adsabs/SciX_UAT_keywords huggingface dataset:
The Effect of Adiabatic Compression on Dark Matter Halos and the Radial Acceleration Relation

We use a semiempirical model to investigate the radial acceleration relation (RAR) in a cold dark matter (CDM) framework. Specifically, we build 80 model galaxies covering the same parameter space as the observed galaxies in the SPARC database, assigning them to dark matter (DM) halos using abundance-matching and halo mass-concentration relations. We consider several abundance-matching relations, finding some to be a better match to the kinematic data than others. We compute the unavoidable gravitational interactions between baryons and their DM halos, leading to an overall compression of the original Navarro-Frenk-White (NFW) halos. Before halo compression, high-mass galaxies lie approximately on the observed RAR, whereas low-mass galaxies display up-bending "hooks" at small radii due to DM cusps, making them deviate systematically from the observed relation. After halo compression, the initial NFW halos become more concentrated at small radii, making larger contributions to rotation curves. This increases the total accelerations, moving all model galaxies away from the observed relation. These systematic deviations suggest that the CDM model with abundance matching alone cannot explain the observed RAR. Further effects (e.g., feedback) would need to counteract the compression with precisely the right amount of halo expansion, even in high-mass galaxies with deep potential wells where such effects are generally predicted to be negligible.

Keywords: dark matter; galaxy dynamics; galaxy kinematics; spiral galaxies; dwarf galaxies
An Exploration of Three New Methods to Facilitate the Calculation of the Significance Levels of Periodogram Peaks by Simulation

At a given frequency ν, calculation of the periodogram entails evaluating two linear combinations $C(\nu )$ and $S(\nu )$ of the observations. It is pointed out that C and S are normally distributed even for relatively small numbers of observations. This can be used as a basis for simulating periodograms from a multivariate normal distribution with specified covariance structure. The advantage is that computationally expensive evaluations of sinusoids need to be performed only once—in the calculation of the covariances. Furthermore, the large covariance matrix can be factorized, and the factors replaced by low-rank approximations, which alleviates the computer memory demands. The second part of the paper discusses the choice of the degree of oversampling of the periodogram, i.e., the spacing ${\rm{\Delta }}\nu $ of the frequency grid over which it is calculated. It is shown using ${\rm{\Delta }}\nu \sim 0.2/{\rm{\Delta }}T$ , where ΔT is the time baseline of the observations, leads to an error of only about 1% in the percentiles of the distribution of maximum peak values. The third part of the paper deals with the representation of the distribution of periodogram maxima by the generalized extreme value distribution. Although the generalized extreme value form may formally differ highly significantly from the actual distribution of periodogram maxima, it is demonstrated that it may nonetheless be useful in practical terms. Results are illustrated throughout using three data sets with widely different aliasing properties.

Keywords: time series analysis
A New Stellar Companion to GJ 1292

I present the discovery of a new stellar companion to GJ 1292 detected with the NN-EXPLORE Exoplanet and Stellar Speckle Imager at the 3.5 m WIYN Telescope. The companion was detected at an angular separation of 0.″1244, a position angle of 44°, and a delta magnitude of 0.97 at 832 nm. I also estimate a projected separation of 2.09 au, a mass ratio of 0.69, and component spectral types of M2.5 and M3.

Keywords: binary stars; visual binary stars; close binary stars; m dwarf stars; speckle interferometry; high angular resolution; low mass stars
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] < -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 <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
Diffusive Hydrogenation Reactions of CO Embedded in Amorphous Solid Water at Elevated Temperatures ∼70 K

The surface processes on interstellar dust grains have an important role in the chemical evolution in molecular clouds. Hydrogenation reactions on ice surfaces have been extensively investigated and are known to proceed at low temperatures mostly below 20 K. In contrast, information about the chemical processes of molecules within an ice mantle is lacking. In this work, we investigated diffusive hydrogenation reactions of carbon monoxide (CO) embedded in amorphous solid water (ASW) as a model case and discovered that the hydrogenation of CO efficiently proceeds to yield H2CO and CH3OH even above 20 K when CO is buried beneath ASW. The experimental results suggest that hydrogen atoms diffuse through the cracks of ASW and have a sufficient residence time to react with embedded CO. The hydrogenation reactions occurred even at temperatures up to ∼70 K. Cracks collapse at elevated temperatures but the occurrence of hydrogenation reactions means that the cracks would not completely disappear and remain large enough for penetration by hydrogen atoms. Considering the hydrogen-atom fluence in the laboratory and molecular clouds, we suggest that the penetration of hydrogen and its reactions within the ice mantle occur in astrophysical environments.

