adsabs/SciX_UAT_keywords huggingface dataset:
Wave Composition, Propagation, and Polarization of Magnetohydrodynamic Turbulence within 0.3 au as Observed by Parker Solar Probe

Turbulence, a ubiquitous phenomenon in interplanetary space, is crucial for the energy conversion of space plasma at multiple scales. This work focuses on the propagation, polarization, and wave composition properties of the solar wind turbulence within 0.3 au, and its variation with heliocentric distance at magnetohydrodynamic scales (from 10 s to 1000 s in the spacecraft frame). We present the probability density function of propagation wavevectors (PDF (k∥, k⊥)) for solar wind turbulence within 0.3 au for the first time: (1) wavevectors cluster quasi-(anti-)parallel to the local background magnetic field for kdi < 0.02, where di is the ion inertial length; (2) wavevectors shift to quasi-perpendicular directions for kdi > 0.02. Based on our wave composition diagnosis, we find that: the outward/anti-sunward Alfvén mode dominates over the whole range of scales and distances, the spectral energy density fraction of the inward/sunward fast mode decreases with distance, and the fractional energy densities of the inward and outward slow mode increase with distance. The outward fast mode and inward Alfvén mode represent minority populations throughout the explored range of distances and scales. On average, the degree of anisotropy of the magnetic fluctuations defined with respect to the minimum variation direction decreases with increasing scale, with no trend in distance at any scale. Our results provide comprehensive insight into the scenario of transport and transfer of the solar wind fluctuations/turbulence in the inner heliosphere.

Keywords: heliosphere; alfven waves; slow solar wind; interplanetary turbulence
The Effects of Radiative Feedback and Supernova-induced Turbulence on Early Galaxies

The recently launched James Webb Space Telescope promises unparalleled advances in our understanding of the first stars and galaxies, but realizing this potential requires cosmological simulations that capture the key physical processes that affected these objects. Here, we show that radiative transfer and subgrid turbulent mixing are two such processes. By comparing simulations with and without radiative transfer but with exactly the same physical parameters and subgrid turbulent mixing model, we show that tracking radiative transfer suppresses the Population III star formation density by a factor ≈4. In both simulations, ≳90% of Population III stars are found in the unresolved pristine regions tracked by our subgrid model, which does a better job at modeling the regions surrounding proto-galaxy cores where metals from supernovae take tens of megayears to mix thoroughly. At the same time, radiative transfer suppresses Population III star formation, via the development of ionized bubbles that slow gas accretion in these regions, and it results in compact high-redshift galaxies that are surrounded by isolated low-mass satellites. Thus, turbulent mixing and radiative transfer are both essential processes that must be included to accurately model the morphology, composition, and growth of primordial galaxies.

Keywords: radiative transfer simulations; hydrodynamical simulations; galaxy formation; population iii stars; early universe; early astronomical instruments
Planck Cold Clumps in the λ Orionis Complex. III. A Chemical Probe of Stellar Feedback on Cores in the λ Orionis Cloud

Massive stars have a strong impact on their local environments. However, how stellar feedback regulates star formation is still under debate. In this context, we studied the chemical properties of 80 dense cores in the Orion molecular cloud complex composed of the Orion A (39 cores), B (26 cores), and λ Orionis (15 cores) clouds using multiple molecular line data taken with the Korean Very Long Baseline Interferometry Network 21 m telescopes. The λ Orionis cloud has an H II bubble surrounding the O-type star λ Ori, and hence it is exposed to the ultraviolet (UV) radiation field of the massive star. The abundances of C2H and HCN, which are sensitive to UV radiation, appear to be higher in the cores in the λ Orionis cloud than in those in the Orion A and B clouds, while the HDCO to H2CO abundance ratios show the opposite trend, indicating warmer conditions in the λ Orionis cloud. The detection rates of dense gas tracers such as the N2H+, HCO+, and H13CO+ lines are also lower in the λ Orionis cloud. These chemical properties imply that the cores in the λ Orionis cloud are heated by UV photons from λ Ori. Furthermore, the cores in the λ Orionis cloud do not show any statistically significant excess in the infall signature of HCO+ (1-0), unlike those in the Orion A and B clouds. Our results support the idea that feedback from massive stars impacts star formation in a negative way by heating and evaporating dense materials, as in the λ Orionis cloud.

