adsabs/SciX_UAT_keywords huggingface dataset:
Stellar Populations of Lyα-emitting Galaxies in the HETDEX Survey. I. An Analysis of LAEs in the GOODS-N Field

We present the results of a stellar population analysis of 72 Lyα-emitting galaxies (LAEs) in GOODS-N at 1.9 < z < 3.5 spectroscopically identified by the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We provide a method for connecting emission-line detections from the blind spectroscopic survey to imaging counterparts, a crucial tool needed as HETDEX builds a massive database of ~1 million Lyα detections. Using photometric data spanning as many as 11 filters covering 0.4 < λ (μm) < 4.5 from the Hubble Space Telescope and Spitzer Space Telescope, we study the objects' global properties and explore which properties impact the strength of Lyα emission. We measure a median stellar mass of ${0.8}_{-0.5}^{+2.9}\times {10}^{9}\ {M}_{\odot }$ and conclude that the physical properties of HETDEX spectroscopically selected LAEs are comparable to LAEs selected by previous deep narrowband studies. We find that stellar mass and star formation rate correlate strongly with the Lyα equivalent width. We then use a known sample of z > 7 LAEs to perform a protostudy of predicting Lyα emission from galaxies in the epoch of reionization, finding agreement at the 1σ level between prediction and observation for the majority of strong emitters.

Keywords: galaxy evolution; galaxy formation; lyman-alpha galaxies; high-redshift galaxies
Laboratory Measurements of Stretching Band Strengths of Deuterated Quenched Carbonaceous Composites

The observed large variation in the abundance of deuterium (D) in the interstellar medium suggests that a significant fraction of D may be depleted into polycyclic aromatic hydrocarbons (PAHs). Signatures of the deuteration of PAHs are expected to appear most clearly through the C-D stretching modes at 4.4-4.7 μm, whose strengths in emission spectra relative to those of the C-H stretching modes at 3.3-3.5 μm provide the relative abundance of D to hydrogen (H) in PAHs, once we have accurate relative band strengths of both stretching modes. We report experimental results of the band strengths of the C-D stretching modes relative to the C-H stretching modes. We employ a laboratory analog of interstellar carbonaceous dust, Quenched Carbonaceous Composite (QCC), and synthesize deuterated QCC (D-QCC) by replacing the QCC starting gas of CH4 with mixtures of CH4 and CD4 with various ratios. Infrared spectra of D-QCC are taken to estimate the relative band strengths of the stretching modes, while the D/H ratios in the D-QCC samples are measured with a nanoscale secondary ion mass spectrometer. We obtain relative strengths of aromatic and aliphatic C-D to C-H stretches as 0.56 ± 0.04 and 0.38 ± 0.01 per D/H, respectively. The ratio for the aromatic stretches is in good agreement with the results of theoretical calculations, while that for the aliphatic stretches is smaller than that for the aromatic stretches. The present results do not significantly change the D/H ratios in interstellar PAHs that have previously been estimated from observed spectra.

Keywords: interstellar medium; interstellar dust; polycyclic aromatic hydrocarbons; isotopic abundances; infrared astronomy
A Dark Siren Measurement of the Hubble Constant with the LIGO/Virgo Gravitational Wave Event GW190412 and DESI Galaxies

We present a measurement of the Hubble Constant H 0 using the gravitational wave event GW190412, an asymmetric binary black hole merger detected by LIGO/Virgo, as a dark standard siren. This event does not have an electromagnetic counterpart, so we use the statistical standard siren method and marginalize over potential host galaxies from the Dark Energy Spectroscopic Instrument (DESI) survey. GW190412 is well-localized to 12 deg2 (90% credible interval), so it is promising for a dark siren analysis. The dark siren value for ${H}_{0}={85.4}_{-33.9}^{+29.1}$ km s-1 Mpc-1, with a posterior shape that is consistent with redshift overdensities. When combined with the bright standard siren measurement from GW170817 we recover ${H}_{0}={77.96}_{-5.03}^{+23.0}$ km s-1 Mpc-1, consistent with both early and late-time Universe measurements of H 0. This work represents the first standard siren analysis performed with DESI data, and includes the most complete spectroscopic sample used in a dark siren analysis to date.

