adsabs/SciX_UAT_keywords huggingface dataset:
CEERS Key Paper. IV. A Triality in the Nature of HST-dark Galaxies

The new capabilities that JWST offers in the near- and mid-infrared (IR) are used to investigate in unprecedented detail the nature of optical/near-IR-faint, mid-IR-bright sources, with HST-dark galaxies among them. We gather JWST data from the CEERS survey in the Extended Groth Strip, jointly with HST data, and analyze spatially resolved optical-to-mid-IR spectral energy distributions to estimate photometric redshifts in two dimensions and stellar population properties on a pixel-by-pixel basis for red galaxies detected by NIRCam. We select 138 galaxies with F150W - F356W > 1.5 mag and F356W < 27.5 mag. The nature of these sources is threefold: (1) 71% are dusty star-forming galaxies (SFGs) at 2 < z < 6 with $9\lt \mathrm{log}{M}_{\star }/{M}_{\odot }\lt 11$ and a variety of specific SFRs (<1 to >100 Gyr-1); (2) 18% are quiescent/dormant (i.e., subject to reignition/rejuvenation) galaxies (QGs) at 3 < z < 5, with $\mathrm{log}{M}_{\star }/{M}_{\odot }\sim 10$ and poststarburst mass-weighted ages (0.5-1.0 Gyr); and (3) 11% are strong young starbursts with indications of high equivalent width emission lines (typically, [O III]+Hβ) at 6 < z < 7 (XELG-z6) and $\mathrm{log}{M}_{\star }/{M}_{\odot }\sim 9.5$ . The sample is dominated by disk-like galaxies with remarkable compactness for XELG-z6 (effective radii smaller than 0.4 kpc). Large attenuations in SFGs, 2 < A(V) < 5 mag, are found within 1.5 times the effective radius, approximately 2 kpc, while QGs present A(V) ~ 0.2 mag. Our SED-fitting technique reproduces the expected dust emission luminosities of IR-bright and submillimeter galaxies. This study implies high levels of star formation activity between z ~ 20 and z ~ 10, where virtually 100% of our galaxies had already formed 108 M ⊙, 60% had assembled 109 M ⊙, and 10% up to 1010 M ⊙ (in situ or ex situ).

Keywords: galaxy formation; galaxy evolution; high-redshift galaxies; stellar populations; broad band photometry; galaxy ages; james webb space telescope; galaxy quenching; galaxy processes; quenched galaxies; starburst galaxies; galaxy photometry
CHIPS: Complete History of Interaction-powered Supernovae

We present the public release of the Complete History of Interaction-Powered Supernovae (CHIPS) code, which is suited to model a variety of transients that arise from interaction with a dense circumstellar medium (CSM). Contrary to existing modelings, which mostly attach the CSM by hand, CHIPS self-consistently simulates both the creation of the CSM from mass eruption of massive stars prior to core collapse, and the subsequent supernova light curve. We demonstrate the performance of CHIPS by presenting examples of the density profiles of the CSM and the light curves. We show that the gross light-curve properties of putative interaction-powered transients (e.g., Type IIn supernovae, rapidly evolving transients and recently discovered fast blue optical transients) can be comprehensively explained with the output of CHIPS.

Keywords: supernovae; circumstellar matter; stellar mass loss; radiative transfer; computational methods
Red Asymmetry of H α Line Profiles during the Flares on the Active RS CVn-type Star II Pegasi

Stellar coronal mass ejections (CMEs) have recently attracted much attention for their impacts on stellar evolution and surrounding exoplanets. RS CVn-type stars could produce large flares, and therefore may have frequent CMEs. Here we report the capture of a possible CME or chromospheric condensation on the RS CVn-type star II Pegasi (II Peg) using high-resolution spectroscopic observation. Two flares were detected during the observation, and the low limits of the flare energies are of the order of 1033 erg and 1034 erg, respectively. Using mean spectrum subtraction, the H α residual shows red asymmetry during the flares, and the redshifted broad emission components are probably caused by chromospheric condensation or coronal rain. Moreover, a far redshifted extra emission component with a high bulk velocity of 429 km s‑1 was observed during the second flare and is probably due to a prominence eruption. The velocity greatly exceeds the star's escape velocity, which means that this eruption can develop into a CME. The CME mass is estimated to be 0.83–1.48 × 1020 g, which is slightly larger than the value expected from solar flare-CME extrapolation. The kinetic energy of CME, derived to be 0.76–1.15 × 1035 erg, is less than the kinetic energy extrapolated from solar events. Additionally, we could not completely rule out the possibility of chromospheric condensation resulting in the far redshifted extra emission. Finally, there is a blueshifted broad component in the subtracted H α profile derived using synthesized spectral subtraction when no flare happened, and its behavior is associated with the H α activity features.