Keywords: star formation; stellar feedback; interstellar medium; molecular clouds; photodissociation regions; h ii regions; chemical abundances
A Classification Catalog of Periodic Variable Stars for LAMOST DR9 Based on Machine Learning

Identifying and classifying variable stars is essential to time-domain astronomy. The Large Area Multi-Object Fiber Optic Spectroscopic Telescope (LAMOST) acquired a large amount of spectral data. However, there is no corresponding variable source-related information in the data, constraining LAMOST data utilization for scientific research. In this study, we systematically investigated variable source classification methods for LAMOST data. We constructed a 10-class classification model using three mainstream machine-learning methods. Through performance comparison, we chose the LightGBM and XGBoost models. We further identified variable source candidates in the r band in LAMOST DR9 and obtained 281,514 variable source candidates with probabilities greater than 95%. Subsequently, we filtered out the sources of periodic variable sources using the generalized Lomb–Scargle periodogram and classified these periodic variable sources using the classification model. Finally, we propose a reliable periodic variable star catalog containing 176,337 stars with specific types.

Keywords: catalogs; variable stars; cross-validation; light curves
Absence of Bursts between 4 and 8 GHz from FRB 20200120E Located in an M81 Globular Cluster

We report the non-detection of dispersed bursts between 4 and 8 GHz from 2.5 hr of observations of FRB 20200120E at 6 GHz using the Robert C. Byrd Green Bank Telescope. Our fluence limits are several times lower than the average burst fluences reported at 600 and 1400 MHz. We conclude that these non-detections are either due to high-frequency bursts being weaker and/or scintillation-induced modulated. It is also likely that our observations were non-concurrent with any activity window of FRB 20200120E.

Keywords: radio transient sources
The Magnesium Isotope Composition of Samples Returned from Asteroid Ryugu

The nucleosynthetic isotope composition of planetary materials provides a record of the heterogeneous distribution of stardust within the early solar system. In 2020 December, the Japan Aerospace Exploration Agency Hayabusa2 spacecraft returned to Earth the first samples of a primitive asteroid, namely, the Cb-type asteroid Ryugu. This provides a unique opportunity to explore the kinship between primitive asteroids and carbonaceous chondrites. We report high-precision μ 26Mg* and μ 25Mg values of Ryugu samples together with those of CI, CM, CV, and ungrouped carbonaceous chondrites. The stable Mg isotope composition of Ryugu aliquots defines μ 25Mg values ranging from -160 ± 20 ppm to -272 ± 30 ppm, which extends to lighter compositions relative to Ivuna-type (CI) and other carbonaceous chondrite groups. We interpret the μ 25Mg variability as reflecting heterogeneous sampling of a carbonate phase hosting isotopically light Mg (μ 25Mg ~ -1400 ppm) formed by low temperature equilibrium processes. After correcting for this effect, Ryugu samples return homogeneous μ 26Mg* values corresponding to a weighted mean of 7.1 ± 0.8 ppm. Thus, Ryugu defines a μ 26Mg* excess relative to the CI and CR chondrite reservoirs corresponding to 3.8 ± 1.1 and 11.9 ± 0.8 ppm, respectively. These variations cannot be accounted for by in situ decay of 26Al given their respective 27Al/24Mg ratios. Instead, it requires that Ryugu and the CI and CR parent bodies formed from material with a different initial 26Al/27Al ratio or that they are sourced from material with distinct Mg isotope compositions. Thus, our new Mg isotope data challenge the notion that Ryugu and CI chondrites share a common nucleosynthetic heritage.

Keywords: solar system evolution; asteroids; carbonaceous chondrites; meteorite composition; nucleosynthesis
The Origin of Low-redshift Event Rate Excess as Revealed by the Low-luminosity Gamma-Ray Bursts

The relation between the event rate of long gamma-ray bursts and the star formation rate is still controversial, especially at the low-redshift end. Dong et al. confirmed that the gamma-ray burst rate always exceeds the star formation rate at a low redshift of z < 1 in spite of the sample completeness. However, the reason for low-redshift excess is still unclear. Since low-luminosity bursts are at smaller redshifts generally, we choose three Swift long burst samples and classify them into low- and high-luminosity bursts in order to check whether the low-redshift excess is existent and if the excess is biased by the sample size and completeness. To degenerate the redshift evolution from luminosity, we adopt the nonparametric method to study the event rate of the two types of long bursts in each sample. It is found that the high-luminosity burst rate is consistent with the star formation rate within the whole redshift range, while the event rate of low-luminosity bursts exceeds the star formation rate at a low redshift of z < 1. Consequently, we conclude that the low-redshift excess is contributed by the low-luminosity bursts with possibly new origins unconnected with the star formation, which is also independent of the sample size and the sample completeness.