Keywords: gravitational waves; gravitational wave astronomy; cosmology; hubble constant; observational cosmology; cosmological parameters
Consequences for the Scalar Field Dark Matter Model from the McGaugh Observed-baryon Acceleration Correlation

Although the standard cosmological model, the so-called Λ cold dark matter (ΛCDM), appears to fit well observations at the cosmological level, it is well known that it possesses several inconsistencies at the galactic scales. In order to address the problems of the ΛCDM on a small scale, some alternative models have been proposed. Among the most popular candidates, the proposal that dark matter in the universe is made of ultralight bosons is a strong candidate today. For this work, we study through an analytical approach the consequences arising from comparing the Spitzer Photometry and Accurate Rotation Curves catalog observed-baryon acceleration correlation with the scalar field dark matter model. We carry out such analysis either considering the features of galactic halos extracted from structure-formation simulations or considering the existence of other non-dark-matter elements in the whole system (such as baryons or a supermassive black hole). Specifically, we address a recent claim that the model is not capable of reproducing a constant surface density in the core, in contrast to what observations suggest for a host of galaxies with different sizes and morphologies. In this direction, we show that this discrepancy can be alleviated once the contributions of non-dark-matter constituents in the whole galactic system are taken into account. Additionally, we find that a mass of m ≃ 1.41 × 10-22 eV/c2 is capable of reproducing all of our findings and correctly adjusting the rotation curves coming from the Milky Way galaxy.

Keywords: milky way dark matter halo
First Emulsion γ-Ray Telescope Imaging of the Vela Pulsar by the GRAINE 2018 Balloon-borne Experiment

We are developing the Gamma-Ray Astro-Imager with Nuclear Emulsion project, designed for 10 MeV-100 GeV cosmic γ-ray observations with a high angular resolution (5'/0.°08 at 1-2 GeV) and a polarization-sensitive large-aperture (~10 m2) emulsion telescope for repeated long-duration balloon flights. In 2018, a balloon-borne experiment was carried out in Australia with a 0.38 m2 sensitive area and a flight duration of 17.4 hr, including 6.7 hr of Vela observations. Significant improvements compared with the 2015 balloon-borne experiment were achieved by a factor of 5, including both an increase in effective area × time and a reduction in the background contribution. We aimed to demonstrate the telescope's overall performance based on detection and imaging of a known γ-ray source, the Vela pulsar. A robust detection of the Vela pulsar was achieved with a 68% containment radius of 0.°42, at a significance of 6σ, at energies above 80 MeV. The resulting angular profile is consistent with that of a pointlike source. We achieved the current best imaging performance of the Vela pulsar using an emulsion γ-ray telescope with the highest angular resolution of any γ-ray telescope to date.

Keywords: gamma-ray astronomy; cosmic rays; high altitude balloons
Transit Depth Variations Reveal TOI-216 b to be a Super-puff

The planets of the TOI-216 system have been previously observed to exhibit large transit-timing variations, which enabled precise mass characterization of both transiting planets. In the first year of TESS observations, TOI-216 b exhibited grazing transits, precluding a measurement of its radius. In new observations, we demonstrate the orbit of the planet has precessed and it is now fully transiting, so we can accurately measure its radius. TOI-216 b is a puffy Neptune-mass planet, with a much larger radius that is now well constrained to ${7.84}_{-0.19}^{+0.21}$ R ⊕ and a density of 0.201 ± 0.017 g cm-3. We numerically integrate the system across the TESS observations to update and refine the masses and orbits of both planets, finding the uncertainty in the masses are now dominated by uncertainties in the stellar parameters. TOI-216 b represents a growing class of super-puff planets in orbital resonances and with a companion in a nearly circular orbit, suggesting the early evolution of these planets is driven by smooth disk migration.

