

Keywords: Stellar physics, Stellar evolutionary models, Late stellar evolution, Stellar evolution
The First OGLE-discovered Ultracompact X-Ray Binary is an Intermediate Polar. The variable source OGLE-UCXB-01 is the first OGLE-discovered ultracompact X-ray binary (UCXB). The 12 yr long-term OGLE optical photometry of this source shows a period of $P=12.8\,\min$ and a fast period-decreasing rate $\dot{P}=-9.2\times {10}^{-11}$ s s-1. At a luminosity of ${L}_{{\rm{X}}}\approx 4\times {10}^{33}$ erg s-1, its X-ray emission is also variable and correlated with the optical variability. To determine the nature of this variable source, specifically the masses and types of its binary components, we first consider an attractive possibility that the optical variation is due to the secondary's ellipsoidal variation and a strong gravitational wave emission drives the orbital decay. However, we cannot find an allowable solution to the secondary that simultaneously satisfies the three constraints: an ultratight orbit, the bright absolute magnitude, and the large-amplitude brightness variation. Moreover, the inferred mass-transfer rate is too high. This scenario is therefore ruled out. We then find the system is fully consistent with an "intermediate polar" model, in which the optical and X-ray emission comes from a magnetized white dwarf (WD) accreting from a low-mass (≲ $0.7\,{M}_{\odot }$) main-sequence secondary. The observed period decay is the accretion-driven spin-up of the WD. The WD spin period is 12.8 minutes and the orbital period is shorter than 10 hr. The method presented here can be applied to other UCXB candidates or impostors with only time-domain data available.

Keywords: Periodic variable stars, X-ray binary stars, White dwarf stars, Stellar accretion, Magnetic variable stars
A Deeper Look at DES Dwarf Galaxy Candidates: Grus I and Indus II. We present deep g- and r-band Magellan/Megacam photometry of two dwarf galaxy candidates discovered in the Dark Energy Survey (DES), Grus I and Indus II (DES J2038-4609). For the case of Grus I, we resolved the main sequence turn-off (MSTO) and ~2 mags below it. The MSTO can be seen at g0 ~ 24 with a photometric uncertainty of 0.03 mag. We show Grus I to be consistent with an old, metal-poor (~13.3 Gyr, [Fe/H] ~ -1.9) dwarf galaxy. We derive updated distance and structural parameters for Grus I using this deep, uniform, wide-field data set. We find an azimuthally-averaged halflight radius more than two times larger (~151+21-31 pc; ~ $4\buildrel{\,\prime}\over{.} {16}_{-0.74}^{+0.54}$) and an absolute V-band magnitude ~-4.1 that is ~1 magnitude brighter than previous studies. We obtain updated distance, ellipticity, and centroid parameters that are in agreement with other studies within uncertainties. Although our photometry of Indus II is ~2-3 magnitudes deeper than the DES Y1 public release, we find no coherent stellar population at its reported location. The original detection was located in an incomplete region of sky in the DES Y2Q1 data set and was flagged due to potential blue horizontal branch member stars. The best-fit isochrone parameters are physically inconsistent with both dwarf galaxies and globular clusters. We conclude that Indus II is likely a false positive, flagged due to a chance alignment of stars along the line of sight.