Keywords: gamma-ray bursts
Peeking Between the Pulses: The Far-UV Spectrum of the Previously Unseen White Dwarf in AR Scorpii

The compact object in the interacting binary AR Sco has widely been presumed to be a rapidly rotating, magnetized white dwarf (WD), but it has never been detected directly. Isolating its spectrum has proven difficult because the spin-down of the WD generates pulsed synchrotron radiation that far outshines the WD's photosphere. As a result, a previous study of AR Sco was unable to detect the WD in the averaged far-ultraviolet spectrum from a Hubble Space Telescope (HST) observation. In an effort to unveil the WD's spectrum, we reanalyze these HST observations by calculating the average spectrum in the troughs between synchrotron pulses. We identify weak spectral features from the previously unseen WD and estimate its surface temperature to be 11,500 ± 500 K. Additionally, during the synchrotron pulses, we detect broad Lyα absorption consistent with hot WD spectral models. We infer the presence of a pair of hotspots, with temperatures between 23,000 and 28,000 K, near the magnetic poles of the WD. As the WD is not expected to be accreting from its companion, we describe two possible mechanisms for heating the magnetic poles. The Lyα absorption of the hotspots appears relatively undistorted by Zeeman splitting, constraining the WD's field strength to be ≲100 MG, but the data are insufficient to search for the subtle Zeeman splits expected at lower field strengths.

Keywords: white dwarf stars; cataclysmic variable stars; rotation powered pulsars; magnetic variable stars; dq herculis stars
Mapping Dark Matter with Extragalactic Stellar Streams: The Case of Centaurus A

In the coming decade, thousands of stellar streams will be observed in the halos of external galaxies. What fundamental discoveries will we make about dark matter from these streams? As a first attempt to look at these questions, we model Magellan/Megacam imaging of the Centaurus A (Cen A) disrupting dwarf companion Dwarf 3 (Dw3) and its associated stellar stream, to find out what can be learned about the Cen A dark matter halo. We develop a novel external galaxy stream-fitting technique and generate model stellar streams that reproduce the stream morphology visible in the imaging. We find that there are many viable stream models that fit the data well, with reasonable parameters, provided that Cen A has a halo mass larger than M 200 > 4.70 × 1012 M ⊙. There is a second stream in Cen A's halo that is also reproduced within the context of this same dynamical model. However, stream morphology in the imaging alone does not uniquely determine the mass or mass distribution for the Cen A halo. In particular, the stream models with high likelihood show covariances between the inferred Cen A mass distribution, the inferred Dw3 progenitor mass, the Dw3 velocity, and the Dw3 line-of-sight position. We show that these degeneracies can be broken with radial-velocity measurements along the stream, and that a single radial velocity measurement puts a substantial lower limit on the halo mass. These results suggest that targeted radial-velocity measurements will be critical if we want to learn about dark matter from extragalactic stellar streams.

Keywords: galaxy dynamics; dark matter; stellar streams; galaxy structure; galaxy dark matter halos; galaxy stellar halos
Evolutions of Young Type Ia Supernova Remnants with Two Initial Density Profiles in a Turbulent Medium

The expansion index and relative contact discontinuity positions of young type Ia supernova remnants (SNRs) evolving in a turbulent medium are investigated via implementing two-dimensional cylindrical magnetohydrodynamic simulations. In our simulations, two kinds of initial ejecta density profiles are considered: a power-law (PL) profile and an exponential (Exp) profile; large-scale density and magnetic field fluctuations are calculated and mapped into the computational domain before the simulations; the back reaction of the accelerated particles is mimicked through a time-dependent effective adiabatic index γeff(n, t). Our simulation results reveal that the density distributions and magnetic field structures have similar results for both initial profiles. Concerning the expansion index, both the PL and Exp profiles exhibit significant azimuthal variations along the remnant periphery, while the Exp profile manifests itself in a quick path down to the Sedov value as time proceeds. The derived expansion index distributions with both initial profiles are compatible with observations of two typical young type Ia SNRs: SN 1006 and Tycho. As for the relative contact discontinuity positions, when γeff(n, t) works, the derived profiles of both scenarios are globally compatible with the observations despite some deviations. Besides, there are no obvious ejecta protrusions beyond the forward shock, with a lowest derived ratio reaching ∼1.01-1.02 for both initial profiles. Moreover, for purposes of comparison, we have also considered two supplementary scenarios: (1) the aforementioned two density profiles expanding in a homogeneous medium, and (2) a uniform ejecta profile evolving in a turbulent medium.

