adsabs/SciX_UAT_keywords huggingface dataset:
Direct Constraints on the Extremely Metal-poor Massive Stars Underlying Nebular C IV Emission from Ultra-deep HST/COS Ultraviolet Spectroscopy

Metal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low-metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six local (z < 0.02) galaxies that power strong nebular C IV emission approaching that encountered at z > 6. We find that the strength and spectral profile of the nebular C IV in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C IV escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe 2-4 times above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high redshift, but also suggests a unique path toward validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra.

Keywords: blue compact dwarf galaxies; massive stars; stellar populations; high-redshift galaxies; ultraviolet astronomy
The Mass Density of Mg II Absorbers from the Australian Dark Energy Survey

We present an all-southern sky survey for Mg II λλ2796, 2803 doublet absorbers in 951 z < 4 active galactic nucleus/quasar spectra from the Australian Dark Energy Survey. The spectral resolution ranges from R = 1400 to 1700 over the wavelengths 3700–8800 Å. The survey has a 5σ detection completeness of 50% and above for rest-frame equivalent widths W r (2796) ≥ 0.3 Å. We studied 656 Mg II absorption systems over the redshift range 0.33 ≤ z ≤ 2.19 with equivalent widths 0.3 ≤ W r (2796) ≤ 3.45 Å. The equivalent width distribution is well fit by an exponential function with W * = 0.76 ± 0.04 Å, and the redshift path density exhibits very little evolution. Overall, our findings are consistent with the large, predominantly northern sky, surveys of Mg II absorbers. We developed and implemented a Monte Carlo model informed by a high-resolution Mg II survey for determining the Mg II mass density, ΩMg II . We found ΩMg II ∼ 5 × 10‑7 with no evidence of evolution over a ∼7 Gyr time span following Cosmic Noon. Incorporating measurements covering 2.0 ≤ z ≤ 6.4 from the literature, we extended our insights into Mg II mass density evolution from the end of reionization well past the Cosmic Noon epoch. The presented Monte Carlo model has potential for advancing our knowledge of the evolution of mass densities of metal ions common to quasar absorption line studies, as it exploits the efficiency of large low-resolution surveys while requiring only small samples from expensive high-resolution surveys.

Keywords: quasar absorption line spectroscopy; circumgalactic medium; surveys; cosmological principle
The Relativistic Spin Precession in the Compact Double Neutron Star System PSR J1946+2052

We observe systematic profile changes in the visible pulsar of the compact double neutron star system PSR J1946+2052 using observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The interpulse of PSR J1946+2052 changed from a single-peak to a double-peak shape from 2018–2021. We attribute this evolution as the result of the relativistic spin precession of the pulsar. With the high sensitivity of FAST, we also measure significant polarization for the first time, allowing us to model this with the precessional rotating vector model. Assuming, to the first order, a circular hollow-cone-like emission beam pattern and taking the validity of general relativity (GR), we derive the binary's orbital inclination angle ( ${{63}^{\circ }}_{-{3}^{\circ }}^{+{5}^{\circ }}$ ) and pulsar's spin geometry. The pulsar's spin vector and the orbital angular momentum vector are found to be only slightly misaligned ( ${{0.}^{\circ }21}_{-{0.}^{\circ }10}^{+{0.}^{\circ }28}$ ). The quoted uncertainties do not reflect the systematic uncertainties introduced by our model assumptions. By simulating future observations of profile and polarization evolution, we estimate that we could constrain the precession rate within a 43% uncertainty in 9 yr. Hence, we suggest that the system's profile evolution could be combined with precise pulsar timing to test GR in the future.

Keywords: general relativity
A High-precision Survey of the D/H Ratio in the Nearby Interstellar Medium

We present high signal-to-noise ratio measurements of the H I Lyα absorption line toward 16 Galactic targets that are at distances between approximately 190 and 2200 pc, all beyond the wall of the Local Bubble. We describe the models used to remove stellar emission and absorption features and the methods used to account for all known sources of error in order to compute high-precision values of the H I column density with robust determinations of the uncertainties. When combined with H2 column densities from other sources, we find total H column densities ranging from 1020.01 to 1021.25 cm-2. Using deuterium column densities from Far Ultraviolet Spectroscopic Explorer observations we determine the D/H ratio along the sight lines. We confirm and strengthen the conclusion that D/H is spatially variable over these H I column density and target distance regimes, which predominantly probe the interstellar medium outside the Local Bubble. We discuss how these results affect models of Galactic chemical evolution. We also present an analysis of metal lines along the five sight lines for which we have high-resolution spectra and, along with results reported in the literature, discuss the corresponding column densities in the context of a generalized depletion analysis. We find that D/H is only weakly correlated with metal depletion and conclude that the spatial D/H variability is not solely due to dust depletion. A bifurcation of D/Htot as a function of depletion at high depletion levels provides modest support that deuterium-rich gas is infalling onto the Galactic plane.