Keywords: exoplanets; transit photometry; transit timing variation method; transit duration variation method
Evaluating the Consistency of Cosmological Distances Using Supernova Siblings in the Near-infrared

The study of supernova (SN) siblings, supernovae with the same host galaxy, is an important avenue for understanding and measuring the properties of Type Ia SN Ia light curves (LCs). Thus far, sibling analyses have mainly focused on optical LC data. Considering that LCs in the near-infrared (NIR) are expected to be better standard candles than those in the optical, we carry out the first analysis compiling SN siblings with only NIR data. We perform an extensive literature search of all SN siblings and find six sets of siblings with published NIR photometry. We calibrate each set of siblings ensuring they are on homogeneous photometric systems, fit the LCs with the SALT3-NIR and SNooPy models, and find median absolute differences in μ values between siblings of 0.248 and 0.186 mag, respectively. To evaluate the significance of these differences beyond measurement noise, we run simulations that mimic these LCs and provide an estimate for uncertainty on these median absolute differences of ∼0.052 mag, and we find that, statistically, our analysis rules out the nonexistence of intrinsic scatter in the NIR at the 99% level. When comparing the same sets of SN siblings, we observe a median absolute difference in μ values between siblings of 0.177 mag when using optical data alone as compared to 0.186 mag when using NIR data alone. It is unclear if these results may be due to limited statistics or poor quality NIR data, all of which will be improved with the Nancy Grace Roman Space Telescope.

Keywords: supernovae; cosmology
Winds and Disk Turbulence Exert Equal Torques on Thick Magnetically Arrested Disks

The conventional accretion disk lore is that magnetized turbulence is the principal angular momentum transport process that drives accretion. However, when dynamically important large-scale magnetic fields thread an accretion disk, they can produce mass and angular momentum outflows, known as winds, that also drive accretion. Yet, the relative importance of turbulent and wind-driven angular momentum transport is still poorly understood. To probe this question, we analyze a long-duration (1.2 × 105 r g /c) simulation of a rapidly rotating (a = 0.9) black hole feeding from a thick (H/r ∼ 0.3), adiabatic, magnetically arrested disk (MAD), whose dynamically important magnetic field regulates mass inflow and drives both uncollimated and collimated outflows (i.e., winds and jets, respectively). By carefully disentangling the various angular momentum transport processes within the system, we demonstrate the novel result that disk winds and disk turbulence both extract roughly equal amounts of angular momentum from the disk. We find cumulative angular momentum and mass accretion outflow rates of $\dot{L}\propto {r}^{0.9}$ and $\dot{M}\propto {r}^{0.4}$ , respectively. This result suggests that understanding both turbulent and laminar stresses is key to understanding the evolution of systems where geometrically thick MADs can occur, such as the hard state of X-ray binaries, low-luminosity active galactic nuclei, some tidal disruption events, and possibly gamma-ray bursts.

Keywords: black holes; high energy astrophysics; accretion; relativistic jets; relativistic disks
Solar Eruptive Phenomena Associated with Solar Energetic Electron Spectral Types

The energy spectral shape of solar energetic electron events carries important information on the energetic electron source/acceleration at the Sun. We investigate the association of six newly identified solar energetic electron spectral types with solar eruptive phenomena, including the downward double-power-law (DDPL) spectrum with break energy E B above 20 keV (DDPL ), DDPL with E B below 20 keV (DDPL ), upward double-power law (UDPL), single-power-law (SPL), Ellision–Ramaty–like (ER), and logarithmic-parabola (LP). We find that the SPL type shows (the other five types show) an association with hard X-ray flares of ∼38% (∼55%–82%) and an association with west-limb coronal mass ejections (CMEs) of ∼76% (∼85%–93%). Among the other five types, the DDPL and ER (LP and DDPL ) types only have an association with type II radio bursts of ∼7%–8% (∼16%–20%) and an association with halo CMEs of ∼5%–9% (∼11%–21%); however, the UDPL type exhibits a significant (∼47% and ∼50%) association with type II bursts and halo CMEs, with a significantly faster median CME speed of km s‑1. For DDPL (DDPL ) with a positive (no) correlation between spectral indexes and no (a positive) correlation between the spectral index and break energy, the spectrum appears to be flatter as the associated CME (flare) becomes faster (stronger). These results suggest that the SPL type can result from the initial acceleration process that likely occurs high in the corona, and then provide seed populations for further acceleration processes to form the other five types: the DDPL and ER types via flare-related processes, the LP and DDPL types via CME-related processes, and the UDPL type via CME-driven shocks.

