adsabs/SciX_UAT_keywords huggingface dataset:
SiO Outflows as Tracers of Massive Star Formation in Infrared Dark Clouds

To study the early phases of massive star formation, we present ALMA observations of SiO(5-4) emission and VLA observations of 6 cm continuum emission toward 32 Infrared Dark Cloud clumps, spatially resolved down to ≲0.05 pc. Out of the 32 clumps, we detect SiO emission in 20 clumps, and in 11 of them the SiO emission is relatively strong and likely tracing protostellar outflows. Some SiO outflows are collimated, while others are less ordered. For the six strongest SiO outflows, we estimate basic outflow properties. In our entire sample, where there is SiO emission, we find 1.3 mm continuum and infrared emission nearby, but not vice versa. We build the spectral energy distributions (SEDs) of cores with 1.3 mm continuum emission and fit them with radiative transfer models. The low luminosities and stellar masses returned by SED fitting suggest these are early-stage protostars. We see a slight trend of increasing SiO line luminosity with bolometric luminosity, which suggests more powerful shocks in the vicinity of more massive YSOs. We do not see a clear relation between the SiO luminosity and the evolutionary stage indicated by L/M. We conclude that, as a protostar approaches a bolometric luminosity of ~102 L⊙, the shocks in the outflow are generally strong enough to form SiO emission. The VLA 6 cm observations toward the 15 clumps with the strongest SiO emission detect emission in four clumps, which is likely from shock-ionized jets associated with the more massive ones of these protostellar cores.

Keywords: massive stars; star formation; interstellar line emission; infrared dark clouds; radio continuum emission; shocks; protostars; submillimeter astronomy; jets
SDSS-IV MaStar: Data-driven Parameter Derivation for the MaStar Stellar Library

The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Stellar Library (MaStar) is a large collection of high-quality empirical stellar spectra designed to cover all spectral types and ideal for use in the stellar population analysis of galaxies observed in the MaNGA survey. The library contains 59,266 spectra of 24,130 unique stars with spectral resolution R ~ 1800 and covering a wavelength range of 3622-10,354 Å. In this work, we derive five physical parameters for each spectrum in the library: effective temperature (T eff), surface gravity ( $\mathrm{log}g$ ), metallicity ([Fe/H]), microturbulent velocity ( $\mathrm{log}({v}_{\mathrm{micro}})$ ), and alpha-element abundance ([α/Fe]). These parameters are derived with a flexible data-driven algorithm that uses a neural network model. We train a neural network using the subset of 1675 MaStar targets that have also been observed in the Apache Point Observatory Galactic Evolution Experiment (APOGEE), adopting the independently-derived APOGEE Stellar Parameter and Chemical Abundance Pipeline parameters for this reference set. For the regions of parameter space not well represented by the APOGEE training set (7000 ≤ T ≤ 30,000 K), we supplement with theoretical model spectra. We present our derived parameters along with an analysis of the uncertainties and comparisons to other analyses from the literature.

Keywords: spectroscopy; fundamental parameters of stars; stellar abundances; astronomy data analysis; astrostatistics; surveys
Global Kinetic Modeling of the Intrabinary Shock in Spider Pulsars

Spider pulsars are compact binary systems composed of a millisecond pulsar and a low-mass companion. The relativistic magnetically dominated pulsar wind impacts onto the companion, ablating it and slowly consuming its atmosphere. The interaction forms an intrabinary shock, a proposed site of particle acceleration. We perform global fully kinetic particle-in-cell simulations of the intrabinary shock, assuming that the pulsar wind consists of plane-parallel stripes of alternating polarity and that the shock wraps around the companion. We find that particles are efficiently accelerated via shock-driven reconnection. We extract first-principles synchrotron spectra and light curves, which are in good agreement with X-ray observations: (1) the synchrotron spectrum is nearly flat, F ν ∝ const; (2) when the pulsar spin axis is nearly aligned with the orbital angular momentum, the light curve displays two peaks, just before and after the pulsar eclipse (pulsar superior conjunction), separated in phase by ~0.8 rad; (3) the peak flux exceeds the one at the inferior conjunction by a factor of 10.