Keywords: interstellar medium; supernova remnants
Calibrating Mg II-based Black Hole Mass Estimators Using Low-to-high-luminosity Active Galactic Nuclei

We present single-epoch black hole mass (MBH) estimators based on the rest-frame ultraviolet (UV) Mg II 2798 Å and optical Hβ 4861 Å emission lines. To enlarge the luminosity range of active galactic nuclei (AGNs), we combine the 31 reverberation-mapped AGNs with relatively low luminosities from Bahk et al., 47 moderate-luminosity AGNs from Woo et al., and 425 high-luminosity AGNs from the Sloan Digital Sky Survey. The combined sample has a monochromatic luminosity at 5100 Å in the range $\mathrm{log}\lambda {L}_{5100}\sim 41.3\mbox{--}46.5$ erg s-1, over the range 5.5 < log(MBH/M⊙) < 9.5. Based on the fiducial mass from the line dispersion or FWHM of Hβ paired with the continuum luminosity at 5100 Å, we calibrate the best-fit parameters in the black hole mass estimators using the Mg II line. We find that the differences in the line profiles between Mg II and Hβ have significant effects on calibrating the UV MBH estimators. By exploring the systematic discrepancy between the UV and optical MBH estimators as a function of AGN properties, we suggest adding a correction term ${\rm{\Delta }}M=-1.44\,{\rm{log}}({{\rm{FWHM}}}_{{\rm{MgII}}}/{\sigma }_{{\rm{MgII}}})+0.33$ in the equation for the UV mass estimator. We also find a ∼0.1 dex bias in the MBH estimation due to the difference in the spectral slope in the range 2800-5200 Å. Depending on whether the selection of MBH estimator is based on either line dispersion or FWHM and either continuum or line luminosity, the derived UV mass estimators show ≳0.1 dex intrinsic scatter with respect to the fiducial Hβ-based MBH.

Keywords: active galactic nuclei; active galaxies; black holes
A Tight Correlation between Millimeter and X-Ray Emission in Accreting Massive Black Holes from <100 mas Resolution ALMA Observations

Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGNs) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously observed in accreting black holes. We present the results of a dedicated high-spatial-resolution (~60-100 mas) Atacama Large Millimeter/submillimeter Array (ALMA) campaign on a volume-limited (<50 Mpc) sample of 26 hard X-ray (>10 keV) selected radio-quiet AGNs. We find an extremely high detection rate (25/26 or ${94}_{-6}^{+3} \% $ ), which shows that nuclear emission at millimeter wavelengths is nearly ubiquitous in accreting SMBHs. Our high-resolution observations show a tight correlation between the nuclear (1-23 pc) 100 GHz and the intrinsic X-ray emission (1σ scatter of 0.22 dex). The ratio between the 100 GHz continuum and the X-ray emission does not show any correlation with column density, black hole mass, Eddington ratio, or star formation rate, which suggests that the 100 GHz emission can be used as a proxy of SMBH accretion over a very broad range of these parameters. The strong correlation between 100 GHz and X-ray emission in radio-quiet AGNs could be used to estimate the column density based on the ratio between the observed 2-10 keV ( ${F}_{2\mbox{--}10\,\mathrm{keV}}^{\mathrm{obs}}$ ) and 100 GHz (F 100 GHz) fluxes. Specifically, a ratio $\mathrm{log}({F}_{2\mbox{--}10\,\mathrm{keV}}^{\mathrm{obs}}/{F}_{100\,\mathrm{GHz}})\leqslant 3.5$ strongly suggests that a source is heavily obscured ( $\mathrm{log}({N}_{{\rm{H}}}/{\mathrm{cm}}^{-2})\gtrsim 23.8$ ). Our work shows the potential of ALMA continuum observations to detect heavily obscured AGNs (up to an optical depth of one at 100 GHz, i.e., N H ≃ 1027 cm-2), and to identify binary SMBHs with separations <100 pc, which cannot be probed by current X-ray facilities.