Keywords: solar energetic particles; solar particle emission; solar activity
Blueshifted Si IV 1402.77 Å Line Profiles in a Moving Flare Kernel Observed by IRIS

We analyze the spectra of a slipping flare kernel observed during the 2015 June 22 M6.5-class flare by the Interface Region Imaging Spectrograph (IRIS). During the impulsive and peak phases of the flare, loops exhibiting an apparent slipping motion along the ribbons were observed in the 131 Å channel of SDO/AIA. The IRIS spectrograph slit observed a portion of the ribbons, including a moving kernel corresponding to a flare loop footpoint in Si IV, C II, and Mg II at a very-high 1 s cadence. The spectra observed in the kernel were mostly redshifted and exhibited pronounced red wings, as typically observed in large flares. However, in a small region in one of the ribbons, the Si IV 1402.77 Å line was partially blueshifted, with the corresponding Doppler velocity ∣v D∣ exceeding 50 km s-1. In the same region, the C II 1334.53, 1335.66, and 1335.71 Å lines were weakly blueshifted (∣v D∣ < 20 km s-1) and showed pronounced blue wings, which were also observed in the Mg II k 2796.35 Å as well as the Mg II triplet 2798.75 and 2798.82 Å lines. Using high-cadence AIA observations we found that the region where the blueshifts occurred corresponds to the accelerating kernel front as it moved through a weak field region. The IRIS observations with high resolution allowed us to capture the acceleration of the kernel under the slit for the first time. The unique observations of blueshifted chromospheric and TR lines provide new constraints for current models of flares.

Keywords: solar transition region; solar ultraviolet emission; solar flares; solar chromosphere; solar magnetic reconnection
Planar Magnetic Structures Downstream of Coronal Mass Ejection-driven Shocks in the Inner Heliosphere

Planar magnetic structures (PMSs), characterized by interplanetary magnetic field vectors remaining parallel to a specific plane, are commonly observed in the solar wind, especially in the sheath region of interplanetary coronal mass ejections (ICMEs). In this study, PMS events in the 2 hr regions downstream of ICME-driven shocks were investigated to reveal the relationship between PMS formation and shock environment using data collected by the Parker Solar Probe, Solar Orbiter, and Venus Express spacecraft in the inner heliosphere. PMS events are identified in the majority (around 93%) of the postshock 2 hr regions, with transit times ranging from 10 to 120 minutes, which demonstrates their common occurrence associated with ICME-driven shocks. About 33% of the detected PMS events cover the whole 2 hr intervals, called full PMS events. Most of the full PMS events are observed in the downstream region of quasi-perpendicular shocks. In addition, statistical results show that full PMS events occurring in the downstream region of quasi-perpendicular shocks are generally associated with higher magnetic compression ratios, which implies that full PMS events are more likely to be formed in the downstream region of strong quasi-perpendicular shocks.

Keywords: interplanetary magnetic fields; interplanetary shocks; interplanetary physics; solar wind
A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster

We report metallicities for three ~Gyr-old stars in the Milky Way nuclear star cluster (NSC) using high-resolution near-infrared spectroscopy. We derive effective temperatures from a calibration with Sc line strength, which yields results in good agreement with other methods, and metallicities from spectral fits to Fe I lines. Our derived metallicities range from -1.2 < [Fe/H] < + 0.5, a span of 1.7 dex. In addition we use isochrone projection to obtain masses of 1.6-4.3 M ⊙, and ages assuming single-star evolution. The oldest of these stars is 1.5 Gyr while the youngest and most metal-rich is only 100 Myr. The wide range in metallicity poses interesting questions concerning the chemical evolution and enrichment of the NSC and adds to the evidence for the presence of a young, metal-rich population in the NSC. We suggest that the candidate intermediate-age, metal-poor ([Fe/H] = -1.2) star may be best explained as a blue straggler from an underlying old population.