Keywords: pulsars; non-thermal radiation sources; shocks; high energy astrophysics
Exploring the Mpc Environment of the Quasar ULAS J1342+0928 at z = 7.54

Theoretical models predict that z ≳ 6 quasars are hosted in the most massive halos of the underlying dark matter distribution and thus would be immersed in protoclusters of galaxies. However, observations report inconclusive results. We investigate the 1.1 proper-Mpc2 environment of the z = 7.54 luminous quasar ULAS J1342+0928. We search for Lyman-break galaxy (LBG) candidates using deep imaging from the Hubble Space Telescope (HST) in the Advanced Camera for Surveys (ACS)/F814W, Wide Field Camera 3 (WFC3)/F105W/F125W bands, and Spitzer/Infrared Array Camera at 3.6 and 4.5 μm. We report a ${z}_{\mathrm{phot}}={7.69}_{-0.23}^{+0.33}$ LBG with magF125W = 26.41 at 223 projected proper kpc (pkpc) from the quasar. We find no HST counterpart to one [C II] emitter previously found with the Atacama Large millimeter/submillimeter Array (ALMA) at 27 projected pkpc and z [C II]=7.5341 ± 0.0009 (Venemans et al. 2020). We estimate the completeness of our LBG candidates using results from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey/GOODS deep blank field searches sharing a similar filter setup. We find that >50% of the z ∼ 7.5 Lyman-break galaxies (LBGs) with magF125W > 25.5 are missed due to the absence of a filter redward of the Lyman break in F105W, hindering the UV color accuracy of the candidates. We conduct a QSO-LBG clustering analysis revealing a low LBG excess of ${0.46}_{-0.08}^{+1.52}$ in this quasar field, consistent with an average or low-density field. Consequently, this result does not present strong evidence of an LBG overdensity around ULAS J1342+0928. Furthermore, we identify two LBG candidates with a z phot matching a confirmed z = 6.84 absorber along the line of sight to the quasar. All these galaxy candidates are excellent targets for follow-up observations with JWST and/or ALMA to confirm their redshift and physical properties.

Keywords: quasars; quasar-galaxy pairs; galaxies; high-redshift galaxies; lyman-break galaxies
A Negative Long Lag from the Optical to the UV Continuum in Fairall 9

We report the detection of a long-timescale negative lag, where the blue bands lag the red bands, in the nearby Seyfert 1 galaxy Fairall 9, with two independent methods. Active Galactic Nuclei (AGNs) light curves show variability over a wide range of timescales. By measuring time lags between different wavelengths, the otherwise inaccessible structure and kinematics of the accretion disk can be studied. One common approach, reverberation mapping, quantifies the continuum and line lags moving outward through the disk at the light-travel time, revealing the size and temperature profile of the disk. Inspired by numerical simulations, we expect longer lags to exist in AGN light curves that travel inward on longer timescales, tracing the accretion process itself. By analyzing AGN light curves in both temporal and frequency space, we report the detection of long-timescale lags (~-70 days) in Fairall 9 that propagate in the opposite direction to the reverberation lag. The short continuum lag (<10 days) is also detected and is consistent with reverberation lags reported in the literature. When fitting the longer lag as a function of frequency with a model motivated by the thin disk model, we find that the disk scale height likely increases outward in the disk. This detection raises the exciting prospect of mapping accretion disk structures across a wide range of AGN parameters.

Keywords: accretion; active galactic nuclei; black hole physics; black holes; seyfert galaxies; supermassive black holes
Probabilistic Association of Transients to their Hosts (PATH)