Keywords: Bayesian statistics, Galaxy properties, Dwarf galaxies, Astronomy data analysis, Photometry
ALMA Observations toward the S-shaped Outflow and the Envelope around NGC 1333 IRAS 4A2. We have analyzed the ALMA archival data of the SO (JN = 65 - 54 and JN = 76 - 65), CO (J = 2 - 1), and CCH (N = 3 - 2, J = 7/2 - 5/2, F = 4 - 3) lines from the Class 0 protobinary system, NGC 1333 IRAS 4A. The images of SO (JN = 65 - 54) and CO (J = 2 - 1) successfully separate two northern outflow lobes connected to each protostar, IRAS 4A1 and IRAS 4A2. The outflow from IRAS 4A2 shows an S-shaped morphology, consisting of a flattened envelope around IRAS 4A2 with two outflow lobes connected to both edges of the envelope. The flattened envelope surrounding IRAS 4A2 has a velocity gradient opposite to that of the circumbinary envelope. The observed features are reproduced by the magnetohydrodynamic simulation of the collapsing core whose magnetic field direction is misaligned with the rotational axis. Our simulation shows that the intensity of the outflow lobes is enhanced on one side, resulting in the formation of S-shaped morphology. The S-shaped outflow can also be explained by the precessing outflow launched from an unresolved binary with a separation larger than 12 au (0"04). Additionally, we discovered a previously unknown extremely high-velocity component at ~45-90 km s-1 near IRAS 4A2 with CO. CCH (JN,F = 7/23,4 - 5/22,3) emission shows two pairs of blobs attached to the bottom of a shell-like feature, and the morphology is significantly different from that of the SO and CO lines. Toward IRAS 4A2, the S-shaped outflow shown in SO is overlapped with the edges of CCH shells, while CCH shells have velocity gradients opposite to those of the flattened structure around IRAS 4A2.

Keywords: Young stellar objects, Stellar winds, Star formation, Protostars, Magnetohydrodynamical simulations
Classification of Filament Formation Mechanisms in Magnetized Molecular Clouds. Recent observations of molecular clouds show that dense filaments are the sites of present-day star formation. Thus, it is necessary to understand the filament formation process because these filaments provide the initial condition for star formation. Theoretical research suggests that shock waves in molecular clouds trigger filament formation. Since several different mechanisms have been proposed for filament formation, the formation mechanism of the observed star-forming filaments requires clarification. In the present study, we perform a series of isothermal magnetohydrodynamics simulations of filament formation. We focus on the influences of shock velocity and turbulence on the formation mechanism and identified three different mechanisms for the filament formation. The results indicate that when the shock is fast, at shock velocity vsh ≃ 7 km s-1, the gas flows driven by the curved shock wave create filaments irrespective of the presence of turbulence and self-gravity. However, at a slow shock velocity vsh ≃ 2.5 km s-1, the compressive flow component involved in the initial turbulence induces filament formation. When both the shock velocities and turbulence are low, the self-gravity in the shock-compressed sheet becomes important for filament formation. Moreover, we analyzed the line-mass distribution of the filaments and showed that strong shock waves can naturally create high-line-mass filaments such as those observed in the massive star-forming regions in a short time. We conclude that the dominant filament formation mode changes with the velocity of the shock wave triggering the filament formation.

Keywords: Magnetohydrodynamics, Star formation, Interstellar clouds
Near-Sun Switchback Boundaries: Dissipation with Solar Distance. The most surprising result from the first solar encounters by the Parker Solar Probe (PSP) is the large amount of brief magnetic field reversals often referred to as switchbacks. Switchbacks have previously been observed further downstream in the solar wind by spacecraft such as Helios 2 at 62 Rs from the Sun. However, these observations lack a distinct proton temperature increase detected inside switchbacks by PSP, implying that they are evolving over time to eventually reach a pressure balance at the switchback boundaries. We look at the evolution of switchback boundaries as a function of radial distance from the Sun, from closest approach at 35.7 Rs during PSP's first two encounters to beyond 80 Rs. Using magnetic field and proton data from PSP's FIELDS and SWEAP instruments, we perform a day-by-day superposed epoch analysis of the 25 switchbacks with the sharpest step-like boundaries. During both encounters we found the proton temperature spikes to gradually decline before vanishing completely around 55 Rs. Magnetic reversals and velocity spikes also steadily drop in magnitude, but eventually flatten out instead of disappearing. Most interestingly, proton temperature change ΔTp across switchback boundaries is found to reach 2 × 105 in magnitude below 40 Rs during PSP's outbound trajectory, but is an order of magnitude less on the inbound trajectory, suggesting a possible common change in switchback characteristics near closest approach during both encounters.

