adsabs/SciX_UAT_keywords huggingface dataset:
Stellar Atmospheric Parameters for Cool Dwarfs in Gaia Data Release 3

We provide a catalog of atmospheric parameters for 1,806,921 cool dwarfs from Gaia Data Release 3 (DR3) that lie within the range covered by LAMOST cool dwarf spectroscopic parameters: 3200 K < T eff < 4300 K, ‑0.8 < [M/H] < 0.2 dex, and 4.5 < log g < 5.5 dex. Our values are derived based on machine-learning models trained with multiband photometry corrected for dust. The photometric data comprise optical data from the Sloan Digital Sky Survey r, i, and z bands, near-infrared data from the Two Micron All Sky Survey J, H, and K bands, and mid-infrared data from the ALLWISE W1 and W2 bands. We used both random forest and light gradient boosting machine machine-learning models and found similar results from both, with an error dispersion of 68 K, 0.22 dex, and 0.05 dex for T eff, [M/H], and log g, respectively. Assessment of the relative feature importance of different photometric colors indicated W1 ‑ W2 as most sensitive to both T eff and log g, with J ‑ H being most sensitive to [M/H]. We find that our values show a good agreement with the Apache Point Observatory Galactic Evolution Experiment, but are significantly different to those provided as part of Gaia DR3.

Keywords: late-type dwarf stars; m dwarf stars
Spectroscopic Detection of Alfvénic Waves in the Chromospheric Fibrils of a Solar-quiet Region

We report the detection of transverse magnetohydrodynamic waves, also known as Alfvénic waves, in the chromospheric fibrils of a solar-quiet region. Unlike previous studies that measured transversal displacements of fibrils in imaging data, we investigate the line-of-sight (LOS) velocity oscillations of the fibrils in spectral data. The observations were carried out with the Fast Imaging Solar Spectrograph of the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory. By applying spectral inversion to the Hα and Ca II 8542 Å line profiles, we determine various physical parameters, including the LOS velocity in the chromosphere of the quiet Sun. In the Hα data, we select two adjacent points along the fibrils and analyze the LOS velocities at those points. For the time series of the velocities that show high cross-correlation between the two points and do not exhibit any correlation with intensity, we interpret them as propagating Alfvénic wave packets. We identify a total of 385 Alfvénic wave packets in the quiet-Sun fibrils. The mean values of the period, velocity amplitude, and propagation speed are 7.5 minutes, 1.33 km s-1, and 123 km s-1, respectively. We find that the detected waves are classified into three groups based on their periods, namely, 3, 5, and 10 minute bands. Each group of waves exhibits distinct wave properties, indicating a possible connection to their generation mechanism. Based on our results, we expect that the identification of Alfvénic waves in various regions will provide clues to their origin and the underlying physical processes in the solar atmosphere.

Keywords: solar chromosphere; solar atmosphere; magnetohydrodynamics; alfven waves; quiet sun
Dependence of Chemical Abundance on the Cosmic-Ray Ionization Rate in IC 348

Ions (e.g., ${{\rm{H}}}_{3}^{+}$ , H2O+) have been used extensively to quantify the cosmic-ray ionization rate (CRIR) in diffuse sightlines. However, measurements of the CRIR in low-to-intermediate density gas environments are rare, especially when background stars are absent. In this work, we combine molecular line observations of CO, OH, CH, and HCO+ in the star-forming cloud IC 348, and chemical models to constrain the value of the CRIR and study the response of the distribution of chemical abundances. The cloud boundary is found to have an A V of approximately 4 mag. From the interior to the exterior of the cloud, the observed 13CO line intensities drop by an order of magnitude. The calculated average abundance of 12CO (assuming 12C/13C=65) is (1.2 ± 0.9) × 10-4, which decreases by a factor of 6 from the interior to the outside regions. The average abundance of CH (3.3 ± 0.7 × 10-8) is in good agreement with previous findings in diffuse and translucent clouds (A V < 5 mag). However, we did not find a decline in CH abundance in regions of high extinction (A V ≃ 8 mag) as previously reported in Taurus. By comparing the observed molecular abundances and chemical models, we find a decreasing trend of the CRIR as A V increases. The inferred CRIR of ζ cr = (4.7 ± 1.5) × 10-16 s-1 at low A V is consistent with ${{\rm{H}}}_{3}^{+}$ measurements toward two nearby massive stars.

