Sazuna/UAT_keywords huggingface dataset:
The ALMA Spectroscopic Survey in the HUDF: A Search for [C II] Emitters at 6 ≤ z ≤ 8. The Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Band 6 scan (212-272 GHz) covers potential [C II] emission in galaxies at 6 ≤ z ≤ 8 throughout a 2.9 arcmin2 area. By selecting on known Lyα emitters (LAEs) and photometric dropout galaxies in the field, we perform targeted searches down to a 5σ [C II] luminosity depth L[C II] ∼ 2.0 × 108 L☉, corresponding roughly to star formation rates (SFRs) of 10-20 M☉ yr-1 when applying a locally calibrated conversion for star-forming galaxies, yielding zero detections. While the majority of galaxies in this sample are characterized by lower SFRs, the resulting upper limits on [C II] luminosity in these sources are consistent with the current literature sample of targeted ALMA observations of z = 6-7 LAEs and Lyman-break galaxies (LBGs), as well as the locally calibrated relations between L[C II] and SFR—with the exception of a single [C II]-deficient, UV-luminous LBG. We also perform a blind search for [C II]-bright galaxies that may have been missed by optical selections, resulting in an upper limit on the cumulative number density of [C II] sources with L[C II] &gt; 2.0 × 108 L☉ (5σ) to be less than 1.8 × 10-4 Mpc-3 (90% confidence level). At this luminosity depth and volume coverage, we present an observed evolution of the [C II] luminosity function from z = 6-8 to z ∼ 0 by comparing the ASPECS measurement to literature results at lower redshift.

Keywords: High-redshift galaxies, Interstellar medium
Simultaneous Deep Measurements of CO Isotopologues and Dust Emission in Giant Molecular Clouds in the Andromeda Galaxy. We present simultaneous measurements of emission from dust continuum at 230 GHz and the J = 2-1 12CO, 13CO, and C18O isotopologues at ∼15 pc resolution from individual giant molecular clouds (GMCs) in the Andromeda galaxy (M31). These observations were obtained in an ongoing survey of this galaxy being conducted with the Submillimeter Array. Initial results describing the continuum and 12CO emission have been published earlier. Here, we primarily analyze the observations of 13CO and C18O emission and compare them to the measurements of dust continuum and 12CO emission. We also report additional dust continuum and CO measurements from newly added GMCs to the M31 sample. We detect spatially resolved 13CO emission with high signal-to-noise ratios in 31 objects. We find the extent of the 13CO emission to be nearly comparable to that of 12CO, typically covering 75% of the area of the 12CO emission. We derive 13CO and C18O abundances of 2.9 × 10-6 and 4.4 × 10-7 relative to H2, respectively, by comparison with hydrogen column densities of the same regions derived from the dust continuum observations assuming a Milky Way gas-to-dust ratio. We find the isotopic abundance ratio [13CO]/[C18O] = 6.7 ± 2.9 to be consistent with the Milky Way value (8.1). Finally, we derive the mass-to-light conversion factors for all three CO species to be α12 = 8.7 ± 3.9, α13 = 48.9 ± 20.4, and ${\alpha }_{18}={345}_{-31}^{+25}$ M⊙ (K km s-1 pc2)-1 for the J = 2-1 transitions of 12CO, 13CO, and C18O, respectively.

Keywords: Giant molecular clouds, Dust continuum emission, Andromeda Galaxy, CO line emission
Thermodynamical Description of Hot, Rapidly Rotating Neutron Stars, Protoneutron Stars, and Neutron Star Merger Remnants. The prediction of the equation of state of hot, dense nuclear matter is one of the most complicated and interesting problems in nuclear astrophysics. At the same time, knowledge of it is the basic ingredient for some of the most interesting studies. In the present work, we concentrate our study on the construction of the equation of state of hot, dense nuclear matter, related mainly to the interior of the neutron star. We employ a theoretical nuclear model, which includes momentum-dependent interaction among the nucleons, along with state-of-the-art microscopic calculations. Thermal effects are introduced in a self-consistent way, and a set of isothermal and isentropic equations of state are predicted. The predicted equations of state are used in order to acquire and extend the knowledge of the thermal effect on both nonrotating and rapidly rotating with the Kepler frequency neutron stars. The simultaneous study of thermal and rotation effects provides useful information on some of the most important quantities, including the mass (gravitational and baryon) and radius, the Kepler frequency and Kerr parameter, the moment of inertia, etc. These quantities are directly related to studies of protoneutron stars and mainly the hot and rapidly rotating remnant of a binary neutron star merger. Data from the late observations of binary neutron star mergers and the present study may offer useful tools for investigation and help in providing possible constraints on the equation of state of nuclear matter.