Keywords: The Sun, Solar wind, Solar physics
Molecular Dynamics Approach for Predicting Release Temperatures of Noble Gases in Presolar Nanodiamonds. Presolar meteoritic nanodiamond grains carry an array of isotopically distinct noble gas components and provide information on the history of nucleosynthesis, galactic mixing, and the formation of the solar system. In this paper, we develop a molecular dynamics approach to predict the thermal release pattern of implanted noble gases (He and Xe) in nanodiamonds. We provide atomistic details of the unimodal temperature release distribution for He and a bimodal behavior for Xe. Intriguingly, our model shows that the thermal release process of noble gases is highly sensitive to the impact and annealing parameters, as well as the position of the implanted ion in the crystal lattice and morphology of the nanograin. In addition, the model elegantly explains the unimodal and bimodal patterns of noble gas release via the interstitial and substitutional types of defects formed. In summary, our simulations confirm that low-energy ion implantation is a viable way to incorporate noble gases into nanodiamonds, and we provide an explanation of the experimentally observed peculiarities of gas release.

Keywords: Meteorites, N-body simulations
Feeding the Accretion Disk from the Dusty Torus in a Reddened Quasar. We present here a detailed analysis of an unusual absorption line system in the quasar SDSS J122826.79+100532.2. The absorption lines in the system have a common redshifted velocity structure starting from v ~ 0 and extending to ~1000 km s-1, and are clearly detected in the hydrogen Balmer series up to Hι, in the metastable neutral helium triplet, and in optical lines of excited states of single ionized iron. We estimated that the absorber has a density nH ≈ 108.4 cm-3 and an ionization parameter U ≈ 10-1.2, thereupon we located it at rabs ≈ 1.5 pc from the central supermassive black hole. The inferred distance is remarkably similar to the evaporation radius for dust grains revap ≈ 1 pc in the quasar. Thus the absorber may be a probe of an inflow starting from the dusty torus and feeding the accretion disk. Both the featureless continuum and the broad emission lines are heavily reddened with E(B - V) ≈ 0.66, in contrast to the narrow emission lines whose reddening is negligible. The dusty medium could be located in between the broad and narrow emission line regions, and possibly be associated with a "cold" narrow absorption line system detected in Ca II and Na I doublets nearly unshifted from the quasar systemic velocity. SDSS J122826.79+100532.2 might represent such a rare case that both the inflow and the torus could be tracked by absorption lines.

Keywords: Quasar absorption line spectroscopy, Quasars
Characterizing Solar Surface Convection Using Doppler Measurements. The Helioseismic Magnetic Imager on board the Solar Dynamics Observatory records line-of-sight Dopplergram images of convective flows on the surface. These images are used to obtain the multiscale convective spectrum. We design a pipeline to process the raw images to remove large-scale features like differential rotation, meridional circulation, limb shift, and imaging artifacts. The Hierarchical Equal Area Pixelization scheme is used to perform spherical harmonic transforms on the cleaned image. Because we only have access to line-of-sight velocities on half the solar surface, we define a "mixing matrix" to relate the observed and true spectra. This enables the inference of poloidal and toroidal flow spectra in a single step through the inversion of the mixing matrix. Performing inversions on a number of flow profiles, we find that the poloidal flow recovery is most reliable among all the components. We also find that the poloidal spectrum is in qualitative agreement with inferences from Local Correlation Tracking of granules. The fraction of power in vertical motions increases as a function of wavenumber and is at the 8% level for ℓ = 1500. In contrast to seismic results and LCT, the flows show nearly no temporal-frequency dependence. Poloidal flow power peaks in the range of ℓ - ∣m∣ ≈ 150-250, which may potentially hint at a latitudinal preference for convective flows.

Keywords: Supergranulation, Solar photosphere