Sazuna/UAT_keywords huggingface dataset:
Polycyclic Aromatic Hydrocarbons, Anomalous Microwave Emission, and their Connection to the Cold Neutral Medium. Using new large-area maps of the cold neutral medium (CNM) fraction, f CNM, we investigate the relationship between the CNM, the abundance of polycyclic aromatic hydrocarbons (PAHs), and the anomalous microwave emission (AME). We first present our f CNM map based on full-sky HI4PI data, using a convolutional neural network to convert the spectroscopic H I data to f CNM. We demonstrate that f CNM is strongly correlated with the fraction of dust in PAHs as estimated from mid- and far-infrared dust emission. In contrast, we find no correlation between f CNM and the amount of AME per dust emission and no to weakly negative correlation between f CNM and the AME peak frequency. These results suggest PAHs preferentially reside in cold, relatively dense gas, perhaps owing to enhanced destruction in more diffuse media. The lack of positive correlation between f CNM and AME peak frequency is in tension with expectations from theoretical models positing different spectral energy distributions of AME in the cold versus warm neutral medium. We suggest that different PAH abundances and emission physics in different interstellar environments may explain the weaker-than-expected correlation between 12 μm PAH emission and AME even if PAHs are the AME carriers.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, H I line emission, Cold neutral medium, Dust continuum emission, Interstellar medium, Warm neutral medium
Fluorine Abundances in the Galactic Nuclear Star Cluster. Abundances of fluorine (19F), as well as isotopic ratios of 16O/17O, are derived in a sample of luminous young (~107-108 yr) red giants in the Galactic center (with galactocentric distances ranging from 0.6-30 pc), using high-resolution infrared spectra and vibration-rotation lines of H19F near λ2.3 μm. Five of the six red giants are members of the Nuclear star cluster that orbits the central supermassive black hole. Previous investigations of the chemical evolution of 19F in Galactic thin and thick-disk stars have revealed that the nucleosynthetic origins of 19F may be rather complex, resulting from two, or more, astrophysical sites; fluorine abundances behave as a primary element with respect to Fe abundances for thick-disk stars and as a secondary element in thin-disk stars. The Galactic center red giants analyzed fall within the thin-disk relation of F with Fe, having near-solar, to slightly larger, abundances of Fe (&lt;[Fe/H]&gt; = +0.08 ± 0.04), with a slight enhancement of the F/Fe abundance ratio (&lt;[F/Fe]&gt; = +0.28 ± 0.17). In terms of their F and Fe abundances, the Galactic center stars follow the thin-disk population, which requires an efficient source of 19F that could be the winds from core-He burning Wolf-Rayet stars, or thermally pulsing AGB stars, or a combination of both. The observed increase of [F/Fe] with increasing [Fe/H] found in thin-disk and Galactic center stars is not predicted by any published chemical evolution models that are discussed, thus a quantitative understanding of yields from the various possible sources of 19F remains unknown.

Keywords: Galactic center, Stellar abundances, Chemical abundances, Infrared telescopes, Spectroscopy, Giant stars
The Primary Proton Spectrum of the Hadronic PeVatron Candidate HAWC J1825-134. The γ-ray spectrum of the source HAWC J1825-134 measured with the High Altitude Water Cherenkov (HAWC) observatory extends beyond 200 TeV without any evidence for a steepening or cutoff. There are some indications that the γ-rays detected with HAWC were produced by cosmic-ray protons or nuclei colliding with the ambient gas. Assuming primary protons, we inquire which shape of the primary proton spectrum is compatible with the HAWC measurements. We find that the primary proton spectrum with the power-law shape of γ  p  = 2.2 and the cutoff energy E  c-p  &gt; 500 TeV describes the data well. However, much harder spectra with γ  p  down to 1.3 and E  c-p  as low as 200 TeV also do not contradict the HAWC measurements. The former option might be realized if the accelerator is inside or very near to the γ-ray production zone. The latter option is viable for the case of a cosmic-ray source that effectively confines low-energy (E  p  &lt; 10 TeV) accelerated protons. Using publicly available data of the Fermi-LAT space γ-ray telescope, we derive upper limits on the intensity of the HAWC J1825-134 source in the 1 GeV-1 TeV energy range. We show that the account of these upper limits drastically changes the interpretation: only hard (γ  p  &lt; 1.7) spectra describe the combined HAWC and Fermi-LAT data sets well.