Keywords: Neutron stars, Relativistic binary stars, Nuclear astrophysics, Nuclear physics
The Twins Embedding of Type Ia Supernovae. I. The Diversity of Spectra at Maximum Light. We study the spectral diversity of Type Ia supernovae (SNe Ia) at maximum light using high signal-to-noise spectrophotometry of 173 SNe Ia from the Nearby Supernova Factory. We decompose the diversity of these spectra into different extrinsic and intrinsic components, and we construct a nonlinear parameterization of the intrinsic diversity of SNe Ia that preserves pairings of "twin" SNe Ia. We call this parameterization the "Twins Embedding." Our methodology naturally handles highly nonlinear variability in spectra, such as changes in the photosphere expansion velocity, and uses the full spectrum rather than being limited to specific spectral line strengths, ratios, or velocities. We find that the time evolution of SNe Ia near maximum light is remarkably similar, with 84.6% of the variance in common to all SNe Ia. After correcting for brightness and color, the intrinsic variability of SNe Ia is mostly restricted to specific spectral lines, and we find intrinsic dispersions as low as ∼0.02 mag between 6600 and 7200 Å. With a nonlinear three-dimensional model plus one dimension for color, we can explain 89.2% of the intrinsic diversity in our sample of SNe Ia, which includes several different kinds of "peculiar" SNe Ia. A linear model requires seven dimensions to explain a comparable fraction of the intrinsic diversity. We show how a wide range of previously established indicators of diversity in SNe Ia can be recovered from the Twins Embedding. In a companion article, we discuss how these results can be applied to the standardization of SNe Ia for cosmology.

Keywords: Standard candles, Observational cosmology, Type Ia supernovae
The Twins Embedding of Type Ia Supernovae. II. Improving Cosmological Distance Estimates. We show how spectra of Type Ia supernovae (SNe Ia) at maximum light can be used to improve cosmological distance estimates. In a companion article, we used manifold learning to build a three-dimensional parameterization of the intrinsic diversity of SNe Ia at maximum light that we call the "Twins Embedding." In this article, we discuss how the Twins Embedding can be used to improve the standardization of SNe Ia. With a single spectrophotometrically calibrated spectrum near maximum light, we can standardize our sample of SNe Ia with an rms of 0.101 ± 0.007 mag, which corresponds to 0.084 ± 0.009 mag if peculiar velocity contributions are removed and to 0.073 ± 0.008 mag if a larger reference sample were obtained. Our techniques can standardize the full range of SNe Ia, including those typically labeled as peculiar and often rejected from other analyses. We find that traditional light-curve width + color standardization such as SALT2 is not sufficient. The Twins Embedding identifies a subset of SNe Ia, including, but not limited to, 91T-like SNe Ia whose SALT2 distance estimates are biased by 0.229 ± 0.045 mag. Standardization using the Twins Embedding also significantly decreases host-galaxy correlations. We recover a host mass step of 0.040 ± 0.020 mag compared to 0.092 ± 0.026 mag for SALT2 standardization on the same sample of SNe Ia. These biases in traditional standardization methods could significantly impact future cosmology analyses if not properly taken into account.