Keywords: stellar activity; optical flares; stellar coronal mass ejections; spectroscopy
Host Galaxy Mass Combined with Local Stellar Age Improve Type Ia Supernovae Distances

Type Ia supernovae (SNe Ia) are standardizable candles, but for over a decade there has been a debate on how to properly account for their correlations with host galaxy properties. Using the Bayesian hierarchical model UNITY, we simultaneously fit for the SN Ia light curve and host galaxy standardization parameters on a set of 103 Sloan Digital Sky Survey II SNe Ia. We investigate the influences of host stellar mass, along with both localized (r <3 kpc) and host-integrated average stellar ages, derived from stellar population synthesis modeling. We find that the standardization for the light-curve shape (α) is correlated with host galaxy standardization terms (γi) requiring simultaneous fitting. In addition, we find that these correlations themselves are dependent on host galaxy stellar mass that includes a shift in the color term (β) of 0.8 mag, only significant at 1.2σ due to the small sample. We find a linear host mass standardization term at the 3.7σ level, that by itself does not significantly improve the precision of an individual SN Ia distance. However, a standardization that uses both stellar mass and average local stellar age is found to be significant at >3σ in the two-dimensional posterior space. In addition, the unexplained scatter of SNe Ia absolute magnitude post standardization, is reduced from ${0.122}_{-0.018}^{+0.019}$ to 0.109 ± 0.017 mag, or ∼10%. We do not see similar improvements when using global ages. This combination is consistent with either metallicity or line-of-sight dust affecting the observed luminosity of SNe Ia.

Keywords: type ia supernovae; observational cosmology; distance indicators; cosmological parameters
TOI-1728b: The Habitable-zone Planet Finder Confirms a Warm Super-Neptune Orbiting an M-dwarf Host

We confirm the planetary nature of TOI-1728b using a combination of ground-based photometry, near-infrared Doppler velocimetry and spectroscopy with the Habitable-zone Planet Finder. TOI-1728 is an old, inactive M0 star with Teff = ${3980}_{-32}^{+31}$ K, which hosts a transiting super-Neptune at an orbital period of ∼3.49 days. Joint fitting of the radial velocities and TESS and ground-based transits yields a planetary radius of ${5.05}_{-0.17}^{+0.16}$ R⊕, mass ${26.78}_{-5.13}^{+5.43}$ M⊕, and eccentricity ${0.057}_{-0.039}^{+0.054}$ . We estimate the stellar properties, and perform a search for He 10830 Šabsorption during the transit of this planet and claim a null detection with an upper limit of 1.1% with 90% confidence. A deeper level of He 10830 Šabsorption has been detected in the planet atmosphere of GJ 3470b, a comparable gaseous planet. TOI-1728b is the largest super-Neptune—the intermediate subclass of planets between Neptune and the more massive gas-giant planets—discovered around an M dwarf. With its relatively large mass and radius, TOI-1728 represents a valuable data point in the M-dwarf exoplanet mass-radius diagram, bridging the gap between the lighter Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs. With a low bulk density of ${1.14}_{-0.24}^{+0.26}$ g cm-3, and orbiting a bright host star (J ∼ 9.6, V ∼ 12.4), TOI-1728b is also a promising candidate for transmission spectroscopy both from the ground and from space, which can be used to constrain planet formation and evolutionary models.

