adsabs/SciX_UAT_keywords huggingface dataset:
The Huge Magnetic Toroids in the Milky Way Halo

The magnetic fields in our Milky Way can be revealed by the distribution of Faraday rotation measures (RMs) of radio sources behind the Galaxy and of radio pulsars inside the Galaxy. Based on the antisymmetry of the Faraday sky in the inner Galaxy to the Galactic coordinates, the magnetic field toroids above and below the Galactic plane with reversed field directions exist in the Galactic halo and have been included in almost all models for the global magnetic structure in the Milky Way. However, the quantitative parameters—such as the field strength, the scale height, and the scale radius of the toroids—are hard to determine from observational data. It has long been argued that the RM antisymmetry could be dominated by the local contributions of the interstellar medium. Here, we get the local-discounted RM contributions from the RM sky and RMs of pulsars and get the first quantitative estimate of the sizes of the magnetic toroids in the Galactic halo. They are huge, starting from a Galactocentric radius of less than 2 kpc and extending to at least 15 kpc, without field direction reversals. Such magnetic toroids in the Galactic halo should naturally constrain the physical processes in galaxies.

Keywords: galaxy magnetic fields; interstellar medium
A Study of Variations of Galactic Cosmic-Ray Intensity Based on a Hybrid Data-processing Method

The low-energy cosmic-ray (CR) fluxes measured by space-borne instruments are generally considered to consist of gradually changing galactic CRs (GCRs) and short-lived solar energetic particles (SEPs). The SEP events cause sharp and ephemeral increases in the time profile of CR observations, with a higher occurrence rate in solar maximum. It is necessary to eliminate such spikes and obtain the pure GCR component while studying the modulation of GCRs in both short and long timescales. A hybrid data-processing method based on spike detection and time series analysis techniques is developed to remove the spikes and decompose the GCR data observed by the Interplanetary Monitoring Platform 8 into the long-term variation trend and the 27 day variation components. With the hybrid data-processing method, the 11 yr and 27 day variations in the intensity of low-energy GCRs can be studied systematically. Using the fitted trend component, the time lag in the solar modulation of low-energy GCRs is studied, and the results show that the time lag is both epoch and energy dependent. The obtained 27 day variation component is anticorrelated with the changes in solar wind velocity even during solar maximum. Implementing the running Fourier series fit procedure, the 27 day variation amplitude of the proton flux is computed. It is found that the yearly averaged values clearly show 11 and 22 yr variation cycles. In addition, the energy spectrum of the 27 day variation amplitude is softer in the A < 0 solar minimum than that in the A > 0 solar minimum.

Keywords: cosmic rays; solar activity; solar energetic particles
Discovery of a Brown Dwarf with Quasi-spherical Mass Loss

We report the serendipitous discovery of an elliptical shell of CO associated with the faint stellar object SSTc2d J163134.1-240060 as part of the "Ophiuchus Disk Survey Employing ALMA" (ODISEA), a project aiming to study the entire population of protoplanetary disks in the Ophiuchus Molecular Cloud from 230 GHz continuum emission and 12CO (J = 2-1), 13CO (J = 2-1) and C18CO (J = 2-1) lines readable in Band 6. Remarkably, we detect a bright 12CO elliptical shape emission of ~3″ × 4″ toward SSTc2d J163134.1-240060 without a 230 GHz continuum detection. Based on the observed near-IR spectrum taken with the Very Large Telescope (KMOS), the brightness of the source, its three-dimensional motion, and Galactic dynamic arguments, we conclude that the source is not a giant star in the distant background (>5-10 kpc) and is most likely to be a young brown dwarf in the Ophiuchus cloud, at a distance of just ~139 pc. This is the first report of quasi-spherical mass loss in a young brown dwarf. We suggest that the observed shell could be associated with a thermal pulse produced by the fusion of deuterium, which is not yet well understood, but for a substellar object is expected to occur during a short period of time at an age of a few Myr, in agreement with the ages of the objects in the region. Other more exotic scenarios, such as a merger with planetary companions, cannot be ruled out from the current observations.

