adsabs/SciX_UAT_keywords huggingface dataset:
B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). I. The Massive Filament G11.11-0.12 Observed by SOFIA/HAWC+

We report the first measurement of polarized thermal dust emission toward the entire infrared dark cloud G11.11-0.12 taken by the polarimeter SOFIA/HAWC+ at 214 μm. The obtained magnetic fields (B-fields) from the polarized emission of the early-stage and massive filament tend to be perpendicular to its spine. We produce a map of B-field strengths for the center region of the filament. The strengths vary in the range of 100-600 μG and are strongest along the filament's spine. The central region is sub-Alfvénic and mostly subcritical, meaning that B-fields dominate over turbulence and are strong enough to resist gravitational collapse. The alignment and properties of dust grains in the filament are studied using radiative torque (RAT) theory. We find the decrease of polarization degree P with emission intensity I, i.e., depolarization effect, of the form P ∝ I -α with α ~ 0.8-0.9, implying a significant loss of grain alignment in the filament's spine. The depolarization can be explained by the decrease in RAT alignment efficiency toward the denser regions with weaker radiation field, which cannot be explained by B-field tangling. We study the effect of the enhanced magnetic relaxation by embedded iron inclusions on RAT alignment and find that the high polarization fraction P ~ 20%-30% in the outer layer of the filament is potential evidence for the magnetically enhanced RAT alignment mechanism. This is the first time this effect is evaluated in a filament. Based on the polarization fraction and RAT alignment theory, we also find evidence for grain growth in the filament.

Keywords: interstellar magnetic fields; interstellar filaments; star forming regions; star formation; far infrared astronomy; interstellar dust; interstellar medium
The Curious Case of PHL 293B: A Long-lived Transient in a Metal-poor Blue Compact Dwarf Galaxy

We report on small-amplitude optical variability and recent dissipation of the unusually persistent broad emission lines in the blue compact dwarf galaxy PHL 293B. The galaxy's unusual spectral features (P Cygni-like profiles with ∼800 km s-1 blueshifted absorption lines) have resulted in conflicting interpretations of the nature of this source in the literature. However, analysis of new Gemini spectroscopy reveals the broad emission has begun to fade after being persistent for over a decade prior. Precise difference imaging light curves constructed with the Sloan Digital Sky Survey and the Dark Energy Survey reveal small-amplitude optical variability of ∼0.1 mag in the g band offset by 100 ± 21 pc from the brightest pixel of the host. The light curve is well-described by an active galactic nuclei (AGN)-like damped random walk process. However, we conclude that the origin of the optical variability and spectral features of PHL 293B is due to a long-lived stellar transient, likely a Type IIn supernova or nonterminal outburst, mimicking long-term AGN-like variability. This work highlights the challenges of discriminating between scenarios in such extreme environments, relevant to searches for AGNs in dwarf galaxies. This is the second long-lived transient discovered in a blue compact dwarf, after SDSS1133. Our result implies such long-lived stellar transients may be more common in metal-deficient galaxies. Systematic searches for low-level variability in dwarf galaxies will be possible with the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory.

Keywords: type ii supernovae; transient detection; luminous blue variable stars; blue compact dwarf galaxies; dwarf galaxies; galaxies
The Missing Symbiotic Stars: A Joint Analysis with Gaia, GALEX, and XMM-Newton Data

The existence of a population of low-accretion-rate symbiotic stars (SySts), consisting of a giant star and a compact companion (usually a white dwarf), has been proposed recently. However, their population has not been fully understood. In this work, we present an investigation on SySts candidates consisting of asymptotic giant branch stars (AGBs) by cross-correlating the Gaia DR3, the Galaxy Evolution Explorer All-Sky Imaging Survey, and the 4XMM DR13 catalogs. We first build a sample of AGBs within 500 pc based on their locations in the Gaia color–absolute magnitude diagram. We then explore the UV and X-ray properties of the sampled AGBs and compare them to known SySts and candidates. We find 10 SySts candidates based on the far-ultraviolet excess. The typical UV luminosity of the candidates is 1031 erg s‑1, which corresponds to a typical accretion rate of 10‑12–10‑11 M ⊙ yr‑1, which is more than 1 order of magnitude lower than known SySts. Based on these findings, the total number of SySts within 500 pc is estimated to be 18. The number of AGBs with X-ray flux above 10‑14 erg s‑1 cm‑2 within 500 pc is estimated to be 37. Our finding implies that a large number of low-accretion-rate SySts are yet to be detected, which provides a base for a complete understanding of their population.