Keywords: astrochemistry; molecular clouds; dense interstellar clouds; interstellar molecules; interstellar dust; laboratory astrophysics
The Properties of the Interstellar Medium of Galaxies across Time as Traced by the Neutral Atomic Carbon [C I]

We report Atacama Large Millimeter Array observations of the neutral atomic carbon transitions [C I] and multiple CO lines in a sample of ∼30 main-sequence galaxies at $z\sim 1$ , including novel information on [C I] ${(}^{3}{P}_{2}{\mbox{--}}^{3}{P}_{1})$ and CO $(7\mbox{--}6)$ for 7 of such normal objects. We complement our observations with a collection of >200 galaxies with coverage of similar transitions, spanning the z = 0-4 redshift interval and a variety of ambient conditions from local to high-redshift starbursts. We find systematic variations in the [C I]/IR and [C I]/high-Jupper (Jupper = 7) CO luminosity ratios among the various samples. We interpret these differences as increased dense molecular gas fractions and star formation efficiencies in the strongest high-redshift starbursts with respect to normal main-sequence galaxies. We further report constant ${L}_{{[{\rm{C}}{\rm{I}}]}^{3}{P}_{2}\,-{}^{3}{P}_{1}}^{{\prime} }$ / ${L}_{{[{\rm{C}}{\rm{I}}]}^{3}{P}_{1}\,-{}^{3}{P}_{0}}^{{\prime} }$ ratios across the galaxy populations and redshifts, suggesting that gas temperatures Texc traced by [C I] do not strongly vary. We find only a mild correlation with Tdust and that, generally, Texc ≲ Tdust. We fit the line ratios with classical photodissociation region models, retrieving consistently larger densities and intensities of the UV radiation fields in submillimeter galaxies than in main-sequence and local objects. However, these simple models fall short in representing the complexity of a multiphase interstellar medium and should be treated with caution. Finally, we compare our observations with the Santa Cruz semi-analytical model of galaxy evolution, recently extended to simulate submillimeter emission. While we confirm the success in reproducing the CO lines, we find systematically larger [C I] luminosities at fixed IR luminosity than predicted theoretically. This highlights the necessity of improving our understanding of the mechanisms regulating the [C I] emission on galactic scales. We release our data compilation to the community.

Keywords: galaxy evolution; high-redshift galaxies; starburst galaxies; ultraluminous infrared galaxies; submillimeter astronomy; interstellar medium; star formation
Statistical Properties of Small-scale Linear Magnetic Holes in the Martian Magnetosheath

The small-scale linear magnetic hole (LMH) is a magnetic dip with a size less than or on the order of ρi (proton gyroradius), which may contribute to turbulence properties in the solar wind and other astrophysical plasmas. Based on one-month measurements of the Mars Atmosphere and Volatile EvolutioN mission, 174 small-scale LMH events in the Martian magnetosheath are used to investigate their statistical properties in this study. Our results show that small-scale linear LMHs are ubiquitous in the Martian magnetosheath, and their occurrence rate is estimated to be approximately 1.5 events per hour based on one-month observations. Compared with the ambient plasma, the averaged magnitude of the magnetic field in these holes can decrease from 6.8-3.5 nT. Nearly 66% of events have a Bmin/B value in the range of (0.45, 0.75). The duration of small-scale MHs is mainly less than 0.4 s. For 90% of the events, the size along the solar wind flow is less than ρi. As the rotation angle increases, the occurrence rate of small-scale LMHs decrease. However, the Bmin/B, size, and duration of small-scale LMHs have no obvious dependence on their rotation angle.

Keywords: mars; space plasmas
A Monte Carlo Simulation on Resonant Scattering of X-Ray Line Emission in Supernova Remnants

Resonant scattering (RS) of X-ray line emission in supernova remnants (SNRs) may modify the observed line profiles and fluxes and has a potential impact on estimating the physical properties of the hot gas and hence on understanding the SNR physics, but has not been theoretically modeled ever. Here we present our Monte Carlo simulation of the RS effect on X-ray resonant-line emission, typified by the O VII Heα r line, from SNRs. We employ the physical conditions characterized by the Sedov–Taylor solution and some basic parameters similar to those in Cygnus Loop. We show that the impact of the RS effect is most significant near the edge of the remnant. The line profiles are predicted to be asymmetric because of different temperatures and photon production efficiencies of the expanding gas at different radii. We also predict the surface brightness of the line emission would decrease in the outer projected region but is slightly enhanced in the inner. The G-ratio of the O VII Heα triplet can be effectively elevated by RS in the outer region. We show that the RS effect of the O VII Heα r line in the southwestern boundary region of Cygnus Loop is nonnegligible. The observed O VII G-ratio of ∼1.8 of the region could be achieved with RS taken into account for properly elevated O abundance from the previous estimates. Additional simulation performed for the SNRs in ejecta-dominated phases like Cas A shows that RS in the shocked ejecta may have some apparent effects on the observational properties of oxygen-resonant lines.