We introduce a new method to estimate the probability that an extragalactic transient source is associated with a candidate host galaxy. This approach relies solely on simple observables: sky coordinates and their uncertainties, galaxy fluxes, and angular sizes. The formalism invokes Bayes' rule to calculate the posterior probability $P\left({O}_{i}| x\right)$ from the galaxy prior P(O), observables x, and an assumed model for the true distribution of transients in/around their host galaxies. Using simulated transients placed in the well-studied Cosmic Evolution Survey field, we consider several agnostic and physically motivated priors and offset distributions to explore the method sensitivity. We then apply the methodology to the set of 13 fast radio bursts (FRBs) localized with an uncertainty of several arcseconds. Our methodology finds nine of these are securely associated to a single host galaxy, $P\left({O}_{i}| x\right)\gt 0.95$ . We examine the observed and intrinsic properties of these secure FRB hosts, recovering distributions similar to those found in previous works. Furthermore, we find a strong correlation between the apparent magnitude of the securely identified host galaxies and the estimated cosmic dispersion measures of the corresponding FRBs, which results from the Macquart relation. Future work with FRBs will leverage this relation and other measures from the secure hosts as priors for future associations. The methodology is generic to transient type, localization error, and image quality. We encourage its application to other transients where host galaxy associations are critical to the science, e.g., gravitational wave events, gamma-ray bursts, and supernovae. We have encoded the technique in Python on GitHub: https://github.com/FRBs/astropath.

Keywords: radio transient sources; bayes' theorem
Effects of the Galactic Magnetic Field on the UHECR Correlation Studies with Starburst Galaxies

We estimate the biases caused by the coherent deflection of cosmic rays due to the Galactic magnetic field (GMF) in maximum likelihood analyses for searches of ultrahigh-energy cosmic-ray sources in the literature. We simulate mock event data sets with a set of assumptions for the starburst galaxy source model, coherent deflection by a GMF model, and mixed-mass composition. We then conduct a maximum likelihood analysis without accounting for the GMF in the same manner as previous studies. We find that the anisotropic fraction f ani is estimated to be systematically lower than the true value. We estimate the true parameters that are compatible with the best-fit parameters that were reported, and find that except for a narrow region with a large anisotropic fraction and a small separation angular scale, a wide parameter space is still compatible with the experimental results. We also develop a maximum likelihood method that takes the GMF model into account and confirm in Monte Carlo simulations that we can estimate the true parameters within a 1σ contour under the ideal condition that we know the event-by-event mass and the GMF.

Keywords: cosmic ray astronomy; cosmic ray sources; cosmic rays; ultra-high-energy cosmic radiation
An Accurate Analytic Mass Model for Lensing Galaxies

We develop an analytic mass model for lensing galaxies, based on a broken power-law density profile, which is a power-law profile with a mass deficit or surplus in the central region. Under the assumption of an elliptically symmetric surface mass distribution, the deflection angle and magnification can be evaluated analytically for this new model. We compute the theoretical prediction for various quantities, including the volume and surface mass density profiles of the galaxies, and the aperture and luminosity-weighted line-of-sight velocity dispersions, and compare them to those measured from the Illustris simulation. We find an excellent agreement between our model prediction and the simulation, which validates our modeling. The high efficiency and accuracy of our model manifests itself as a promising tool for studying properties of galaxies with strong lensing.

Keywords: strong gravitational lensing; dark matter; cosmology; galaxy dynamics; galaxy dark matter halos; gravitational lensing; galaxy mass distribution
A Unique Resource for Solar Flare Diagnostic Studies: The SMM Bent Crystal Spectrometer

The Bent Crystal Spectrometer (BCS) on the NASA Solar Maximum Mission spacecraft observed the X-ray spectra of numerous solar flares during the periods 1980 February-November and 1984-1989. The instrument, the first of its kind to use curved crystal technology, observed the resonance lines of He-like Ca (Ca XIX) and Fe (Fe XXV), and neighboring satellite lines, allowing the study of the rapid evolution of flare plasma temperature, turbulence, mass motions etc. To date there has not been a solar X-ray spectrometer with comparable spectral and time resolution, while subsequent solar cycles have delivered far fewer and less intense flares. The BCS data archive thus offers an unparalleled resource for flare studies. A recent reassessment of the BCS calibration and its operations is extended here by using data during a spacecraft scan in the course of a flare on 1980 November 6 that highlights small deformations in the crystal curvature of the important channel 1 (viewing lines of Ca XIX and satellites). The results explain long-standing anomalies in spectral line ratios which have been widely discussed in the past. We also provide an in-flight estimation of the BCS collimator field of view which improves the absolute intensity calibration of the BCS. The BCS channel 1 background is shown to be entirely due to solar continuum radiation, confirming earlier analyses implying a time-variable flare abundance of Ca. We suggest that BCS high-resolution Ca XIX and Fe XXV line spectra be used as templates for the analysis of X-ray spectra of nonsolar sources.