Keywords: symbiotic binary stars; ultraviolet sources
Contaminante: A Tool for Automatically Finding a Close-to-optimal Aperture for Transiting Signals in Kepler, K2, and TESS Data

Together, NASA's Kepler/K2 and TESS missions have produced image data and time-series of millions of stars. These data have been used to identify thousands of transiting planet candidates. Unfortunately, some transiting signals do not originate from the target of the mission, and instead originate from background or blended eclipsing binaries. Exoplanet candidates can be vetted by searching for evidence that a detected transiting signal originates outside of the aperture. Centroiding tests, such as those employed by the Kepler Pipeline, have proved useful for vetting exoplanet candidates which have been falsely identified due to background contamination. However, centroiding tests are not able to provide a light curve of the true transiting target, which is valuable for vetting the origin of the signal. We present the contaminante Python tool which, given Kepler/K2 or TESS data, automatically builds a pixel aperture (An aperture is defined as a contiguous selection of pixels in a stack of imagettes, known as a Target Pixel File.) that maximizes the transiting signal at a given period, transit mid point and duration. In this research note, we describe the procedure we use to determine that optimal aperture, and show a demonstration of the contaminante tool on a Kepler false positive.

Keywords: time series analysis; exoplanets; astronomy data analysis
BASS. XLII. The Relation between the Covering Factor of Dusty Gas and the Eddington Ratio in Nearby Active Galactic Nuclei

Accreting supermassive black holes (SMBHs) located at the centers of galaxies are typically surrounded by large quantities of gas and dust. The structure and evolution of this circumnuclear material can be studied at different wavelengths, from the submillimeter to the X-ray. Recent X-ray studies have shown that the covering factor of the obscuring material tends to decrease with increasing Eddington ratio, likely due to radiative feedback on dusty gas. Here we study a sample of 549 nearby (z ≲ 0.1) hard X-ray (14-195 keV) selected nonblazar active galactic nuclei (AGN) and use the ratio between the AGN infrared and bolometric luminosity as a proxy of the covering factor. We find that, in agreement with what has been found by X-ray studies of the same sample, the covering factor decreases with increasing Eddington ratio. We also confirm previous findings that showed that obscured AGN typically have larger covering factors than unobscured sources. Finally, we find that the median covering factors of AGN located in different regions of the column density-Eddington ratio diagram are in good agreement with what would be expected from a radiation-regulated growth of SMBHs.

Keywords: active galaxies; seyfert galaxies; infrared photometry; x-ray astronomy; quasars
Highly Depleted Alkali Metals in Jupiter's Deep Atmosphere

Water and ammonia vapors are known to be the major sources of spectral absorption at pressure levels observed by the microwave radiometer (MWR) on Juno. However, the brightness temperatures and limb darkening observed by the MWR at its longest-wavelength channel of 50 cm (600 MHz) in the first nine perijove passes indicate the existence of an additional source of opacity in the deep atmosphere of Jupiter (pressures beyond 100 bar). The absorption properties of ammonia and water vapor, and their relative abundances in Jupiter's atmosphere, do not provide sufficient opacity in the deep atmosphere to explain the 600 MHz channel observation. Here we show that free electrons due to the ionization of alkali metals, i.e., sodium and potassium, with subsolar metallicity, [M/H] (log-based 10 relative concentration to solar) in the range of [M/H] = -2 to [M/H] = -5, can provide the missing source of opacity in the deep atmosphere. If the alkali metals are not the source of additional opacity in the MWR data, then their metallicity at 1000 bars can only be even lower. This upper bound of -2 on the metallicity of the alkali metals contrasts with the other heavy elements-C, N, S, Ar, Kr, and Xe-that are all enriched relative to their solar abundances, having a metallicity of approximately +0.5.