Keywords: radiative transfer; supernova remnants; x-ray astronomy; atomic spectroscopy
Blueshifted Hydrogen Emission and Shock Wave of RR Lyrae Variables in SDSS and LAMOST

Hydrogen emissions of RR Lyrae variables are the imprints of shock waves traveling through their atmospheres. We develop a pattern recognition algorithm, which is then applied to single-epoch spectra of the Sloan Digital Sky Survey and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey. These two spectroscopic surveys covered ~10,000 photometrically confirmed RR Lyrae stars. We discovered in total 127 RR Lyrae stars with blueshifted Balmer emission features, including 103 fundamental mode (RRab), 20 first-overtone (RRc), 3 double-mode (RRd), and 1 Blazhko-type (temporary classification for RR Lyrae stars with strong Blazhko modulation in the Catalina sky survey that cannot be characterized) RR Lyrae variable. This forms the largest database to date of the properties of hydrogen emission in RR Lyrae variables. Based on Zwicky Transient Facility DR5, we carried out a detailed light-curve analysis for the Blazhko-type RR Lyrae star with hydrogen emission of long-term modulations. We characterize the Blazhko-type RR Lyrae star as an RRab and point out a possible Blazhko period. Finally, we set up simulations on mock spectra to test the performance of our algorithm and on the real observational strategy to investigate the occurrence of the "first apparition."

Keywords: rr lyrae variable stars; shocks; blazhko effect; stellar atmospheres; spectroscopy; astronomy databases
Spatial and Binary Parameter Distributions of Black Hole Binaries in the Milky Way Detectable with Gaia

Soon after Gaia Data Release 3 (DR3) in 2022 June, some candidates (and one confirmed) of detached black hole (BH)-luminous companion (LC) binaries have been reported. Existing and future detections of astrometric BH-LC binaries will shed light on the spatial distribution of these systems, which can deepen our understanding of the natal kicks and the underlying formation mechanism of BHs. By tracking Galactic orbits of BH-LC binaries obtained from BSE, we find that distributions of BH mass and the height from the Galactic plane ∣z∣ would help us give a constraint on the supernova model. We also indicate that the correlations of (i) orbital periods and eccentricities, and (ii) BH mass and ∣z∣ could be clues for the strength of the natal kick, and that the correlations of (P, Z/Z ⊙) may give us a clue for the common-envelope (CE) efficiency. We also discuss the possibility of forming BH-LC binaries like the BH binary candidates reported in Gaia DR3 and Gaia BH 1, finding that if the candidates as well as the confirmed binary originate from isolated binaries, they favor models that produce low-mass BHs and have high CE efficiencies exceeding unity.

Keywords: astrometry; black holes; astrometric binary stars
OGLE-2018-BLG-1185b: A Low-mass Microlensing Planet Orbiting a Low-mass Dwarf

We report an analysis of the planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the Spitzer Space Telescope. The ground-based light curve indicates a low planet-host star mass ratio of q = (6.9 ± 0.2) × 10-5, which is near the peak of the wide-orbit exoplanet mass-ratio distribution. We estimate the host star and planet masses with a Bayesian analysis using the measured angular Einstein radius under the assumption that stars of all masses have an equal probability of hosting the planet. The flux variation observed by Spitzer is marginal, but still places a constraint on the microlens parallax. Imposing a conservative constraint that this flux variation should be ΔfSpz < 4 instrumental flux units yields a host mass of ${M}_{\mathrm{host}}={0.37}_{-0.21}^{+0.35}\ {M}_{\odot }$ and a planet mass of ${m}_{{\rm{p}}}={8.4}_{-4.7}^{+7.9}\ {M}_{\oplus }$. A Bayesian analysis including the full parallax constraint from Spitzer suggests smaller host star and planet masses of ${M}_{\mathrm{host}}={0.091}_{-0.018}^{+0.064}\ {M}_{\odot }$ and ${m}_{{\rm{p}}}={2.1}_{-0.4}^{+1.5}\ {M}_{\oplus }$, respectively. Future high-resolution imaging observations with the Hubble Space Telescope or Extremely Large Telescope could distinguish between these two scenarios and help reveal the planetary system properties in more detail.