Keywords: solar x-ray emission; solar x-ray flares
Non-Boussinesq Low-Prandtl-number Convection with a Temperature-dependent Thermal Diffusivity

In an attempt to understand the role of the strong radial dependence of thermal diffusivity on the properties of convection in Sun-like stars, we mimic that effect in non-Oberbeck-Boussinesq convection in a horizontally extended rectangular domain (aspect ratio 16) by allowing the thermal diffusivity κ to increase with the temperature (as in the case of stars). Direct numerical simulations (i.e., numerical solutions of the governing equations by resolving up to the smallest scales without requiring any modeling) show that, in comparison with Oberbeck-Boussinesq simulations (two of which we perform for comparison purposes), the symmetry of the temperature field about the mid-horizontal plane is broken, whereas the velocity and heat flux profiles remain essentially symmetric. Our choice of κ(T), which resembles the variation in stars, results in a temperature field that loses its fine structures toward the hotter part of the computational domain, but the characteristic large scale of the turbulent thermal "superstructures," which are structures whose size is typically larger than the depth of the convection domain, continues to be largely independent of the depth.

Keywords: solar convective zone; stellar convective zones
Reevaluation of C4H Abundance Based on the Revised Dipole Moment

Abnormally large column densities of the carbon-chain molecule, C4H, have been reported in various sources. The main reason for this was supposed to be an underestimated value of the permanent dipole moment of C4H. C4H has a low-lying electronic excited state of 2Π with a large dipole moment in the previous quantum chemical calculations. However, the mixing of the excited state with the ground state 2Σ+ has not been taken into consideration. In the present study, we evaluated this mixing by introducing a multireference configuration interaction. The effective dipole moment of C4H in the ground state was calculated to be 2.10 D, which is about 2.4 times larger than the values used so far. Revised column densities of C4H in dark clouds, low-mass star-forming regions, and the circumstellar envelope IRC+10216 based upon the new value are about a factor of 6 smaller than the previous values. With the revised column densities, exponential smooth decreases are found for the abundances of the C2nH (n = 1-4) molecules with carbon-chain length in these sources, suggesting high similarities among individual formation mechanisms of the C2nH molecules.

Keywords: astrochemistry; abundance ratios; interstellar molecules; circumstellar envelopes; star forming regions; interstellar clouds
A Bright Fast Radio Burst from FRB 20200120E with Sub-100 Nanosecond Structure

We have detected a bright radio burst from FRB 20200120E with the NASA Deep Space Network (DSN) 70 m dish (DSS-63) at radio frequencies between 2.2 and 2.3 GHz. This repeating fast radio burst (FRB) is reported to be associated with a globular cluster in the M81 galactic system. With high time resolution recording, low scattering, and large intrinsic brightness of the burst, we find a burst duration of ~30 μs, comprised of several narrow components with typical separations of 2-3 μs. The narrowest component has a width of ≲100 ns, which corresponds to a light travel time size as small as 30 m. The peak flux density of the narrowest burst component is 270 Jy. We estimate the total spectral luminosity of the narrowest component of the burst to be 4 × 1030 erg s-1 Hz-1, which is a factor of ~500 above the luminosities of the so-called "nanoshots" associated with giant pulses from the Crab pulsar. This spectral luminosity is also higher than that of the radio bursts detected from the Galactic magnetar SGR 1935 + 2154 during its outburst in April 2020, but it falls on the low-end of the currently measured luminosity distribution of extragalatic FRBs, further indicating the presence of a continuum of FRB luminosities. The temporal separation of the individual components has similarities to the quasiperiodic behavior seen in the microstructure of some pulsars. The known empirical relation between the microstructure quasiperiodicity timescale and the rotation period of pulsars possibly suggests a possible pulsar as the source of this FRB, with a rotation period of a few milliseconds.