Keywords: stellar abundances; galactic center; early-type stars
Penetrative Convection for Rotating Boussinesq Flow in Tilted f-planes

In this paper, we have performed linear instability analysis of the penetrative convection for the Boussinesq flow on a tilted f-plane. We have discussed the onset of instability as stationary and oscillatory convection. For the stationary convection, it has been shown that the penetration of convection is hindered by the stability of the upper, less unstable layer. For the oscillatory convection, however, the conclusion is different. We have computed the penetrative convection for both prograde and retrograde waves. The result indicates that for the prograde wave, under certain circumstances, the penetrative convection in the upper layer can be more vigorous than that in the lower unstable layer. For the retrograde wave, on the other hand, the stability in the upper layer always has a negative effect on the penetrative convection. Our calculation on the tilted f-plane has reproduced many features, such as teleconvection and multilayer roll convection, previously discovered on the penetrative convection in the spherical geometry. The dependence of penetrative distance on the Ekman number, the Prandtl number, and the stability parameter has been analyzed.

Keywords: stellar convective zones; stellar structures; stellar rotation
Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78

Highly r-process-enhanced (RPE) stars are rare and usually metal poor ([Fe/H] < ‑1.0), and they mainly populate the Milky Way halo and dwarf galaxies. This study presents the discovery of a relatively bright (V = 12.72), highly RPE (r-II) star ([Eu/Fe] = +1.32, [Ba/Eu] = ‑0.95), LAMOST J020623.21+494127.9. This star was selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium-resolution (R ∼ 7500) spectroscopic survey; follow-up high-resolution (R ∼ 25,000) observations were conducted with the High Optical Resolution Spectrograph installed on the Gran Telescopio Canarias. The stellar parameters (T eff = 4130 K, = 1.52, [Fe/H] = ‑0.54, ξ = 1.80 km s‑1) have been inferred taking into account nonlocal thermodynamic equilibrium effects. The abundances of [Ce/Fe], [Pr/Fe], and [Nd/Fe] are +0.19, +0.65, and +0.64, respectively, relatively low compared to the Solar r-process pattern normalized to Eu. This star has a high metallicity ([Fe/H] = ‑0.54) compared to most other highly RPE stars and has the highest measured abundance ratio of Eu to H ([Eu/H] = +0.78). It is classified as a thin-disk star based on its kinematics and does not appear to belong to any known stream or dwarf galaxy.

Keywords: stellar abundances; fundamental parameters of stars; chemically peculiar stars
Harmonic Radio Emission in Randomly Inhomogeneous Plasma

In the present paper, we describe a theoretical model of the generation of harmonic emissions of type III solar radio bursts. The goal of our study is to fully take into account the most efficient physical processes involved in the generation of harmonic electromagnetic emission via nonlinear coupling of Langmuir waves in randomly inhomogeneous plasma of solar wind ( $l+{l}^{{\prime} }\to t$ ). We revisit the conventional mechanism of coalescence of primarily generated and back-scattered Langmuir waves in quasihomogeneous plasma. Additionally, we propose and investigate another mechanism that generates harmonic emission only in a strongly inhomogeneous plasma: the nonlinear coupling of incident and reflected Langmuir waves inside localized regions with enhanced plasma density (clumps), in the close vicinity of the reflection point. Both mechanisms imply the presence of strong density fluctuations in plasma. We use the results of a probabilistic model of beam-plasma interaction and evaluate the efficiency of energy transfer from Langmuir waves to harmonic emission. We infer that harmonic emissions from a quasihomogeneous plasma are significantly more intense than found in previous studies. The efficiency of Langmuir wave conversion into electromagnetic harmonic emission is expected to be higher at large heliospheric distances for the mechanism operating in quasihomogeneous plasma and at small heliocentric distances for the one operating in inhomogeneous plasma. The evaluation of emission intensity in quasihomogeneous plasma may also be applied for type II solar radio bursts. The radiation pattern in both cases is quadrupolar, and we show that emission from density clumps may efficiently contribute to the visibility of harmonic radio emission.

Keywords: solar wind; interplanetary turbulence; solar coronal waves