Keywords: gravitational microlensing; gravitational microlensing exoplanet detection; satellite microlensing parallax
Distributions and Physical Properties of Molecular Clouds in the Third Galactic Quadrant: l = [219.°75, 229.°75] and b = [-5.°25, 5.°25]

We present the results of an unbiased 12CO/13CO/C18O (J = 1-0) survey in a portion of the third Galactic quadrant (TGQ): 219.°75 ≤ l ≤ 229.°75 and -5.°25 ≤ b ≤ 5.°25. The high-resolution and high-sensitivity data sets help to unravel the distributions and physical properties of the molecular clouds (MCs) in the mapped area. In the LSR velocity range from ~-1 to ~85 km s-1, the molecular material successfully traces the Local, Perseus, and Outer arms. In the TGQ, the Outer arm appears to be more prominent than that in the second Galactic quadrant (SGQ), but the Perseus arm is not as conspicuous as that in the SGQ. A total of 1,502 12CO, 570 13CO, and 53 C18O molecular structures are identified, spanning over ~2 and ~6 orders of magnitude in size and mass, respectively. Tight mass-radius correlations and virial parameter-mass anticorrelations are observable. Yet, it seems that no clear correlations between velocity dispersion and effective radius can be found over the full dynamic range. The vertical distribution of the MCs renders evident pictures of the Galactic warp and flare.

Keywords: interstellar molecules; co line emission; molecular clouds; spiral arms
Black Hole Gravitational Potential Enhanced Fallback Accretion onto the Nascent Lighter Compact Object: Tentative Evidence in the O3 Run Data of LIGO/Virgo

In a binary system, the gravitational potential of the primary black hole may play an important role in enhancing the fallback accretion onto the lighter compact object newly formed in the second supernova explosion. As a result, the final masses of the binary compact objects would be correlated, as suggested recently by Safarzadeh & Wysocki. In this work, we analyze the mass distribution of four gravitational-wave events, which are characterized by both a small mass ratio and a low mass (≤5M&CircleDot;) of the light component, and find tentative evidence for a mass correlation among the objects. To evaluate the feasibility of testing such a hypothesis with upcoming observations, we carry out simulations with a mock population and perform Bayesian hierarchical inference for the mass distribution. We find that with dozens of low mass ratio events, whether there exists correlation in the component mass distributions or not can be robustly tested and the correlation, if it exists, can be well determined.

Keywords: gravitational wave sources; compact objects
Performance Enhancement of Tree-based Friends-of-friends Galaxy Finder for High-resolution Simulations of Galaxy Formation

Cosmological simulations are useful tools for studying the evolution of galaxies, and it is critical to accurately identify galaxies and their halos from raw simulation data. The friends-of-friends (FoF) algorithm has been widely adopted for this purpose because of its simplicity and expandability to higher dimensions. However, it is cost-inefficient when applied to high-resolution simulations because standard FoF implementation leads to too many distance calculations in dense regions. We confirm this through our exercise of applying the six-dimensional (6D) FoF galaxy finder code, VELOCIRAPTOR, on the NEWHORIZON simulation. The high particle resolution of NEWHORIZON (M star ~ 104 M ⊙) allows a large central number density (106 kpc-3) for typical galaxies, resulting in a few days to weeks of galaxy searches for just one snapshot. Even worse, we observed a significant decrease in the FoF performance in the high-dimensional 6D searches: "the curse of dimensionality" problem. To overcome these issues, we have developed several implementations that can be readily applied to any tree-based FoF code. They include limiting visits to tree nodes, reordering the list of particles for searching neighbor particles, and altering the tree structure. Compared to the run with the original code, the new run with these implementations results in the identical galaxy detection with the ideal performance, $O(N\mathrm{log}N)$ , N being the number of particles in a galaxy-with a speed gain of a factor of 2700 in 3D or 12 in a 6D FoF search.

Keywords: astronomy software
Likely Detection of GeV Gamma-Ray Emission from the Composite Supernova Remnant COMP G327.1+1.1 with Fermi-LAT

We report the likely GeV γ-ray emission from the composite supernova remnant (SNR) COMP G327.1+1.1 by analyzing ∼12.2 yr of the Fermi Large Area Telescope (Fermi-LAT) Pass 8 data. We found the features of its spectrum and luminosity are well consistent with those of the observed COMP SNRs in the Milky Way. Moreover, the position of the source matches those in radio and TeV energy bands; we propose that the γ-ray source is likely to be a GeV counterpart of COMP G327.1+1.1. Considering the case of the association from COMP G327.1+1.1 and the γ-ray source, we interpreted its broadband spectral energy distribution (SED) by using three simple stationary models including one-zone and two-zone leptonic models and a one-zone leptohadronic model. We found that the simple two-zone model dominated by leptons can better explain its SED. More high-energy data are expected to firmly confirm the association between the γ-ray source and COMP G327.1+1.1 in the future.

Keywords: gamma-ray astronomy; non-thermal radiation sources; supernova remnants; diffuse nebulae