Keywords: stellar wind bubbles; circumstellar clouds; stellar winds
PERISTOLE: Package That Generates Time Delay Plots Caused by Gravitational Lensing

We present PERISTOLE to study the various time delays associated with the pulsar rotation and other general relativistic aspects of binary pulsars. It is made available as an open-source python package which takes some parameters of the double pulsar system as input and outputs the rotational and latitudinal lensing delays along with the geometric and Shapiro delays that arise due to gravitational lensing. This package was intended to provide a way to quickly analyze, evaluate and study the differences between variations of the same systems and also to quantify the consequences that different parameters have over the system. Through this research note, we briefly describe the motivation behind PERISTOLE and showcase its capabilities using the only double pulsar system ever found, J0737-3039.

Keywords: astronomy software; binary pulsars; astroinformatics
A Search for Correlations between Turbulence and Star Formation in LITTLE THINGS Dwarf Irregular Galaxies

Turbulence has the potential for creating gas density enhancements that initiate cloud and star formation (SF), and it can be generated locally by SF. To study the connection between turbulence and SF, we looked for relationships between SF traced by FUV images, and gas turbulence traced by kinetic energy density (KED) and velocity dispersion (vdisp) in the LITTLE THINGS sample of nearby dIrr galaxies. We performed 2D cross-correlations between FUV and KED images, measured cross-correlations in annuli to produce correlation coefficients as a function of radius, and determined the cumulative distribution function of the cross-correlation value. We also plotted on a pixel-by-pixel basis the locally excess KED, vdisp, and H I mass surface density, ΣHI, as determined from the respective values with the radial profiles subtracted, versus the excess SF rate density ΣSFR, for all regions with positive excess ΣSFR. We found that ΣSFR and KED are poorly correlated. The excess KED associated with SF implies a ∼0.5% efficiency for supernova energy to pump local H I turbulence on the scale of the resolution here, which is a factor of ∼2 too small for all of the turbulence on a galactic scale. The excess vdisp in SF regions is also small, only ∼0.37 km s-1. The local excess in ΣHI corresponding to an excess in ΣSFR is consistent with a H I consumption time of ∼1.6 Gyr in the inner parts of the galaxies. The similarity between this timescale and the consumption time for CO implies that CO-dark molecular gas has comparable mass to H I in the inner disks.

Keywords: dwarf irregular galaxies
Overview and Validation of the Asteroseismic Modeling Portal v2.0

The launch of NASA's Kepler space telescope in 2009 revolutionized the quality and quantity of observational data available for asteroseismic analysis. While Kepler was able to detect solar-like oscillations in hundreds of main-sequence and subgiant stars, the Transiting Exoplanet Survey Satellite is now making similar observations for thousands of the brightest stars in the sky. The Asteroseismic Modeling Portal (AMP) is an automated and objective stellar model-fitting pipeline for asteroseismic data, which was originally developed to use models from the Aarhus Stellar Evolution Code. We briefly summarize an updated version of the AMP pipeline that uses Modules for Experiments in Stellar Astrophysics, and we present initial modeling results for the Sun and several solar analogs to validate the precision and accuracy of the inferred stellar properties.

Keywords: asteroseismology; open source software; stellar physics; computational methods
The Black Hole Mass of the z = 2.805 Multiply Imaged Quasar SDSS J2222+2745 from Velocity-resolved Time Lags of the C IV Emission Line