Keywords: active galactic nuclei; x-ray active galactic nuclei; supermassive black holes
Variable Accretion onto Protoplanet Host Star PDS 70

The PDS 70 system has been subject to many studies in the past year following the discovery of two accreting planets in the gap of its circumstellar disk. Nevertheless, the mass accretion rate onto the star is still not well known. Here, we determined the stellar mass accretion rate and its variability based on Transiting Exoplanet Survey Satellite and High-Accuracy Radial velocity Planetary Searcher (HARPS) observations. The stellar light curve shows a strong signal with a 3.03 ± 0.06 days period, which we attribute to stellar rotation. Our analysis of the HARPS spectra shows a rotational velocity of V sin I=16.0± 0.5 km s-1, indicating that the inclination of the rotation axis is 50° ± 8°. This implies that the rotation axes of the star and its circumstellar disk are parallel within the measurement error. We apply magnetospheric accretion models to fit the profiles of the Hα line and derive mass accretion rates onto the star in the range of (0.6-2.2)× 10-10 M⊙ yr-1, varying over the rotation phase. The measured accretion rates are in agreement with those estimated from near-UV fluxes using accretion shock models. The derived accretion rates are higher than expected from the disk mass and planets' properties for the low values of the viscous parameter α suggested by recent studies, potentially pointing to an additional mass reservoir in the inner disk to feed the accretion, such as a dead zone. We find that the He I λ10830 line shows a blueshifted absorption feature, indicative of a wind. The mass-loss rate estimated from the line depth is consistent with an accretion-driven inner disk MHD wind.

Keywords: stellar accretion; accretion; protoplanetary disks; h i line emission; t tauri stars
The ELM Survey South. I. An Effective Search for Extremely Low Mass White Dwarfs

We begin the search for extremely low mass (M ≤ 0.3M⊙, ELM) white dwarfs (WDs) in the southern sky based on photometry from the VST ATLAS and SkyMapper surveys. We use a similar color selection method as the Hypervelocity star survey. We switched to an astrometric selection once Gaia Data Release 2 became available. We use the previously known sample of ELM white dwarfs to demonstrate that these objects occupy a unique parameter space in parallax and magnitude. We use the SOAR 4.1 m telescope to test the Gaia-based selection, and identify more than two dozen low mass white dwarfs, including six new ELM white dwarf binaries with periods as short as 2 h. The better efficiency of the Gaia-based selection enables us to extend the ELM Survey footprint to the southern sky. We confirm one of our candidates, J0500-0930, to be the brightest (G = 12.6 mag) and closest (d = 72 pc) ELM white dwarf binary currently known. Remarkably, the Transiting Exoplanet Survey Satellite (TESS) full-frame imaging data on this system reveals low-level (<0.1%) but significant variability at the orbital period of this system (P = 9.5 hr), likely from the relativistic beaming effect. TESS data on another system, J0642-5605, reveals ellipsoidal variations due to a tidally distorted ELM WD. These demonstrate the power of TESS full-frame images in confirming the orbital periods of relatively bright compact object binaries.

Keywords: white dwarf stars; spectroscopy; radial velocity; compact objects
PROBES. I. A Compendium of Deep Rotation Curves and Matched Multiband Photometry

We present the Photometry and Rotation Curve Observations from Extragalactic Surveys (PROBES) compendium of extended rotation curves for 3163 late-type spirals, with matching homogeneous multiband photometry for 1677 of them. PROBES rotation curves originally extracted from Hα long-slit spectra and aperture synthesis H I (21cm) velocity maps typically extend out to a median 2 R e (or 1 R 23.5,r ). Our uniform photometry takes advantage of GALEX, DESI-LIS, and WISE images and the software AutoProf to yield multiband azimuthally averaged surface brightness profiles that achieve depths greater than 25 mag arcsec‑2 (FUV, NUV), 27 mag arcsec‑2 (g, r), and 26 mag arcsec‑2 (z, W1, and W2). With its library of spatially resolved profiles and an extensive table of structural parameters, the versatile PROBES data set will benefit studies of galaxy structure and formation.

Keywords: disk galaxies; galaxy physics; galaxy photometry; galaxy kinematics; galaxy structure; catalogs