Keywords: interstellar medium; galaxy chemical evolution
Temporal Evolution of Depolarization and Magnetic Field of Fast Radio Burst 20201124A

Fast radio bursts (FRBs) are energetic millisecond phenomena in the radio band. Polarimetric studies of repeating FRBs indicate that many of these sources occupy extreme and complex magnetoionized environments. Recently, a frequency-dependent depolarization has been discovered in several repeating FRBs. However, the temporal evolution of polarization properties is limited by the burst rate and observational cadence of telescopes. In this Letter, the temporal evolution of depolarization in repeating FRB 20201124A is explored. Using the simultaneous variation of rotation measure and dispersion measure, we also measure the strength of a magnetic field parallel to the line of sight. The strength ranges from a few μG to 103 μG. In addition, we find that the evolution of depolarization and magnetic field traces the evolution of rotation measure. Our result supports that the variation of depolarization, rotation measure, and the magnetic field are determined by the same complex magnetoionized screen surrounding the FRB source. The derived properties of the screen are consistent with the wind and the decretion disk of a massive star.

Keywords: radio transient sources; magnetic fields; interstellar medium; massive stars
New Constraints for Supernova Models from Presolar Silicon Carbide X Grains with Very High 26Al/27Al Ratios

We report C, N, Mg-Al, Si, and S isotope data of six 1-3 μm-sized SiC grains of Type X from the Murchison CM2 chondrite, believed to have formed in the ejecta of core-collapse supernova (CCSN) explosions. Their C, N, and Si isotopic compositions are fully compatible with previously studied X grains. Magnesium is essentially monoisotopic 26Mg which gives clear evidence for the decay of radioactive 26Al. Inferred initial 26Al/27Al ratios are between 0.6 and 0.78 which is at the upper end of previously observed ratios of X grains. Contamination with terrestrial or solar system Al apparently is low or absent, which makes the X grains from this study particularly interesting and useful for a quantitative comparison of Al isotope data with predictions from supernova models. The consistently high 26Al/27Al ratios observed here may suggest that the lower 26Al/27Al ratios of many X grains from the literature are the result of significant Al contamination and in part also of an improper quantification of 26Al. The real dispersion of 26Al/27Al ratios in X grains needs to be explored by future studies. The high observed 26Al/27Al ratios in this work provide a crucial constraint for the production of 26Al in CCSN models. We explored different CCSN models, including both "classical" and H ingestion CCSN models. It is found that the classical models cannot account for the high 26Al/27Al ratios observed here; in contrast, H ingestion models are able to reproduce the 26Al/27Al ratios along with C, N, and Si isotopic ratios reasonably well.

Keywords: circumstellar matter; meteorites; nucleosynthesis; supernovae
The Simons Observatory: The Large Aperture Telescope (LAT)

The Simons Observatory is a Cosmic Microwave Background experiment to observe the microwave sky in six frequency bands from 30 to 290 GHz. The Observatory—at ∼5200 m altitude—comprises three Small Aperture Telescopes and one Large Aperture Telescope (LAT) at the Atacama Desert, Chile. This research note describes the design and current status of the LAT along with its future timeline.

Keywords: observational cosmology; cosmic inflation; cosmic microwave background radiation; astronomical instrumentation; time domain astronomy; early universe
Photometric Objects Around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. II. Morphology, Color, and Size Dependences of the Stellar-Halo Mass Relation for Massive Galaxies

In this paper, we report a robust measurement of the morphology, color, and galaxy size dependences of the stellar-halo mass relation (SHMR) at the high-mass end (1011.3 M ⊙ < M ⋆ < 1011.7 M ⊙) at redshift z s ~ 0.6. 3 3 Throughout the paper, we use z s for redshift and z for the z-band magnitude. Applying our method, Photometric objects Around Cosmic webs (PAC), developed in a previous work to Baryon Oscillation Spectroscopic Survey and Hyper Suprime-cam Subaru Strategic Program observations, we measure the excess surface density ( ${\bar{n}}_{2}{w}_{p}({r}_{p})$ ) of satellites around massive central galaxies with different morphologies indicated by the Sérsic index n. We find that more compact (larger n) central galaxies are surrounded by more satellites. With the abundance matching method, we estimate the halo mass for the central galaxies and find that it increases monotonically with n, solid evidence for a morphology dependence of the SHMR. Specifically, our results show that most compact galaxies (n > 6) have a halo mass around 5.5 times larger than disk galaxies (n < 2). Similarly, using the effective radius R e and the rest-frame u - r color, we find that red (large) galaxies reside in halos that are in average 2.6 (2.3) times more massive than those hosting blue (small) galaxies.