We present the first results of a 4.5 yr monitoring campaign of the three bright images of multiply imaged z = 2.805 quasar SDSS J2222+2745 using the Gemini North Multi-Object Spectrograph and the Nordic Optical Telescope. We take advantage of gravitational time delays to construct light curves surpassing 6 yr in duration in the observed frame and achieve an average spectroscopic cadence of 10 days during the 8 months of visibility per season. Using multiple secondary calibrators and advanced reduction techniques, we achieve percent-level spectrophotometric precision and carry out an unprecedented reverberation mapping analysis, measuring both integrated and velocity-resolved time lags for the C IV emission line. The full line lags the continuum by ${\tau }_{\mathrm{cen}}={36.5}_{-3.9}^{+2.9}$ rest-frame days. We combine our measurement with published C IV emission line lags and derive the rBLR - L relationship ${\mathrm{log}}_{10}(\tau /{\rm{d}}{\rm{a}}{\rm{y}})=(0.99\,\pm 0.07)+(0.48\pm 0.03){\mathrm{log}}_{10}[\lambda {L}_{\lambda }(1350\,{\rm{A}}{\rm{A}})/{10}^{44}\,{{\rm{e}}{\rm{r}}{\rm{g}}{\rm{s}}}^{-1}]$ with 0.30 ± 0.06 dex intrinsic scatter. The velocity-resolved lags are consistent with circular Keplerian orbits, with ${\tau }_{\mathrm{cen}}={86.2}_{-5.0}^{+4.5}$ , ${25}_{-15}^{+11}$ , and ${7.5}_{-3.5}^{+4.2}$ rest-frame days for the core, blue wing, and red wing, respectively. Using σline with the mean spectrum and assuming ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma })=0.52\pm 0.26$ , we derive ${\mathrm{log}}_{10}({M}_{\mathrm{BH}}/{M}_{\odot })=8.63\pm 0.27$ . Given the quality of the data, this system represents a unique benchmark for calibration of MBH estimators at high redshift. Future work will present dynamical modeling of the data to constrain the virial factor f and MBH.

Keywords: active galactic nuclei; strong gravitational lensing; reverberation mapping; supermassive black holes
Spectroscopic Studies of Type Ia Supernovae Using LSTM Neural Networks

We present a data-driven method based on long short-term memory (LSTM) neural networks to analyze spectral time series of Type Ia supernovae (SNe Ia). The data set includes 3091 spectra from 361 individual SNe Ia. The method allows for accurate reconstruction of the spectral sequence of an SN Ia based on a single observed spectrum around maximum light. The precision of the spectral reconstruction increases with more spectral time coverages, but the significant benefit of multiple epoch data at around optical maximum is only evident for observations separated by more than a week. The method shows great power in extracting the spectral information of SNe Ia and suggests that the most critical information of an SN Ia can be derived from a single spectrum around the optical maximum. The algorithm we have developed is important for the planning of spectroscopic follow-up observations of future SN surveys with the LSST/Rubin and WFIRST/Roman telescopes.

Keywords: supernovae; type ia supernovae
Thermonuclear Explosions and Accretion-induced Collapses of White Dwarfs in Active Galactic Nucleus Accretion Disks

White dwarfs (WDs) embedded in the gaseous disks of active galactic nuclei (AGNs) can rapidly accrete materials from these disks and grow in mass to reach, or even exceed, the Chandrasekhar limit. Binary WD (BWD) mergers are also believed to occur in AGN accretion disks. We study observational signatures from these events. We suggest that mass-accreting WDs and BWD mergers in AGN disks can lead to thermonuclear explosions that drive an ejecta shock breakout from the disk surface and power a slow-rising, relatively dim Type Ia supernova (SN). It is possible that such SNe Ia may be outshone by the emission of the AGN disk around a supermassive black hole (BH) with a mass of MSMBH ≳ 108 M⊙. In addition, accretion-induced collapses (AICs) of WDs in AGN disks may sometimes occur, which may form highly magnetized millisecond neutron stars (NSs). The subsequent spindown process of this nascent magnetar can deposit its rotational energy into the disk materials, resulting in a magnetar-driven shock breakout and a luminous magnetar-powered transient. We show that such an AIC event could power a rapidly evolving and luminous transient for a magnetic field of B ∼ 1015 G. The rising time and peak luminosity of the transient, powered by a magnetar with B ∼ 1014 G, are predicted to have similar properties to those of superluminous SNe. AIC events taking place in the inner parts of disks around relatively less massive supermassive BHs (MSMBH ≲ 108 M⊙) are more likely to power transients that are much brighter than the AGN disk emission, and hence easily identified.