Keywords: chemical abundances; jupiter; solar system; extrasolar gaseous giant planets
The Mechanism of Efficient Electron Acceleration at Parallel Nonrelativistic Shocks

Thermal electrons cannot directly participate in the process of diffusive acceleration at electron-ion shocks because their Larmor radii are smaller than the shock transition width: this is the well-known electron injection problem of diffusive shock acceleration. Instead, an efficient pre-acceleration process must exist that scatters electrons off of electromagnetic fluctuations on scales much shorter than the ion gyroradius. The recently found intermediate-scale instability provides a natural way to produce such fluctuations in parallel shocks. The instability drives comoving (with the upstream plasma) ion-cyclotron waves at the shock front and only operates when the drift speed is smaller than half of the electron Alfvén speed. Here we perform particle-in-cell simulations with the SHARP code to study the impact of this instability on electron acceleration at parallel nonrelativistic, electron-ion shocks. To this end, we compare a shock simulation in which the intermediate-scale instability is expected to grow to simulations where it is suppressed. In particular, the simulation with an Alfvénic Mach number large enough to quench the intermediate instability shows a great reduction (by two orders of magnitude) of the electron acceleration efficiency. Moreover, the simulation with a reduced ion-to-electron mass ratio (where the intermediate instability is also suppressed) not only artificially precludes electron acceleration but also results in erroneous electron and ion heating in the downstream and shock transition regions. This finding opens up a promising route for a plasma physical understanding of diffusive shock acceleration of electrons, which necessarily requires realistic mass ratios in simulations of collisionless electron-ion shocks.

Keywords: shocks; supernova remnants
Evolutionary Status of Selected Post-AGB Stars Based on Gaia DR3

The evolutionary status of 24 post-AGB stars is presented based on Gaia DR3 data. All 24 stars have parallaxes accurate to better than 3σ and have RUWE values <1.4. Based on the Gaia DR3 distances the absolute luminosities are derived. For 14 of the stars, the luminosities confirm their post-AGB evolutionary stage. However, V1027 Cyg, which was previously classified as a post-AGB star, is found to have a higher luminosity than would be expected if it was truly a post-AGB star; thus it may be an evolved, massive, pulsating semi-regular variable star of type G7Ia. For 9 of the stars, the luminosities are lower than 1000 L ⊙, indicating that some are post-HB stars and some are post-RGB stars.

Keywords: post-asymptotic giant branch stars
The Simons Observatory Large Aperture Telescope Receiver

The Simons Observatory is a ground-based cosmic microwave background experiment that consists of three 0.4 m small-aperture telescopes and one 6 m Large Aperture Telescope, located at an elevation of 5300 m on Cerro Toco in Chile. The Simons Observatory Large Aperture Telescope Receiver (LATR) is the cryogenic camera that will be coupled to the Large Aperture Telescope. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date, with a diameter of 2.4 m and a length of 2.6 m. The coldest stage of the camera is cooled to 100 mK, the operating temperature of the bolometric detectors with bands centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will accommodate 13 40 cm diameter optics tubes, each with three detector wafers and a total of 62,000 detectors. The LATR design must simultaneously maintain the optical alignment of the system, control stray light, provide cryogenic isolation, limit thermal gradients, and minimize the time to cool the system from room temperature to 100 mK. The interplay between these competing factors poses unique challenges. We discuss the trade studies involved with the design, the final optimization, the construction, and ultimate performance of the system.

Keywords: cmbr detectors; cosmic microwave background radiation; observational cosmology; ground-based astronomy; ground telescopes; observatories; astronomical instrumentation
Modeling the Central Supermassive Black Hole Mass of Quasars via the LSTM Approach

One of the fundamental questions about quasars is related to their central supermassive black holes. The reason for the existence of these black holes with such a huge mass is still unclear, and various models have been proposed to explain them. However, there is still no comprehensive explanation that is accepted by the community. The only thing we are sure of is that these black holes were not created by the collapse of giant stars or the accretion of matter around them. Moreover, another important question is related to the mass distribution of these black holes over time. Observations have shown that if we go back through redshift, we see black holes with more mass, and after passing the peak of star formation redshift, this procedure decreases. Nevertheless, the exact redshift of this peak is still controversial. In this paper, with the help of deep learning and the LSTM algorithm, we try to find a suitable model for the mass of the central black holes of quasars over time by considering both the QUOTAS and QuasarNET data sets. Our model was built with these data reported from redshift 3 to 7 and for two redshift intervals, 0-3 and 7-10, and it predicted the mass of the quasars' central supermassive black holes. We have also tested our model for the specified intervals with observed data from central black holes and discussed the results.