Keywords: galaxy formation; galaxy dark matter halos
ALMA Detections of [O III] and [C II] Emission Lines From A1689-zD1 at z = 7.13

A1689-zD1 is one of the most distant galaxies, discovered with the aid of gravitational lensing, providing us with an important opportunity to study galaxy formation in the very early universe. In this study, we report the detection of [C II]158 μm and [O III]88 μm emission lines of A1689-zD1 in the Atacama Large Millimeter/submillimeter Array (ALMA) Bands 6 and 8. We measure the redshift of this galaxy as z sys = 7.133 ± 0.005 based on the [C II] and [O III] emission lines, consistent with that adopted by Bakx et al. The observed L [O III]/L [C II] ratio is 2.09 ± 0.09, higher than that of most of the local galaxies, but consistent with other z ~ 7 galaxies. The moderate spatial resolution of ALMA data provided us with a precious opportunity to investigate spatial variation of L [O III]/L [C II]. In contrast to the average value of 2.09, we find a much higher L [O III]/L [C II] of ~7 at the center of the galaxy. This spatial variation of L [O III]/L [C II] was seldom reported for other high-z galaxies. It is also interesting that the peak of the ratio does not overlap with optical peaks. Possible physical reasons include a central active galactic nucleus, shock heating from merging, and a starburst. Our moderate spatial resolution data also reveal that in addition to the observed two clumps shown in previous Hubble Space Telescope images, there is a redshifted segment to the west of the northern optical clump. This structure is consistent with previous claims that A1689-zD1 is a merging galaxy, but with the northern redshifted part being some ejected material, or that the northern redshifted material stems from a third more highly obscured region of the galaxy.

Keywords: high-redshift galaxies; galaxy kinematics; emission line galaxies; submillimeter astronomy
Physical Characterization of Moon Impactor WE0913A

On 2022 March 4, the object known as WE0913A crashed into the Moon after several close flybys of the Earth and the Moon in the previous three months. Leading up to impact, the identity of the lunar impactor was up for debate, with two possibilities: the Falcon 9 from the DSCOVR mission or the Long March 3C from the Chang'e 5-T1 mission. In this paper, we present a trajectory and spectroscopic analysis using ground-based telescope observations to show conclusively that WE0913A is the Long March 3C rocket body (R/B) from the Chang'e 5-T1 mission. Analysis of photometric light curves collected before impact give a spin period of 185.221 ± 6.540 s before the first close Earth flyby on 2022 January 20 and a period of 177.754 ± 0.779 s, both at a 1σ confidence level, before the second close Earth flyby on 2022 February 8. Using Markov Chain Monte Carlo sampling and a predictive light curve simulation based on an anisotropic Phong reflection model, we estimate both physical and dynamical properties of the Chang'e 5-T1 R/B at the start of an observation epoch. The results from the Bayesian analysis imply that there may have been additional mass on the front of the rocket body. Using our predicted impact location, the Lunar Reconnaissance Orbiter was able to image the crater site approximately 7.5 km from the prediction. Comparing the pre- and post-impact images of the location shows two distinct craters that were made, supporting the hypothesis that there was additional mass on the rocket body.

Keywords: lunar impacts; bayesian statistics; astrometry; orbit determination
Gyroresonance and Free-Free Radio Emissions from Multithermal Multicomponent Plasma

The solar atmosphere contains thermal plasma at a wide range of temperatures. This plasma is often quantified, in both observations and models, by a differential emission measure (DEM). The DEM is a distribution of the thermal electron density squared over temperature. In observations, the DEM is computed along a line of sight, while in the modeling it is over an elementary volume element (voxel). This description of the multithermal plasma is convenient and widely used in the analysis and modeling of extreme ultraviolet emission, which has an optically thin character. However, there is no corresponding treatment in the radio domain, where the optical depth of emission can be large, more than one emission mechanism is involved, and plasma effects are important. Here, we extend the theory of thermal gyroresonance and free-free radio emissions in the classical single-temperature Maxwellian plasma to the case of a multitemperature plasma. The free-free component is computed using the DEM and temperature-dependent ionization states of coronal ions, contributions from collisions of electrons with neutral atoms, the exact Gaunt factor, and the magnetic field effect. For the gyroresonant component, another measure of the multitemperature plasma is used, which describes the distribution of the thermal electron density over temperature. We give representative examples demonstrating important changes in the emission intensity and polarization due to the effects considered. The theory is implemented in available computer code.