Keywords: Standard candles, Observational cosmology, Type Ia supernovae
COLDz: Deep 34 GHz Continuum Observations and Free-Free Emission in High-redshift Star-forming Galaxies. The high-frequency radio sky has historically remained largely unexplored due to the typical faintness of sources in this regime, and the modest survey speed compared to observations at lower frequencies. However, high-frequency radio surveys offer an invaluable tracer of high-redshift star formation, as they directly target the faint radio free-free emission. We present deep continuum observations at 34 GHz in the COSMOS and GOODS-North fields from the Karl G. Jansky Very Large Array (VLA), as part of the COLDz survey. The deep COSMOS mosaic spans $\sim 10\,{\mathrm{arcmin}}^{2}$ down to σ = 1.3 μJy beam-1, while the wider GOODS-N observations cover $\sim 50\,{\mathrm{arcmin}}^{2}$ to σ = 5.3 μJy beam-1. We detect a total of 18 galaxies at 34 GHz, of which nine show radio emission consistent with being powered by star formation; although for two sources, this is likely due to thermal emission from dust. Utilizing deep ancillary radio data at 1.4, 3, 5, and 10 GHz, we decompose the spectra of the remaining seven star-forming galaxies into their synchrotron and thermal free-free components, and find typical thermal fractions and synchrotron spectral indices comparable to those observed in local star-forming galaxies. We further determine free-free star formation rates (SFRs), and show that these are in agreement with SFRs from spectral energy distribution-fitting and the far-infrared/radio correlation. Our observations place strong constraints on the high-frequency radio emission in typical galaxies at high redshift, and provide some of the first insights into what is set to become a key area of study with future radio facilities, such as the Square Kilometer Array Phase 1 and next-generation VLA.

Keywords: Radio continuum emission, Galaxy formation, High-redshift galaxies, Galaxy evolution
Chemical Analysis of Two Extremely Metal-poor Stars HE 2148-2039 and HE 2155-2043. We present elemental abundance results for HE 2148-2039 and HE 2155-2043 based on a detailed high-resolution spectroscopic analysis. The high-resolution Subaru/High Dispersion Spectrograph (HDS) spectra used for our analysis have a resolution of R ∼ 60,000. Although limited information based on photometry and low-resolution spectroscopy is available, we present for the first time an abundance analysis based on high-resolution spectra for both objects. Our analysis shows that the two objects are extremely metal-poor with [Fe/H] &lt; -3. Among the neutron-capture elements, abundances of only Sr and Ba could be determined in our program stars. For both the objects [Ba/Fe] is found to be &lt;0. While strontium is underabundant in HE 2148-2039 with [Sr/Fe] ∼ -2.02, Sr is near solar in HE 2155-2043. The locations of the program stars in the absolute carbon abundance, A(C) versus [Fe/H] diagram, show that HE 2148-2039 is a carbon-enhanced metal-poor (CEMP)-no Group II object and HE 2155-2043 is a CEMP-no Group III object. Observed [Sr/Ba] ratios are characteristics of a fast rotating massive star progenitor for HE 2155-2043 and a metal-poor asymptotic giant branch (AGB) star for HE 2148-2039. The estimated [Sc/Mn] as well as [C/Cr] ratios in HE 2155-2043 show that the surface chemical composition of this object is mono-enriched. The surface chemical composition of HE 2148-2039 is also found to be mono-enriched based on the [Mg/C] ratio. With respect to their locations in the [C/N] versus Teff diagram, HE 2148-2039 shows signatures of mixing, and HE 2155-2043 falls in the unmixed region of the [C/N] versus Teff plot. Kinematic analysis shows that both objects belong to the Galactic halo population. * Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. The data are retrieved from the JVO portal (http://jvo.nao.ac.jp/portal/v2/) operated by the NAOJ.

Keywords: Population II stars
Large-amplitude Prominence Oscillations following Impact by a Coronal Jet. Observational evidence shows that coronal jets can hit prominences and set them in motion. The impact leads to large-amplitude oscillations (LAOs) in the prominence. In this paper, we attempt to understand this process via 2.5D MHD numerical experiments. In our model, the jets are generated in a sheared magnetic arcade above a parasitic bipolar region located in one of the footpoints of the filament channel (FC) supporting the prominence. The shear is imposed at velocities not far above the observed photospheric values; this leads to a multiple reconnection process, as obtained in previous jet models. Both a fast Alfvénic perturbation and a slower supersonic front preceding a plasma jet are issued from the reconnection site; in the later phase, a more violent (eruptive) jet is produced. The perturbation and jets run along the FC; they are partially reflected at the prominence, and partially transmitted through it. This results in a pattern of counter-streaming flows along the FC, and oscillations in the prominence. The oscillations are LAOs (i.e., with amplitudes above 10 km s-1) in some areas of the prominence, both in the longitudinal and transverse directions. In some field lines, the impact is so strong that the prominence mass is brought out of the dip and down to the chromosphere along the FC. Two cases are studied, with respect to arcades at different heights above the parasitic bipolar region, leading to different heights for the region of the prominence perturbed by the jets. The obtained oscillation amplitudes and periods are in general agreement with the observations.