Keywords: Gamma-ray observatories, High energy astrophysics, Gamma-ray sources, Galactic cosmic rays, Gamma-ray astronomy, Gamma-rays
Improving White Dwarfs as Chronometers with Gaia Parallaxes and Spectroscopic Metallicities. White dwarfs (WDs) offer unrealized potential in solving two problems in astrophysics: stellar age accuracy and precision. WD cooling ages can be inferred from surface temperatures and radii, which can be constrained with precision by high-quality photometry and parallaxes. Accurate and precise Gaia parallaxes along with photometric surveys provide information to derive cooling and total ages for vast numbers of WDs. Here we analyze 1372 WDs found in wide binaries with main-sequence (MS) companions and report on the cooling and total age precision attainable in these WD+MS systems. The total age of a WD can be further constrained if its original metallicity is known because the MS lifetime depends on metallicity at fixed mass, yet metallicity is unavailable via spectroscopy of the WD. We show that incorporating spectroscopic metallicity constraints from 38 wide binary MS companions substantially decreases internal uncertainties in WD total ages compared to a uniform constraint. Averaged over the 38 stars in our sample, the total (internal) age uncertainty improves from 21.04% to 16.77% when incorporating the spectroscopic constraint. Higher mass WDs yield better total age precision; for eight WDs with zero-age MS masses ≥2.0 M ⊙, the mean uncertainty in total ages improves from 8.61% to 4.54% when incorporating spectroscopic metallicities. We find that it is often possible to achieve 5% total age precision for WDs with progenitor masses above 2.0 M ⊙ if parallaxes with ≤1% precision and Pan-STARRS g, r, and i photometry with ≤0.01 mag precision are available.

Keywords: White dwarf stars, Stellar evolution
Studying Magnetic Fields and Dust in M17 Using Polarized Thermal Dust Emission Observed by SOFIA/HAWC+. We report on the highest spatial resolution measurement to date of magnetic fields (B-fields) in M17 using thermal dust polarization measurements taken by SOFIA/HAWC+ centered at a wavelength of 154 μm. Using the Davis-Chandrasekhar-Fermi method, in which the polarization angle dispersion calculated using the structure function technique is the quantity directly observed by SOFIA/HAWC+, we found the presence of strong B-fields of 980 ± 230 and 1665 ± 885 μG in the lower-density M17-N and higher-density M17-S regions, respectively. The B-field morphology in M17-N possibly mimics the fields in gravitationally collapsing molecular cores, while in M17-S the fields run perpendicular to the density structure. M17-S also displays a pillar feature and an asymmetric large-scale hourglass-shaped field. We use the mean B-field strengths to determine Alfvénic Mach numbers for both regions, finding that B-fields dominate over turbulence. We calculate the mass-to-flux ratio, λ, finding λ = 0.07 for M17-N and 0.28 for M17-S. These subcritical λ values are consistent with the lack of massive stars formed in M17. To study dust physics, we analyze the relationship between dust polarization fraction, p, emission intensity, I, gas column density, N(H2), polarization angle dispersion function, S, and dust temperature, T d. p decreases with intensity as I -α  with α = 0.51. p tends to first increase with T d, but then decreases at higher T d. The latter feature, seen in M17-N at high T d when N(H2) and S decrease, is evidence of the radiative torque disruption effect.

Keywords: Interstellar dust, Astrophysical magnetism, Star forming regions, Interstellar magnetic fields, Stellar winds, Star formation, Interstellar dust processes, Magnetic fields
Simple Analytic Formula Relating the Mass and Spin of Accreting Compact Objects to Their Rapid X-Ray Variability. Following the previous research on epicyclic oscillations of accretion disks around black holes (BHs) and neutron stars (NSs), a new model of high-frequency quasiperiodic oscillations (QPOs) has been proposed, so-called cusp torus (CT) model, which deals with oscillations of fluid in marginally overflowing accretion tori (i.e., tori terminated by cusps). According to preliminary investigations, the model provides better fits of the NS QPO data compared to the relativistic precession (RP) model. It also implies a significantly higher upper limit on the Galactic microquasar BH spins. A short analytic formula has been noticed to well reproduce the model's predictions on the QPO frequencies in Schwarzschild spacetimes. Here we derive an extended version of this formula that applies to rotating compact objects. We start with the consideration of Kerr spacetimes and derive a formula that is not restricted to a particular specific angular momentum distribution of the inner accretion flow, such as a Keplerian or constant one. Finally, we consider Hartle-Thorne spacetimes and include corrections implied by the NS oblateness. For a particular choice of a single parameter, our relation provides frequencies predicted by the CT model. For another value, it provides frequencies predicted by the RP model. We conclude that the formula is well applicable to rotating oblate NSs and both models. We briefly illustrate the application of our simple formula on several NS sources and confirm the expectation that the CT model is compatible with realistic values of the NS mass and provides better fits of data than the RP model.