Keywords: exoplanet detection methods; radial velocity; planet hosting stars
Inferring the Redshift of More than 150 GRBs with a Machine-learning Ensemble Model

Gamma-ray bursts (GRBs), due to their high luminosities, are detected up to a redshift of 10, and thus have the potential to be vital cosmological probes of early processes in the Universe. Fulfilling this potential requires a large sample of GRBs with known redshifts, but due to observational limitations, only 11% have known redshifts (z). There have been numerous attempts to estimate redshifts via correlation studies, most of which have led to inaccurate predictions. To overcome this, we estimated GRB redshift via an ensemble-supervised machine-learning (ML) model that uses X-ray afterglows of long-duration GRBs observed by the Neil Gehrels Swift Observatory. The estimated redshifts are strongly correlated (a Pearson coefficient of 0.93) and have an rms error, namely, the square root of the average squared error <Δz 2>, of 0.46 with the observed redshifts showing the reliability of this method. The addition of GRB afterglow parameters improves the predictions considerably by 63% compared to previous results in peer-reviewed literature. Finally, we use our ML model to infer the redshifts of 154 GRBs, which increase the known redshifts of long GRBs with plateaus by 94%, a significant milestone for enhancing GRB population studies that require large samples with redshift.

Keywords: gamma-ray bursts; redshift surveys; computational methods
Primordial Porous Structure of Chondrite Parent Bodies Due to Self-gravity

The porosity of an asteroid is important when studying the evolution of our solar system through small bodies and for planning mitigation strategies to avoid disasters due to asteroid impacts. Our knowledge of asteroid porosity largely relies on meteorites sampled on Earth. However, chondrites sampled on Earth are suggested to be sorted by strength. In this study, we obtained an estimate of the most porous structure of primordial "granular" chondrite parent bodies based on measurements of the compaction behavior of chondrite component analogs. We measured compaction curves of dust and dust-bead mixture samples. The dust sample consisted of various spherical and irregular particles with diameters on the order of 100-101 μm. The mixture sample consisted of dust and beads with different dust volume fractions (∼0.2-1). We used 1.5 and 4.8 μm particles as dust as a first step, although the typical size of materials in matrix may be much smaller. We approximated the compaction curve of each sample with a power-law form and calculated the porosity structure of the primordial chondrite parent bodies using the experimental results. Our results show that the primordial parent bodies are likely to have higher porosity than the chondrites. Moreover, the relatively higher volume fraction of the matrix may be one of the reasons why most meteorites with high porosity are carbonaceous chondrites.

Keywords: asteroids; planetesimals; planet formation; chondrites
Chemical Cartography with APOGEE: Mapping Disk Populations with a 2-process Model and Residual Abundances

We apply a novel statistical analysis to measurements of 16 elemental abundances in 34,410 Milky Way disk stars from the final data release (DR17) of APOGEE-2. Building on recent work, we fit median abundance ratio trends [X/Mg] versus [Mg/H] with a 2-process model, which decomposes abundance patterns into a "prompt" component tracing core-collapse supernovae and a "delayed" component tracing Type Ia supernovae. For each sample star, we fit the amplitudes of these two components, then compute the residuals Δ[X/H] from this two-parameter fit. The rms residuals range from ~0.01-0.03 dex for the most precisely measured APOGEE abundances to ~0.1 dex for Na, V, and Ce. The correlations of residuals reveal a complex underlying structure, including a correlated element group comprised of Ca, Na, Al, K, Cr, and Ce and a separate group comprised of Ni, V, Mn, and Co. Selecting stars poorly fit by the 2-process model reveals a rich variety of physical outliers and sometimes subtle measurement errors. Residual abundances allow for the comparison of populations controlled for differences in metallicity and [α/Fe]. Relative to the main disk (R = 3-13 kpc), we find nearly identical abundance patterns in the outer disk (R = 15-17 kpc), 0.05-0.2 dex depressions of multiple elements in LMC and Gaia Sausage/Enceladus stars, and wild deviations (0.4-1 dex) of multiple elements in ω Cen. The residual abundance analysis opens new opportunities for discovering chemically distinctive stars and stellar populations, for empirically constraining nucleosynthetic yields, and for testing chemical evolution models that include stochasticity in the production and redistribution of elements.