Keywords: quasars
CMB Cold Spot in the Planck Light

The Cold Spot, with an unusually cold region surrounded by a hot ring, is a statistically significant anomaly in the cosmic microwave background (CMB) sky. In this work we assess whether different sets of multiple subvoids based on the 2dF-VST ATLAS Cold Spot galaxy redshift survey or a collapsing cosmic texture could have produced such an anomaly through a simultaneous search for their gravitational redshift and lensing signatures on the Planck CMB temperature anisotropies. We use patches with radii R = 10° and R = 20° to account for the inner cold region as well as the outer hot ring. As the void model, we explore two sets of ΛLTB templates characterized by different values of the model's free parameters, and a top-hat void template. We detect higher than expected gravitational redshift amplitudes for the first two sets, ${{ \mathcal A }}_{\mathrm{rs}}=5.4\pm 1.4$ and ${{ \mathcal A }}_{\mathrm{rs}}=14.4\pm 3.8$ , and lower than expected for the top-hat model, ${{ \mathcal A }}_{\mathrm{rs}}=0.3\pm 0.1$ . The amplitudes for the lensing imprint are consistent with zero for all these subvoid models. The estimated amplitude for the texture imprint from the gravitational redshift measurement implies the energy scale of the texture, parameterized by ɛ, to be ɛ = (7.6 ± 2.0) × 10-5, with no detection of the lensing trace. We note that the deviation of the subvoid amplitudes from unity and the inability of the texture and some of the void profiles to reproduce the hot ring indicate theoretical insufficiencies, either in the construction of the model or in the assumed gravitational and cosmological framework leading to the imprints for the structures.

Keywords: cosmic microwave background radiation; astronomy data acquisition; observational cosmology; cosmology; astronomy data analysis
Broadband High-energy Emission of the Gamma-Ray Binary System LS 5039: Spectral and Temporal Features Using NuSTAR and Fermi Observations

We report a detailed analysis of the hard X-ray and GeV gamma-ray spectra of LS 5039, one of the brightest gamma-ray binary system in the Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) observation covering its entire orbit in 2016 allowed us for the first time to study the orbital variability of the spectrum above 10 keV. The hard X-ray spectrum is well described with a single power-law component up to 78 keV. The X-ray flux showed a slight deviation from those observed previously with Suzaku in 2007. The fast X-ray brightening observed with Suzaku, around the inferior conjunction, was not observed in this observation. We also analyzed 11 yr of Fermi Large Area Telescope data of LS 5039. The GeV spectrum around the inferior conjunction was well described with two nonthermal components: a power law with a photon index of ~3 and a cutoff power law with a cutoff energy of ~2 GeV. The orbital flux variability also changed gradually around a few GeV. These results indicate that there are two emission components in the GeV band, and the dominant component above ~1 GeV does not depend on the orbital phase. By combining these results, we update the spectral energy distribution of LS 5039 with the highest available statistics. Theoretical models proposed so far cannot explain the obtained multiwavelength spectrum, especially the emission from ~1 to ~400 MeV, and we discuss the possibility that particle acceleration in LS 5039 is different from the shock acceleration.