Keywords: Accretion, Black hole physics, X-ray binary stars
Detection of Gravitational Redshift in Open Cluster Nondegenerate Stars. A key observational prediction of Einstein's Equivalence Principle is that light undergoes redshift when it escapes from a gravitational field. Although astrophysics provides a wide variety of physical conditions in which this redshift should be significant, until very recently the observational evidence for this gravitational effect was limited to the light emitted by the Sun and white dwarfs. Gaia-DR2 astrometric and kinematic data, in combination with other spectroscopic observations, provides a test bench to validate such predictions in statistical terms. The aim of this paper is to analyze several thousand main-sequence and giant stars in open clusters (OCs) in order to measure the gravitational redshift effect. Observationally, a spectral shift will depend on the stellar mass-to-radius ratio as expected from the theoretical estimation of relativity. After the analysis, the obtained correlation coefficient between theoretical predictions and observations for 28 (51) OCs is a = 0.977 ± 0.218 (0.899 ± 0.137). The result has proven to be statistically robust and with little dependence on the details of the methodology or sample selection criteria. This study represents one of the more extensive validations of a fundamental prediction of gravity theories.

Keywords: Redshifted, Gravitation, Open star clusters, General relativity, Radial velocity
On Estimating the Cosmic Molecular Gas Density from CO Line Intensity Mapping Observations. The Millimeter-wave Intensity Mapping Experiment (mmIME) recently reported a detection of excess spatial fluctuations at a wavelength of 3 mm, which can be attributed to unresolved emission of several CO rotational transitions between z ~ 1 and 5. We study the implications of these data for the high-redshift interstellar medium using a suite of state-of-the-art semianalytic simulations that have successfully reproduced many other submillimeter line observations across the relevant redshift range. We find that the semianalytic predictions are mildly in tension with the mmIME result, with a predicted CO power ~3.5σ below what was observed. We explore some simple modifications to the models that could resolve this tension. Increasing the molecular gas abundance at the relevant redshifts to ~108 M ⊙ Mpc-3, a value well above that obtained from directly imaged sources, would resolve the discrepancy, as would assuming a CO-H2 conversion factor α CO of ~1.5 M ⊙ K-1 (km s-1)-1 pc2, a value somewhat lower than is commonly assumed. We go on to demonstrate that these conclusions are quite sensitive to the detailed assumptions of our simulations, highlighting the need for more careful modeling efforts as more intensity mapping data become available.

Keywords: Surveys, Molecular gas, Galaxy evolution, CO line emission
Relativistic Alfvén Waves Entering Charge-starvation in the Magnetospheres of Neutron Stars. Instabilities in a neutron star can generate Alfvén waves in its magnetosphere. Propagation along the curved magnetic field lines strongly shears the wave, boosting its electric current j A. We derive an analytic expression for the evolution of the wavevector k and the growth of j A. In the strongly sheared regime, j A may exceed the maximum current j 0 that can be supported by the background e ± plasma. We investigate these charge-starved waves, first using a simplified two-fluid analytic model, then with first-principles kinetic simulations. We find that the Alfvén wave is able to propagate successfully even when κ ≡ j A/j 0 ≫ 1. It sustains j A by compressing and advecting the plasma along the magnetic field lines with an increasing Lorentz factor, γ ≳ κ 1/2. The simulations show how plasma instabilities lead to gradual dissipation of the wave energy. Our results suggest that an extremely high charge-starvation parameter κ ≳ 104 may be required in order for this mechanism to power the observed fast radio bursts (FRBs) from SGR 1935+2154. However, cosmological FRBs with much higher luminosities are unlikely to be a result of charge-starvation.