Keywords: Jets, Solar prominences, Plasma jets, Solar filaments, Solar corona, Solar coronal waves
The Be Star 66 Ophiuchi: 60 Years of Disk Evolution. We use a time-dependent hydrodynamic code and a non-LTE Monte Carlo code to model disk dissipation for the Be star 66 Ophiuchi. We compiled 63 years of observations from 1957 to 2020 to encompass the complete history of the growth and subsequent dissipation of the star's disk. Our models are constrained by new and archival photometry, spectroscopy, and polarization observations, allowing us to model the disk dissipation event. Using Markov Chain Monte Carlo methods, we find that the properties of 66 Oph are consistent with those of a standard B2Ve star. We computed a grid of 61,568 Be star disk models to constrain the density profile of the disk before dissipation using observations of the Hα line profile and spectral energy distribution. We find at the onset of dissipation the disk has a base density of 2.5 × 10-11 g cm-3 with a radial power-law index of n = 2.6. Our models indicate that after 21 yr of disk dissipation 66 Oph's outer disk remained present and bright in the radio. We find an isothermal disk with constant viscosity with an α = 0.4 and an outer disk radius of ∼115 stellar radii best reproduces the rate of 66 Oph's disk dissipation. We determined the interstellar polarization in the direction of the star in the V band is p = 0.63 ± 0.02% with a polarization position angle of θIS ≈ 85°7 ± 0°7. Using the Stokes QU diagram, we find the intrinsic polarization position angle of 66 Oph's disk is θint ≈ 98° ± 3°.

Keywords: Early-type stars, Emission line stars, Starlight polarization, Circumstellar disks, Be stars, Circumstellar gas
Solar Cycle, Seasonal, and Dust-storm-driven Variations of the Mars Upper Atmospheric State and H Escape Rate Derived from the Lyα Emission Observed by NASA's MAVEN Mission. An accurate and systematic quantification of the state variables in the Mars upper atmosphere is important for the study of Mars volatile evolution. In this study, we perform a comprehensive analysis of the Lyα limb scans observed by MAVEN during Martian years 32-35 to quantify the Mars upper atmospheric temperature, the CO2 density, the H density, and the H thermal escape rate. A previously uncharacterized feature of the proton aurora at Mars is reported, which affects the overall shape of the limb scans without introducing peak intensity structures. Our inversion results excluding such scans demonstrate an unambiguous and systematic consistency of the Mars exobase temperature (∼150-280 K) derived from the dayside Lyα emission with those derived from the CO2+ airglow emission and those from atmospheric drag measurements, resolving a long-standing discrepancy between those different estimates. The temperature is shown to be highly predictable over different solar cycles and seasons. However, the H density and escape rate can be episodically enhanced by a factor of ∼2-3, likely driven by dust storms that coincided with the enhancements. During the three Martian years, the averaged thermal escape rates between Mars solar longitude 0°-180° and 210°-330° are 0.6 × 107 cm-2 s-1 and 9.0 × 107 cm-2 s-1, respectively, a factor of 15 seasonal difference, with a factor of ∼7.5 and ∼2 due to temperature and H density variations, respectively. These temperatures and thermal escape rates derived from the thermospheric Lyα emission are generally lower than those derived from the exospheric Lyα emission in the literature, indicating the presence of a hot H population in the Mars exosphere.

Keywords: Atmospheric composition, Mars, Aeronomy
TESS Observations of TX Col: Rapidly Varying Accretion Flow. Using the first long-term photometry from the Transiting Exoplanet Survey Satellite, we have carried out a detailed time-resolved timing analysis of an intermediate polar TX Col. The power spectra of almost 52 days of continuous time-series data reveal the orbital period of 5.691 ± 0.006 hr, spin period of 1909.5 ± 0.2 s, and beat period of 2105.76 ± 0.25 s, which is consistent with the earlier results. We have also found the presence of quasi-periodic oscillations (QPOs) for a few days with a period of 5850-5950 s, which appears to be due to the beating of the Keplerian period with the spin period of the white dwarf. The continuous data allowed us to look thoroughly at the day-wise evolution of the system's accretion geometry. We report here that the TX Col changes its accretion mechanism even on a timescale of one day, confirming its variable disk-overflow accretion nature. For the majority of the time, it was found to be disk-overflow system with stream-fed dominance; however, pure disk-fed and pure stream-fed accretions cannot be ruled out during the observations.