Keywords: compact binary stars; x-ray binary stars; gamma-ray sources; x-ray sources; high mass x-ray binary stars
Mixing the Solar Wind Proton and Electron Scales. Theory and 2D-PIC Simulations of Firehose Instability

Firehose-like instabilities (FIs) are cited in multiple astrophysical applications. Of particular interest are the kinetic manifestations in weakly collisional or even collisionless plasmas, where these instabilities are expected to contribute to the evolution of macroscopic parameters. Relatively recent studies have initiated a realistic description of FIs, as induced by the interplay of both species, electrons and protons, dominant in the solar wind plasma. This work complements the current knowledge with new insights from linear theory and the first disclosures from 2D-PIC simulations, identifying the fastest growing modes near the instability thresholds and their long-run consequences on the anisotropic distributions. Thus, unlike previous setups, these conditions are favorable to those aperiodic branches that propagate obliquely to the uniform magnetic field, with (maximum) growth rates higher than periodic, quasi-parallel modes. Theoretical predictions are, in general, confirmed by the simulations. The aperiodic electron FI (a-EFI) remains unaffected by the proton anisotropy, and saturates rapidly at low-level fluctuations. Regarding the FI at proton scales, we see a stronger competition between the periodic and aperiodic branches. For the parameters chosen in our analysis, the aperiodic proton FI (a-PFI) is excited before than the periodic proton FI (p-PFI), with the latter reaching a significantly higher fluctuation power. However, both branches are significantly enhanced by the presence of anisotropic electrons. The interplay between EFIs and PFIs also produces a more pronounced proton isotropization.

Keywords: space plasmas; solar wind; plasma astrophysics
On the Nature of Disks at High Redshift Seen by JWST/CEERS with Contrastive Learning and Cosmological Simulations

Visual inspections of the first optical rest-frame images from JWST have indicated a surprisingly high fraction of disk galaxies at high redshifts. Here, we alternatively apply self-supervised machine learning to explore the morphological diversity at z ≥ 3. Our proposed data-driven representation scheme of galaxy morphologies, calibrated on mock images from the TNG50 simulation, is shown to be robust to noise and to correlate well with the physical properties of the simulated galaxies, including their 3D structure. We apply the method simultaneously to F200W and F356W galaxy images of a mass-complete sample (M */M ⊙ > 109) at 3 ≤ z ≤ 6 from the first JWST/NIRCam CEERS data release. We find that the simulated and observed galaxies do not exactly populate the same manifold in the representation space from contrastive learning. We also find that half the galaxies classified as disks—either convolutional neural network-based or visually—populate a similar region of the representation space as TNG50 galaxies with low stellar specific angular momentum and nonoblate structure. Although our data-driven study does not allow us to firmly conclude on the true nature of these galaxies, it suggests that the disk fraction at z ≥ 3 remains uncertain and possibly overestimated by traditional supervised classifications. Deeper imaging and spectroscopic follow-ups as well as comparisons with other simulations will help to unambiguously determine the true nature of these galaxies, and establish more robust constraints on the emergence of disks at very high redshift.

Keywords: galaxy formation; galaxy evolution; high-redshift galaxies; neural networks
The Role of Complex Ionized Absorbers in the Soft X-Ray Spectra of Intermediate Polars

In magnetic cataclysmic variables (mCVs), X-ray radiation originates from a shock-heated, multi-temperature plasma in the post-shock region near the white dwarf's surface. These X-rays are modified by a complex distribution of absorbers in the pre-shock region. The presence of photoionized lines and warm absorber features in the soft X-ray spectra of these mCVs suggests that these absorbers are ionized. We developed the ionized complex absorber model zxipab, which is represented by a power-law distribution of ionized absorbers in the pre-shock flow. Using the ionized absorber model zxipab along with a cooling flow model with a reflection component, we model the broadband Chandra/High-Energy Transmission Grating (HETG) and Nuclear Spectroscopic Telescope Array (NuSTAR) spectra of two intermediate polars (IPs): NY Lup and V1223 Sgr. We find that this model describes well many of the H- and He-like emission lines from medium-Z elements, which arise from a collisionally excited plasma. However the model fails to account for some of the He-like triplets from the medium-Z elements, which points toward their photoionized origin. We do not find compelling evidence for a blackbody component to model the soft excess seen in the residuals of the Chandra/HETG spectra, which could be due to uncertainties in the estimation of the interstellar absorption of these sources using the Chandra/HETG data and/or excess fluxes seen in some photoionized emission lines which are not accounted for by the cooling flow model. We describe the implications of this model with respect to the geometry of the pre-shock region for these two IPs.

Keywords: cataclysmic variable stars; white dwarf stars; astronomy data analysis