Keywords: Neutron stars, Radio bursts, Plasma physics
Lunar Orbit Measurement of the Cosmic Dawn's 21 cm Global Spectrum. A redshifted 21 cm line absorption signature is commonly expected from the cosmic dawn era, when the first stars and galaxies formed. The detailed traits of this signal can provide important insight on the cosmic history. However, high-precision measurement of this signal is hampered by ionosphere refraction and absorption, as well as radio frequency interference (RFI). Space observation can solve the problem of the ionosphere, and the Moon can shield the RFI from Earth. In this paper, we present simulations of the global spectrum measurement in the 30-120 MHz frequency band on the lunar orbit from the proposed Discovering the Sky at the Longest wavelength project. In particular, we consider how the measured signal varies as the satellite moves along the orbit and take into account the blockage of different parts of the sky by the Moon and the antenna response. We estimate the sensitivity for such a 21 cm global spectrum experiment. An rms noise level of ≤0.05 K is expected at 75 MHz after 10 orbits (~1 day) observation, for a frequency channel width of 0.4 MHz. We also study the influence of a frequency-dependent beam, which may generate complex structures in the spectrum. Estimates of the uncertainties in the foreground and 21 cm model parameters are obtained.

Keywords: Observational cosmology, H I line emission, Radio telescopes, Space telescopes, Reionization
Quantifying Chemical and Kinematical Properties of Galactic Disks. We aim to quantify the chemical and kinematical properties of Galactic disks with a sample of 119,558 giant stars having abundances and 3D velocities taken or derived from the APOGEE DR17 and Gaia EDR3 catalogs. A Gaussian mixture model is employed to distinguish the high-α and low-α sequences along the metallicity by simultaneously using chemical and kinematical data. Four disk components are identified and quantified; they are named the hαmp, hαmr, lαmp, and lαmr disks and correspond to the high-α or low-α, and metal-poor or metal-rich properties. Combined with the spatial and stellar-age information, we confirm that they are well interpreted by the two-infall formation model. The first infall of turbulent gas quickly forms the hot and thick hαmp disk with consequent thinner hαmr and lαmr disks. Then the second gas accretion forms a thinner and outermost lαmp disk. We find that the inside-out and upside-down scenario does not only satisfy the overall Galactic disk formation of these two major episodes but is also presented in the formation sequence of the three inner disks. Importantly, we reveal the inverse age-[M/H] trend of the lαmr disk, which means its younger stars are more metal-poor, indicating that the rejuvenated gas from the second accretion gradually dominates later star formation. Meanwhile, the recently formed stars converge to [M/H] ~ -0.1 dex, demonstrating a sufficient mixture of gas from two infalls.

Keywords: Milky Way formation, Stellar abundances, Galaxy structure, Milky Way dynamics, Astronomy data analysis, Milky Way disk, Galaxy kinematics, Milky Way evolution, Milky Way Galaxy
Virial Clumps in Central Molecular Zone Clouds. CMZoom survey observations with the Submillimeter Array are analyzed to describe the virial equilibrium (VE) and star-forming potential of 755 clumps in 22 clouds in the Central Molecular Zone (CMZ) of the Milky Way. In each cloud, nearly all clumps follow the column density-mass trend N ∝ M  s , where s = 0.38 ± 0.03 is near the pressure-bounded limit s  p  = 1/3. This trend is expected when gravitationally unbound clumps in VE have similar velocity dispersion and external pressure. Nine of these clouds also harbor one or two distinctly more massive clumps. These properties allow a VE model of bound and unbound clumps in each cloud, where the most massive clump has the VE critical mass. These models indicate that 213 clumps have velocity dispersion 1-2 km s-1, mean external pressure (0.5-4) × 108 cm-3 K, bound clump fraction 0.06, and typical virial parameter α = 4-15. These mostly unbound clumps may be in VE with their turbulent cloud pressure, possibly driven by inflow from the Galactic bar. In contrast, most Sgr B2 clumps are bound according to their associated sources and N-M trends. When the CMZ clumps are combined into mass distributions, their typical power-law slope is analyzed with a model of stopped accretion. It also indicates that most clumps are unbound and cannot grow significantly, due to their similar timescales of accretion and dispersal, ~0.2 Myr. Thus, virial and dynamical analyses of the most extensive clump census available indicate that star formation in the CMZ may be suppressed by a significant deficit of gravitationally bound clumps.