Keywords: interstellar medium; interstellar molecules; chemical abundances; molecular clouds
Remarkable Migration of the Solar System from the Innermost Galactic Disk; a Wander, a Wobble, and a Climate Catastrophe on the Earth

Recent knowledge of Galactic dynamics suggests that stars radially move on the disk when they encounter transient spiral arms that are naturally generated during the process of disk formation. We argue that the large movement of the solar system from the innermost disk over its lifetime is inferred from an elemental abundance pattern of the Sun to those of solar twins within the Galactic chemical evolutionary framework. The implied metal-rich environment at the Sun's birthplace and its formation time are supported by measured silicon isotopic ratios in presolar silicon carbide grains. We perform numerical simulations of the dynamical evolution of disk stars in a Milky Way-like galaxy to identify the lifetime trajectory of the solar system. We find that a solar system born in the proximity of the Galactic bulge could travel to the current locus by the effect of radial migration induced by several major encounters with spiral arms. The frequent feature we identify is the repeated passages of stars inside the same spiral arm owing to the wobble of stars traveling in and out of the spiral arms. We predict that such episodes are evidenced in the Earth's geological history as snowball Earth and that their occurrence times are within our predictions. In particular, the stellar motion that vertically oscillates during passages through spiral arms occasionally leads to a split into two discrete passage episodes with an interval of several tens of megayears, implying two relevant snowball Earth events that occurred in rapid succession (∼720 and 650 million years ago).

Keywords: earth atmosphere; galaxy chemical evolution; galaxy dynamics; milky way disk; spiral arms; stellar abundances; stellar motion; solar abundances
Constraining High-redshift Stellar-mass Primordial Black Holes with Next-generation Ground-based Gravitational-wave Detectors

The possible existence of primordial black holes in the stellar-mass window has received considerable attention because their mergers may contribute to current and future gravitational-wave detections. Primordial black hole mergers, together with mergers of black holes originating from Population III stars, are expected to dominate at high redshifts (z ≳ 10). However, the primordial black hole merger rate density is expected to rise monotonically with redshift, while Population III mergers can only occur after the birth of the first stars. Next-generation gravitational-wave detectors such as the Cosmic Explorer (CE) and Einstein Telescope (ET) can access this distinctive feature in the merger rates as functions of redshift, allowing for direct measurement of the abundance of the two populations and hence for robust constraints on the abundance of primordial black holes. We simulate four months' worth of data observed by a CE-ET detector network and perform hierarchical Bayesian analysis to recover the merger rate densities. We find that if the universe has no primordial black holes with masses of ${ \mathcal O }(10{M}_{\odot })$ , the projected upper limit on their abundance f PBH as a fraction of dark matter energy density may be as low as ${f}_{\mathrm{PBH}}\sim { \mathcal O }({10}^{-5})$ , about two orders of magnitude lower than the current upper limits in this mass range. If instead f PBH ≳ 10-4, future gravitational-wave observations would exclude f PBH = 0 at the 95% credible interval.

Keywords: primordial black holes; gravitational waves; gravitational wave sources; gravitational wave astronomy
Dynamical Friction in Globular Cluster-rich Ultra-diffuse Galaxies: The Case of NGC5846-UDG1

Ultra-diffuse galaxies that contain a large sample of globular clusters (GCs) offer an opportunity to test the predictions of galactic dynamics theory. NGC5846-UDG1 is an excellent example, with a high-quality sample of dozens of GC candidates. We show that the observed distribution of GCs in NGC5846-UDG1 is suggestive of mass segregation induced by gravitational dynamical friction. We present simple analytic calculations, backed by a series of numerical simulations, that naturally explain the observed present-day pattern of GC masses and radial positions. Subject to some assumptions on the GC population at birth, the analysis supports the possibility that NGC5846-UDG1 resides in a massive dark matter halo. This is an example for the use of GC-rich systems as dynamical (in addition to kinematical) tracers of dark matter.