Keywords: active sun; solar radio emission; solar coronal radio emission; solar magnetic fields; solar abundances; quiet sun
Composition and Sticking of Hot Chondritic Dust in a Protoplanetary Hydrogen Atmosphere

The sticking properties of dust in early phases of planet formation depend on the thermal history and ambient atmosphere. Therefore, dust will change its ability to build larger aggregates in collisions, depending on its location in protoplanetary disks. We aim at quantifying the change in sticking properties as chondritic dust is heated under various atmospheric conditions. In laboratory experiments, we milled two different meteorites (Sayh al Uhaymir 001 and Allende) to dust and formed millimeter-size cylinders. These cylindrical aggregates were sequentially heated from 600 to 1400 K in vacuum and in a hydrogen atmosphere, with compositional changes being tracked via Mössbauer spectroscopy. Using a Brazilian splitting test, the splitting tensile strength was determined. At higher temperatures, iron in silicates is reduced to metallic Fe(Ni) within the hydrogen atmosphere. In any case, adhesive forces are strongly increased by orders of magnitude from 1000 to 1400 K with minimum variations, depending on the atmospheric conditions. The dust in protoplanetary disks becomes ever more sticky, approaching a sublimation line upon exposure to temperatures of about 1400 K.

Keywords: protoplanetary disks; planet formation
Electromagnetic Ion Cyclotron Waves Pattern Recognition Based on a Deep Learning Technique: Bag-of-Features Algorithm Applied to Spectrograms

Several studies have shown the importance of electromagnetic ion cyclotron (EMIC) waves to the pitch angle scattering of energetic particles in the radiation belt, especially relativistic electrons, thus contributing to their net loss from the outer radiation belt to the upper atmosphere. The huge amount of data collected thus far provides us with the opportunity to use a deep learning technique referred to as the Bag-of-Features (BoF). When applied to images of magnetic field spectrograms in the frequency range of EMIC waves, the BoF allows us to distinguish, in a semi-automated way, several patterns in these spectrograms that can be relevant to describe physical aspects of EMIC waves. Each spectrogram image provided as an input to the BoF corresponds to the windowed Fourier transform of a ∼40 minutes to 1 hour interval of Van Allen Probes' high time-resolution vector magnetic field observations. Our data set spans the 2012 September 8 to 2016 December 31 period and is at geocentric distances larger than 3 Earth radii. A total of 66,204 spectrogram images are acquired in this interval, and about 45% of them, i.e., 30,190 images, are visually inspected to validate the BoF technique. The BoF's performance in identifying spectrograms with likely EMIC wave signatures is comparable to the visual inspection method, with the enormous advantage that the BoF technique greatly expedites the analysis by accomplishing the task in just a few minutes.

Keywords: planetary magnetospheres; neural networks; space plasmas; pp waves; support vector machine; classification
On the Comprehensive 3D Modeling of the Radiation Environment of Proxima Centauri b: A New Constraint on Habitability?

The combined influence of stellar energetic particles and galactic cosmic rays (GCRs) on the radiation environment, and hence potential habitability, of Earth-like exoplanets is relatively unknown. The present study, for the first time, comprehensively models the transport of these particles in a physics-first manner, using a unique suite of numerical models applied to the astrosphere of Proxima Centauri. The astrospheric plasma environment is modeled magnetohydrodynamically, while particle transport is modeled using a 3D ab initio GCR modulation code, as opposed to previous 1D approaches to this problem. StEP intensities are also calculated using observed stellar event profiles for Proxima Centauri as inputs. Computed intensities are then used to calculate possible atmospheric ionization effects and dose rates. We demonstrate that the contribution of GCRs to these quantities is indeed significant, contrary to the conclusions of previous studies. Furthermore, we propose a novel potential constraint on exoplanetary habitability, namely the rotational period of the host star, based on the unique 3D modeling approach presented here.

Keywords: astrospheres; exoplanet atmospheres; galactic cosmic rays; solar energetic particles
The Halo Mass-Temperature Relation for Clusters, Groups, and Galaxies

The halo mass-temperature (M-T) relation for a sample of 216 galaxy clusters, groups, and individual galaxies observed by the Chandra X-ray Observatory is presented. Using accurate spectral measurements of their hot atmospheres, we derive the M-T relation for systems with temperatures ranging between 0.4 and 15.0 keV. We measure the total masses of the clusters, groups, and galaxies at radius R 2500, finding that the M 2500 ∝ T α relation follows a power law with α = 1.65 ± 0.06. Our relation agrees with recent lensing studies of the M-T relation at R 200 and is consistent with self-similar theoretical predictions and recent simulations. This agreement indicates that the M-T relation is weakly affected by nongravitational heating processes. Using lensing masses within R 200 we find M 200-T follows a power law with a slope of 1.61 ± 0.19, consistent with the M 2500-T relation. No evidence for a break or slope change is found in either relation. Potential biases associated with sample selection, evolution, and the assumption of hydrostatic equilibrium that may affect the scaling are examined. No significant impacts attributable to these biases are found. Non-cool-core clusters and early spirals produce higher scatter in the M-T relation than cool-core clusters and elliptical galaxies.

Keywords: galaxy clusters