Keywords: Galactic center, Star formation, Molecular clouds
ALMA Measures Molecular Gas Reservoirs Comparable to Field Galaxies in a Low-mass Galaxy Cluster at z = 1.3. We report the serendipitous discovery of an overdensity of CO emitters in an X-ray-identified cluster (Log10 M halo/M ☉ ~ 13.6 at z = 1.3188) using ALMA. We present spectroscopic confirmation of six new cluster members exhibiting CO(2-1) emission, adding to two existing optical/IR spectroscopic members undetected in CO. This is the lowest-mass cluster to date at z &gt; 1 with molecular gas measurements, bridging the observational gap between galaxies in the more extreme, well-studied clusters (Log10 M halo/M ☉ ≳ 14) and those in group or field environments at cosmic noon. The CO sources are concentrated on the sky (within ~1 arcmin diameter) and phase space analysis indicates the gas resides in galaxies already within the cluster environment. We find that CO sources sit in similar phase space as CO-rich galaxies in more massive clusters at similar redshifts (have similar accretion histories) while maintaining field-like molecular gas reservoirs, compared to scaling relations. This work presents the deepest CO survey to date in a galaxy cluster at z &gt; 1, uncovering gas reservoirs down to ${M}_{{{\rm{H}}}_{2}}\gt 1.6\times {10}^{10}$ M ☉ (5σ at 50% primary beam). Our deep limits rule out the presence of gas content in excess of the field scaling relations; however, combined with literature CO detections, cluster gas fractions in general appear systematically high, on the upper envelope or above the field. This study is the first demonstration that low-mass clusters at z ~ 1-2 can host overdensities of CO emitters with surviving gas reservoirs, in line with the prediction that quenching is delayed after first infall while galaxies consume the gas bound to the disk.

Keywords: Molecular gas, Galaxy evolution, High-redshift galaxy clusters
A Rich Satellite Population of the NGC 4437 Group and Implications of a Magnitude Gap for Galaxy Group Assembly History. Both observations and cosmological simulations have recently shown that there is a large scatter in the number of satellites of Milky Way (MW)-like galaxies. In this study, we investigate the relation between the satellite number and galaxy group assembly history using the r-band magnitude gap (Δm 12) between the brightest and second-brightest galaxies as an indicator. From 20 deg2 of the Hyper Suprime-Cam Subaru Strategic Program Wide layer, we identify 17 dwarf satellite candidates around NGC 4437, a spiral galaxy with about one-fourth of the MW stellar mass. We estimate their distances using the surface brightness fluctuation method. Then we confirm five candidates as members of the NGC 4437 group, resulting in a total of seven group members. Combining the NGC 4437 group (with Δm 12 = 2.5 mag) with other groups in the literature, we find a stratification of the satellite number by Δm 12 for a given host stellar mass. The satellite number for the given host stellar mass decreases as Δm 12 increases. The same trend is found in simulated galaxy groups in the TNG50 simulation of the IllustrisTNG project. We also find that the host galaxies in groups with a smaller Δm 12 (like NGC 4437) have assembled their halo mass more recently than those in larger gap groups, and that their stellar-to-halo mass ratios increase as Δm 12 increases. These results show that the large scatter in the satellite number is consistent with a large range of Δm 12, indicating diverse group assembly histories.

Keywords: Luminosity function, Galaxy dark matter halos, Galaxy distances, Dwarf galaxies, Distance indicators, Galaxy groups
Is There an Enormous Cold Front at the Virial Radius of the Perseus Cluster?. We present new XMM-Newton observations extending the mosaic of the Perseus cluster out to the virial radius to the west. Previous studies with ROSAT have reported a large excess in surface brightness to the west, possibly the result of large-scale gas sloshing. In our new XMM-Newton observations we have found two X-ray surface brightness edges at 1.2 and 1.7 Mpc to the west. The temperature measurements obtained with Suzaku data indicate that the temperature increases sharply at each edge, consistent with what would be expected from cold fronts. However the the XMM-Newton data are affected by stray light, which at present is a poorly understood source of systematic error that can also lead to curved features in X-ray images. To test our results, we compared our X-ray surface brightness profile with that obtained from ROSAT PSPC data. While the edge at 1.2 Mpc is confirmed by ROSAT PSPC, the ROSAT data quality is insufficient to confirm the outer edge at 1.7 Mpc. Further observations with future X-ray telescopes will be needed to confirm the existence of the outer edge at 1.7 Mpc. By comparing with numerical simulations, we find that these large cold fronts require a large impact parameter, and low-mass ratio mergers that can produce fast gas motions without destroying the cluster core.

Keywords: Galaxy clusters, X-ray astronomy, High energy astrophysics, Intracluster medium, Perseus Cluster