Keywords: low surface brightness galaxies; dynamical friction; globular star clusters; galaxy dynamics; hst photometry; dwarf galaxies; galaxy formation
An ALMA Molecular Inventory of Warm Herbig Ae Disks. I. Molecular Rings, Asymmetries, and Complexity in the HD 100546 Disk

Observations of disks with the Atacama Large Millimeter/submillimeter Array (ALMA) allow us to map the chemical makeup of nearby protoplanetary disks with unprecedented spatial resolution and sensitivity. The typical outer Class II disk observed with ALMA is one with an elevated C/O ratio and a lack of oxygen-bearing complex organic molecules, but there are now some interesting exceptions: three transition disks around Herbig Ae stars all show oxygen-rich gas traced via the unique detections of the molecules SO and CH3OH. We present the first results of an ALMA line survey at ≈337–357 GHz of such disks and focus this paper on the first Herbig Ae disk to exhibit this chemical signature—HD 100546. In these data, we detect 19 different molecules including NO, SO2, and CH3OCHO (methyl formate). We also make the first tentative detections of ${{\rm{H}}}_{2}^{13}\mathrm{CO}$ and 34SO in protoplanetary disks. Multiple molecular species are detected in rings, which are, surprisingly, all peaking just beyond the underlying millimeter continuum ring at ≈200 au. This result demonstrates a clear connection between the large dust distribution and the chemistry in this flat disk. We discuss the physical and/or chemical origin of these substructures in relation to ongoing planet formation in the HD 100546 disk. We also investigate how similar and/or different this molecular makeup of this disk is to other chemically well-characterized Herbig Ae disks. The line-rich data we present motivate the need for more ALMA line surveys to probe the observable chemistry in Herbig Ae systems, which offer unique insight into the composition of disks ices, including complex organic molecules.

Keywords: protoplanetary disks; astrochemistry; chemical abundances; interferometry; complex organic molecules; planet formation
Application of Convolutional Neural Networks to Predict Magnetic Fields' Directions in Turbulent Clouds

We adopt the deep learning method CASI-3D (convolutional approach to structure identification-3D) to infer the orientation of magnetic fields in sub-/trans-Alfvénic turbulent clouds from molecular line emission. We carry out magnetohydrodynamic simulations with different magnetic field strengths and use these to generate synthetic observations. We apply the 3D radiation transfer code RADMC-3D to model 12CO and 13CO (J = 1-0) line emission from the simulated clouds and then train a CASI-3D model on these line emission data cubes to predict magnetic field morphology at the pixel level. The trained CASI-3D model is able to infer magnetic field directions with a low error (≲10° for sub-Alfvénic samples and ≲30° for trans-Alfvénic samples). We further test the performance of CASI-3D on a real sub-/trans- Alfvénic region in Taurus. The CASI-3D prediction is consistent with the magnetic field direction inferred from Planck dust polarization measurements. We use our developed methods to produce a new magnetic field map of Taurus that has a three times higher angular resolution than the Planck map.

Keywords: interstellar medium; interstellar magnetic fields; convolutional neural networks; molecular clouds; magnetohydrodynamics
Chemical Compositions Of Red Giant Stars in the Old Open Cluster NGC 7789

We have gathered optical-region spectra, derived model atmosphere parameters, and computed elemental abundances for 15 red giant stars in the open cluster NGC 7789. We focus on the light element group CNOLi that provides clues to evolutionary changes associated with internal fusion events and chemical mixing. We confirm and extend an early report that NGC 7789 stars 193 and 301 have anomalously large Li abundances, and that these values are apparently unconnected to any other elements' abundances in these stars. A companion study of He I λ10830 lines in both field stars and cluster members shows that star 301 has a strong He feature while star 193 does not. Possible explanations for the large Li abundances of these stars include helium flash-induced mixing events and binary interactions at some past or present times. In either case an internal eruption of energy could cause fresh synthesis of lithium via the Cameron-Fowler Berillyum transport mechanism. Rapid transport of lithium to the outer layers may have created significant chromospheric transient disturbances, producing enough helium ionization to allow for the strong λ10830 absorption in star 301.