Keywords: radio transient sources; radio bursts
No Evidence for Time Variation in Saturn's Internal Magnetic Field

The time variation of a planetary magnetic field can reveal important aspects of a planet's interior structure. Searching for time variation in planetary magnetic fields other than Earth has proved challenging owing to the small number of spacecraft missions flown to date, but such a detection may be possible given a sufficiently long baseline for comparison. Here we leverage 38 years of spacecraft magnetometer measurements to search for time variation in Saturn's internal magnetic field. To isolate the possible signal of time variation, we remove a contemporary high-resolution internal field model, derived from Cassini data, as well as a best-fitting external magnetodisk field model from each of four past mission data sets: Pioneer 11 (1979), Voyager 1 (1980), Voyager 2 (1981), and Cassini Saturn Orbit Insertion (2004). We then attempt to fit the resulting signal with an axisymmetric internal field model. Overall, we find no evidence of time variation on a multidecadal timescale. Our results lend support to the existence of a stably stratified layer in Saturn and have comparative planetology implications for Jupiter's interior structure and dynamics.

Keywords: saturn; jupiter; planetary interior; planetary magnetospheres; planetary science; magnetic fields; geomagnetic fields; magnetic anomalies
HaloFlow. I. Neural Inference of Halo Mass from Galaxy Photometry and Morphology

We present HaloFlow, a new machine-learning approach for inferring the mass of host dark matter halos, M h , from the photometry and morphology of galaxies (https://github.com/changhoonhahn/haloflow/). HaloFlow uses simulation-based inference with normalizing flows to conduct rigorous Bayesian inference. It is trained on state-of-the-art synthetic galaxy images from Bottrell et al. that are constructed from the IllustrisTNG hydrodynamic simulation and include realistic effects of the Hyper Suprime-Cam Subaru Strategy Program observations. We design HaloFlow to infer M h and stellar mass, M *, using grizy band magnitudes, morphological properties quantifying characteristic size, concentration and asymmetry, total measured satellite luminosity, and number of satellites. We demonstrate that HaloFlow infers accurate and unbiased posteriors of M h . Furthermore, we quantify the full information content in the photometric observations of galaxies in constraining M h . With magnitudes alone, we infer M h with and 0.182 dex for field and group galaxies. Including morphological properties significantly improves the precision of M h constraints, as does total satellite luminosity: and 0.132 dex. Compared to the standard approach using the stellar-to-halo mass relation, we improve M h constraints by ∼40%. In subsequent papers, we will validate and calibrate HaloFlow with galaxy–galaxy lensing measurements on real observational data.

Keywords: large-scale structure of the universe; cosmology; galaxy clusters; galaxy groups; neural networks; bayesian statistics
Extremely Inclined Orbit of the S-type Planet γ Cep Ab Induced by the Eccentric Kozai-Lidov Mechanism

γ Cep Ab is a typical S-type planet, which occupies a nearly perpendicular planetary orbit relative to the binary. Here, we use a Markov Chain Monte Carlo sampler to conduct a full N-body fitting and derive self-consistent orbital solutions for this hierarchical system. We then employ the eccentric Kozai-Lidov (EKL) mechanism to explain the extremely inclined orbit of the S-type planet γ Cep Ab. The EKL mechanism plays an essential part in our exploration of the significant oscillations of the mutual inclination i mut between the planet and the secondary star. We perform a qualitative analysis and use extensive numerical integrations to investigate the flip conditions and timescales of γ Cep Ab's orbit. When the planetary mass is 15 M Jup, the planet can reach i mut ~ 113° given the critical initial conditions of i mut < 60° and e 1 < 0.7. The timescale for the first orbital flip decreases with the increase of the perturbation Hamiltonian. The flipping orbits of γ Cep Ab are confirmed to have a large possibility of remaining stable, based on surfaces of section and the secular stability criterion. Furthermore, we extend the application of EKL to general S-type planetary systems with a 1/a 2 ≤ 0.1, where the most intense excitation of i mut occurs when a 1/a 2 = 0.1 and e 2 ~ 0.8, and the variation in planetary mass mainly affects the flip possibility where e 1 ≤ 0.3.

Keywords: exoplanet dynamics