Keywords: milky way disk; galaxy chemical evolution; stellar populations
The Circumgalactic Hα Spectrograph (CHαS). I. Design, Engineering, and Early Commissioning

The Circumgalactic Hα Spectrograph (CHαS) is a ground-based optical integral field spectrograph designed to detect ultrafaint extended emission from diffuse ionized gas in the nearby universe. CHαS is particularly well suited for making direct detections of tenuous Hα emission from the circumgalactic medium (CGM) surrounding low-redshift galaxies. It efficiently maps large regions of the CGM in a single exposure, targeting nearby galaxies (d < 35 Mpc) where the CGM is expected to fill the field of view. We are commissioning CHαS as a facility instrument at MDM Observatory. CHαS is deployed in the focal plane of the Hiltner 2.4 m telescope, utilizing nearly all of the telescope's unvignetted focal plane (10'-15') to conduct wide-field spectroscopic imaging. The catadioptric design provides excellent wide-field imaging performance. CHαS is a pupil-imaging spectrograph employing a microlens array to divide the field of view into >60,000 spectra. CHαS achieves an angular resolution of [1.3-2.6] arcseconds and a resolving power of R = [10,000-20,000]. Accordingly, the spectrograph can resolve structure on the scale of 1-5 kpc (at 10 Mpc) and measure velocities down to 15-30 km s-1. CHαS intentionally operates over a narrow (30 Å) bandpass; however, it is configured to adjust the central wavelength and target a broad range of optical emission lines individually. A high-diffraction efficiency volume phase holographic grating ensures high throughput across configurations. CHαS maintains a high grasp and moderate spectral resolution, providing an ideal combination for mapping discrete, ultralow-surface brightness emission on the order of a few milli-Rayleigh.

Keywords: spectroscopy; circumgalactic medium; astronomical instrumentation
Supernovae Origin for the Low-latitude Intermediate-velocity Arch and the North Celestial Pole Loop

Supernova explosions attributed to the unseen companion in several binary systems identified by the Third Gaia Data Release (Gaia DR3) may be responsible for a number of well-known and well-studied features in the radio sky, including the low-latitude intermediate-velocity (LLIV) arch and the north celestial pole (NCP) loop. Slices from the longitude-latitude-velocity data cube of the λ-21 cm Galactic neutral hydrogen HI4PI survey show multiple signatures of an expanding shell. The source of this expansion, which includes the LLIV arch on the approaching side, may be the neutron star candidate in the Gaia DR3 1093757200530267520 binary. If we make the simplifying assumptions that the expansion of the cavity is uniform and spherically symmetric, then the explosion took place about 700,000 yr ago. The momentum is in reasonable agreement with recent model estimates for a supernova this old. The H I on the receding side of this cavity is interacting with the gas approaching us on the near side of a second cavity. The NCP loop appears to be located at the intersection of these two expanding features. The neutron star candidate in the Gaia DR3 1144019690966028928 binary may be (in part) responsible for this cavity. Explosions from other candidates may account for the observed elongation along the line of sight of this second cavity. We can use the primary star in these binaries to anchor the distances to the LLIV arch and NCP loop, which are ~167 and ~220 pc, respectively.

Keywords: interstellar medium
MagAO Observations of the Binary Microlens OGLE-2014-BLG-1050 Prefer the Higher-mass Solution

We report adaptive optics (AO) follow-up imaging of OGLE-2014-BLG-1050, which is the second binary microlensing event with space-based parallax measurements. The degeneracy in microlens parallax πE led to two sets of solutions, either a ∼ (0.9, 0.35)M⊙ binary at ∼3.5 kpc or a ∼(0.2, 0.07)M⊙ binary at ∼1.1 kpc. We measure the flux blended with the microlensed source by conducting Magellan AO observations, and find that the blending is consistent with the predicted lens flux from the higher-mass solution. From the combination of the AO flux measurement together with previous lensing constraints, it is estimated that the lens system consists of a ${1.05}_{-0.07}^{+0.08}\,{M}_{\odot }$ primary and a ${0.38}_{-0.06}^{+0.07}{M}_{\odot }$ secondary at ${3.43}_{-0.21}^{+0.19}$ kpc. * This paper includes data gathered with the 6.5m Magellan Clay Telescope at Las Campanas Observatory, Chile.