Keywords: high resolution spectroscopy; stellar atmospheres; chemically peculiar giant stars; open star clusters
NOEMA Redshift Measurements of Extremely Bright Submillimeter Galaxies near the GOODS-N

We report spectroscopic redshift measurements for three bright submillimeter galaxies (SMGs) near the GOODS-N field, each with SCUBA-2 850 μm fluxes >10 mJy, using the Northern Extended Millimeter Array (NOEMA). Our molecular line-scan observations of these sources, which occupy an ~7 arcmin2 area outside of the Hubble Space Telescope coverage of the field, reveal that two lie at z ~ 3.14. In the remaining object, we detect line emission consistent with CO(7-6), [C I], and H2O at z = 4.42. The far-infrared spectral energy distributions of these galaxies, constrained by SCUBA-2, NOEMA, and Herschel/SPIRE, indicate instantaneous star formation rates ~4000 M⊙ yr-1 in the z = 4.42 galaxy and ~2500 M⊙ yr-1 in the two z ~ 3.14 galaxies. Based on the sources' CO line luminosities, we estimate Mgas ~ 1011M⊙ and find gas depletion timescales of τdepl ~ 50 Myr, consistent with findings in other high-redshift SMGs. Finally, we show that the two z ~ 3.14 sources, which alone occupy a volume ~10 Mpc3, very likely mark the location of a protocluster of bright SMGs and less-dusty optical sources.

Keywords: submillimeter astronomy; high-redshift galaxy clusters; co line emission; galaxy evolution
A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). III. Discovery of a z = 4.72 Radio Galaxy with the Lyman Break Technique

We report a discovery of a z = 4.72 radio galaxy, HSC J083913.17+011308.1, using the Lyman break technique with the Hyper Suprime-Cam Subaru Strategic Survey (HSC-SSP) catalog for Very Large Array Faint Images of the Radio Sky at Twenty centimeter radio sources. The number of known high-z radio galaxies (HzRGs) at z > 3 is quite small to constrain the evolution of HzRGs so far. The deep and wide-area optical survey by HSC-SSP enables us to apply the Lyman break technique to a large search for HzRGs. For an HzRG candidate among pre-selected r-band dropouts with a radio detection, a follow-up optical spectroscopy with the Gemini Multi-Object Spectrographs (GMOS)/Gemini has been performed. The obtained spectrum presents a clear Lyα emission line redshifted to z = 4.72. The spectral energy distribution fitting analysis with the rest-frame UV and optical photometries suggests the massive nature of this HzRG with $\mathrm{log}{M}_{* }/{M}_{\odot }=11.4$ . The small equivalent width of Lyα and the moderately red UV colors indicate its dusty host galaxy, implying a chemically evolved and dusty system. The radio spectral index does not meet a criterion for an ultra-steep spectrum, ${\alpha }_{1400}^{325}$ of -1.1 and ${\alpha }_{1400}^{150}$ of -0.9, demonstrating that the HSC-SSP survey compensates for a subpopulation of HzRGs that are missed in surveys focusing on an ultra-steep spectral index.

Keywords: radio galaxies; active galaxies; high-redshift galaxies; lyman-break galaxies; spectroscopy
A Report on Stellar Companion Mass Estimates within Our Solar Neighborhood

We present mass estimates and companion demographics on stellar multiples within 25 pc, using a survey of stars of all spectral types done by Robo-AO and supplemented by Gaia. The survey combined direct imaging by Robo-AO, a robotic adaptive optics instrument for 2 m class telescopes, to detect tight companions (<4″ separation) and with Gaia astrometry to detect wider co-moving companions. We estimated the masses for 267 companions using empirical relations and, for a subset of 97, dynamical mass estimates. We utilized previous mass–magnitude models using contrasts measured from Gaia and Robo-AO to estimate the mass and also used the orvara python package, a Markov Chain Monte Carlo orbit fitter using the companion astrometry and Hipparcos-Gaia proper motion accelerations, to estimate dynamical masses. We compare agreements and discrepancies in mass estimates from these two methods.