Keywords: DQ Herculis stars, Cataclysmic variable stars, Semi-detached binary stars
Dynamical and Thermal Manifestations of the Region above the Top of the Post-flare Loops: MHD Simulations. Observations proved that a distributed structure named a supra-arcade fan (SAF) exists above post-flare loops in solar eruptions. The locations of the SAF are spatially consistent with various emission sources. Termination shocks (TSs) that are often regarded as an efficient driver for particle acceleration possibly exist in the SAF. We performed the numerical simulations of solar flares based on the standard flare model to study the dynamical and thermal manifestations of the SAF, as well as the possibility of detecting TSs in extreme-ultraviolet (EUV) images. In the simulations, the SAF and TSs can be clearly identified. The motion history and temperature evolution of plasmas inside the SAF indicate that the mass of the SAF comes from the corona and the plasmas are heated in the current sheet. The height of the SAF decreases with the speed of about 64.6 km s-1 when the rate of magnetic reconnection quickly increases, and then increases with a slightly lower velocity of about 50.5 km s-1 after the peak of the rate of magnetic reconnection. The descent-ascent path of the SAF is due to the unbalance of the Lorentz force and the pressure force inside the magnetic loops. In synthetic EUV images, emission intensity variations in the area surrounding TSs are significant, indicating that, depending on the viewing angle, TSs could be identifiable in EUV observations. The results of numerical simulations are generally consistent with observations, helping us to better understand the characteristics of the SAF and the physical natures behind it.

Keywords: Termination shock, Solar flares, Solar magnetic reconnection, Magnetohydrodynamical simulations
Fast Ejecta as a Potential Way to Distinguish Black Holes from Neutron Stars in High-mass Gravitational-wave Events. High-mass gravitational-wave events in the neutron-star mass range, such as GW190425, have recently started to be detected by the LIGO/Virgo detectors. If the masses of the two binary components fall in the neutron-star mass range, such a system is typically classified as a binary neutron-star system, although the detected gravitational-wave signal may be too noisy to clearly establish a neutron-star nature of the high-mass component in the binary and rule out a black hole-neutron star system for such an event. We show that high-mass binary neutron-star mergers with a very massive neutron-star primary close to the maximum-mass limit, m1 ≳ 2.2 M⊙, produce fast dynamical mass ejecta from the spin-up of the primary star at merger. By simulating the merger of black hole-neutron star systems of exactly the same masses and spins, we show that these fast ejecta are entirely absent if the primary is instead a black hole. In addition, we find that both systems leave almost identical amounts of baryon mass behind, which is not immediately accreted by the black hole. This implies that both systems will likely have comparable electromagnetic afterglow emission stemming from the remnant disk. Hence, fast ejecta at merger have the potential to distinguish neutron stars from black holes in high-mass mergers, although these ejecta may be challenging to detect observationally.

Keywords: Neutron stars, General relativity, Gravitational waves
Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton. Solar and stellar flares are powerful events that produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal processes in stellar flares, we have searched the databases of Kepler (optical observations) and XMM-Newton (soft X-rays) for the flares observed simultaneously with both instruments; nine distinctive flares (with energies exceeding 1033 erg) on three stars (of K-M spectral classes) have been found. We have analyzed and compared the flare parameters in the optical and X-ray spectral ranges; we have also compared the obtained results with similar observations of solar flares. Most of the studied stellar flares released more energy in the optical range than in X-rays. In one flare, X-ray emission strongly dominated, which could be caused either by a soft spectrum of energetic electrons or by a near-limb position of this flare. The X-ray flares were typically delayed with respect to and shorter than their optical counterparts, which is partially consistent with the Neupert effect. Using the scaling laws based on the magnetic reconnection theory, we have estimated the characteristic magnetic field strengths in the stellar active regions and the sizes of these active regions as about 25-70 G and 250,000-500,000 km, respectively. The observed stellar superflares appear to be scaled-up versions of solar flares, with a similar underlying mechanism and nearly the same characteristic magnetic field values, but with much larger active region sizes.

Keywords: Markov chain Monte Carlo, Optical flares, Stellar x-ray flares