Keywords: binary lens microlensing; gravitational microlensing; high-resolution microlensing event imaging
The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity

We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF "NEID" precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday "lag" between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys. * HD 26965 is also known as 40 Eridani A, which is the host star of the planet Vulcan in the Star Trek universe.

Keywords: radial velocity
Accurate Gaunt Factors for Nonrelativistic Quadrupole Bremsstrahlung

The exact result for nonrelativistic quadrupole bremsstrahlung in a Coulomb field was established only recently in Pradler & Semmelrock. It requires the evaluation and integration of hypergeometric functions across a wide range of parameters and arguments, which, in practice, is unfeasible. Here we provide a highly accurate tabulation of the Gaunt factor for quadrupole radiation, its thermal average in a Maxwellian plasma, and the associated cooling function over the entire kinematically relevant range. In addition, we provide a simple approximate formula for the emission cross section that works to within a few percent accuracy for all practical purposes. The results can be applied to the scattering of electrons with themselves, for which quadrupole radiation is the dominant process.

Keywords: interstellar medium; interstellar thermal emission; interstellar emissions
Venus Observations at 40 and 90 GHz with CLASS

Using the Cosmology Large Angular Scale Surveyor, we measure the disk-averaged absolute Venus brightness temperature to be 432.3 ± 2.8 K and 355.6 ± 1.3 K in the Q and W frequency bands centered at 38.8 and 93.7 GHz, respectively. At both frequency bands, these are the most precise measurements to date. Furthermore, we observe no phase dependence of the measured temperature in either band. Our measurements are consistent with a CO2-dominant atmospheric model that includes trace amounts of additional absorbers like SO2 and H2SO4.

Keywords: venus; brightness temperature; atmospheric composition
Hycean Exoplanets as Targets for Technosignature Detection: A Case Study of K2-18 b in the 3-10 GHz Band

Recently the James Webb Space Telescope performed near-infrared spectroscopic observations of the atmosphere of a potential Hycean exoplanet, K2-18 b. These spectra provided evidence of methane and carbon dioxide in its atmosphere, along with a possible line attributed to biomarker dimethyl sulfide. In this work, we present triggered narrow-band radio observations of K2-18 b conducted using the Allen Telescope Array over 3-10 GHz, in search of signs of artificially produced radio emissions (technosignatures). We do not find any spatially isolated signals in the direction of K2-18 b, establishing lower and upper limits on the equivalent isotropic radiated power (~1013-1016 W) of potential extraterrestrial transmitters between 3 and 10 GHz. This study emphasizes the importance of ongoing observations to further explore K2-18 b's potential as a candidate for the detection of technosignatures.

Keywords: radio observatories; observational astronomy; exoplanet astronomy; radio interferometry; radio astronomy; exoplanets; astronomical methods; astronomical techniques; doppler shift; astrobiology
A Statistical Relation between Mass, Age, and Velocity Dispersion in the Solar Neighborhood

The stellar kinematics of the Galactic disk are the main factors constraining disk formation and evolution processes in the Milky Way. In this paper, we investigate a statistical relation between stellar mass, age, and velocity dispersion for stars in the solar neighborhood. Age-velocity dispersion relations, with their applications, have been studied in detail before, but their correlation with mass was mostly neglected. To investigate this relation, we use proper motion data of more than 113,035 stars in the Galactic disk (with solar distances less than 150 pc) provided by the third data release of the Gaia mission, and for stellar mass and age, Gaia's Final Luminosity Age Mass Estimator is implemented. We analyze this data and the correlations between the parameters with random forest regression, which is an ensemble statistical-learning technique. Finally, we show that, by considering stellar mass alongside age, we can determine velocity dispersions with an average relative error and a mean absolute error of about 9% and 2.68 km s-1, respectively. We also find that the correlation of stellar age with velocity dispersion is 3-8 times more than mass, which varies due to the different stellar types and masses. *Based on the third data release of the Gaia space telescope.

Keywords: astrostatistics techniques; stellar dynamics; solar neighborhood