Keywords: binary stars; close binary stars; companion stars; direct imaging; center of mass; stellar masses; adaptive optics; keplerian orbit
Electromagnetic Emission Driven by Electron Beam Instability in the Jovian Polar Regions

Upward energetic electron beams are often observed simultaneously with the plasma-wave emission in the Jovian polar regions, where the electron cyclotron frequency Ωce is much larger than the plasma frequency ωpe. This study gives a comprehensive wave and instability analysis in the extreme plasma environment with Ωce ≫ ωpe. We find that energetic electron beams can effectively drive the electron acoustic/magnetoacoustic instability. The excited electron acoustic/magnetoacoustic waves distribute from the parallel direction to the highly oblique direction, and their wave frequencies are always below the plasma frequency. These waves are electrostatic at parallel propagation, and exhibit electromagnetic polarization at oblique propagation. These theoretical predictions are qualitatively consistent with the main observed features of electromagnetic fluctuations in the Jovian polar regions. Therefore, we propose that upward electron beam-driven electron acoustic/magnetoacoustic waves can contribute to the plasma-wave emission in Jupiter's polar environments. Furthermore, energetic electron beam-driven electron acoustic/magnetoacoustic waves may exist in Saturn's polar regions and solar flare loops, where the extreme plasma condition Ωce ≫ ωpe is satisfied in these plasma environments.

Keywords: plasma physics; space plasmas; solar wind; planetary magnetospheres
Revealing the Nature of a Lyα Halo in a Strongly Lensed Interacting System at z = 2.92

Spatially extended halos of H I Lyα emission are now ubiquitously found around high-redshift star-forming galaxies. But our understanding of the nature and powering mechanisms of these halos is still hampered by the complex radiative transfer effects of the Lyα line and limited angular resolution. In this paper, we present resolved Multi Unit Spectroscopic Explorer (MUSE) observations of SGAS J122651.3+215220, a strongly lensed pair of L* galaxies at z = 2.92 embedded in a Lyα halo of L Lyα = (6.2 ± 1.3) × 1042 erg s-1. Globally, the system shows a line profile that is markedly asymmetric and redshifted, but its width and peak shift vary significantly across the halo. By fitting the spatially binned Lyα spectra with a collection of radiative transfer galactic wind models, we infer a mean outflow expansion velocity of ≈211 km s-1, with higher values preferentially found on both sides of the system's major axis. The velocity of the outflow is validated with the blueshift of low-ionization metal absorption lines in the spectra of the central galaxies. We also identify a faint (M 1500 ≈ -16.7) companion detected in both Lyα and the continuum, whose properties are in agreement with a predicted population of satellite galaxies that contribute to the extended Lyα emission. Finally, we briefly discuss the impact of the interaction between the central galaxies on the properties of the halo and the possibility of in situ fluorescent Lyα production.

Keywords: lyman-break galaxies; circumgalactic medium; extragalactic astronomy; galaxy interactions; cold neutral medium; galaxy winds
Near-infrared Opacity of Late M Dwarfs and Hot Jupiters: The E3Π-X3Δ Transition of TiO

The TiO E3Π-X3Δ transition is an important opacity source in the near-infrared spectra of late M dwarfs. The 0-0 band of the 48Ti16O E3Π-X3Δ electronic transition has been reanalyzed using a recently published set of high-resolution, high temperature absorption cross sections. The analysis has been extended to higher J values and an improved set of spectroscopic constants were determined. Calculated high-precision line lists for the 0-0 and 0-1 bands are provided with line strengths based on a previously measured experimental lifetime.

Keywords: laboratory astrophysics; spectral line lists
Bayesian Methods for Joint Exoplanet Transit Detection and Systematic Noise Characterization

The treatment of systematic noise is a significant aspect of transit exoplanet data processing due to the signal strength of systematic noise relative to a transit signal. Typically, the standard approach to transit detection is to estimate and remove systematic noise independently of and prior to a transit detection test. If a transit signal is present in a light curve, the process of systematic noise removal may distort the transit signal by overfitting and thereby reduce detection efficiency. We present a Bayesian framework for joint detection of transit signals and systematic noise characterization and describe the implementation of these detectors as optimal Neyman-Pearson likelihood ratio tests. The joint detectors reduce to closed form as matched filters under the assumption of a Gaussian Bayesian prior for the systematic noise. The performance of the exploratory detectors was evaluated in injection tests and show ∼2% improvement in overall detection efficiency relative to the standard approach. We find that joint detection efficiency is specifically improved for short-period, low transit-depth exoplanet transits, providing evidence in support of the hypothesis that joint detection may indeed help to mitigate overfitting. In addition, an initial feasibility test to detect known exoplanets in Kepler data using the joint detectors produced encouraging preliminary results.

Keywords: exoplanets; exoplanet detection methods; transit photometry; bayesian statistics; astronomy data analysis; red noise; time series analysis