Keywords: white dwarf stars; neutron stars; supernovae; active galactic nuclei; radiative transfer
WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5: The First Extreme T-type Subdwarfs?

We present the discoveries of WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5, two low-temperature (1200-1400 K), high proper motion T-type subdwarfs. Both objects were discovered via their high proper motion (>0"5 yr-1); WISEA J181006.18-101000.5 as part of the NEOWISE proper motion survey and WISEA J041451.67-585456.7 as part of the citizen science project Backyard Worlds; Planet 9. We have confirmed both as brown dwarfs with follow-up near-infrared spectroscopy. Their spectra and near-infrared colors are unique among known brown dwarfs, with some colors consistent with L-type brown dwarfs and other colors resembling those of the latest-type T dwarfs. While no forward model consistently reproduces the features seen in their near-infrared spectra, the closest matches suggest very low metallicities ([Fe/H] $\leqslant $ -1), making these objects likely the first examples of extreme subdwarfs of the T spectral class (esdT). WISEA J041451.67-585456.7 and WISEA J181006.18-101000.5 are found to be part of a small population of objects that occupy the "substellar transition zone," and have the lowest masses and effective temperatures of all objects in this group.

Keywords: t subdwarfs; brown dwarfs; subdwarf stars; t dwarfs
Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds. II. Validation of Theory with Hydrodynamic Simulations

In a companion paper, we develop a theory for the evolution of stellar wind-driven bubbles in dense, turbulent clouds. This theory proposes that turbulent mixing at a fractal bubble/shell interface leads to highly efficient cooling, in which the vast majority of the input wind energy is radiated away. This energy loss renders the majority of the bubble evolution momentum driven rather than energy driven, with expansion velocities and pressures orders of magnitude lower than in the classical Weaver et al. solution. In this paper, we validate our theory with three-dimensional, hydrodynamic simulations. We show that extreme cooling is not only possible, but is generic to star formation in turbulent clouds over more than three orders of magnitude in density. We quantify the few free parameters in our theory, and show that the momentum exceeds the wind input rate by only a factor ${\alpha }_{p}\sim 1.2\mbox{--}4$ . We verify that the bubble/cloud interface is a fractal with dimension $\sim 2.5\mbox{--}2.7$ . The measured turbulent amplitude ( ${v}_{t}\sim 200\mbox{--}400\,\ \mathrm{km}\,\ {{\rm{s}}}^{-1}$ ) in the hot gas near the interface is shown to be consistent with theoretical requirements for turbulent diffusion to efficiently mix and radiate away most of the wind energy. The fraction of energy remaining after cooling is only $1-{\rm{\Theta }}\sim 0.1\mbox{--}0.01$ , decreasing with time, explaining observations that indicate low hot-gas content and weak dynamical effects of stellar winds.

Keywords: star formation; stellar wind bubbles; stellar winds; molecular clouds; star clusters; young star clusters
Comprehensive Chemistry of HeH+ in the Early Universe

The recent detection of the helium hydride ion (HeH+) in the planetary nebula NGC 7027 has inspired studies revisiting the dominant processes for its formation and destruction. Because radiative association is the primary formation mechanism for the helium hydride ion at all redshifts, and many early universe chemistry models rely on accurate results for calculations of destruction rates, we explicitly computed rovibrationally distinguished partial cross sections and rate coefficients of helium hydride formation via radiative association, and modeled the abundance of HeH+ in the early universe using recently available rate coefficients for all relevant formation and destruction reactions. The rate coefficients for the radiative association formation reaction of HeH+ and radiative charge transfer in He+ + H collisions were obtained using two distinct methods. Our newly calculated rate coefficients along with other recently reported He chemistry reactions and updated cosmological parameters were incorporated into a new calculation of the abundance of HeH+ for redshifts between z = 10 and 4000. We find that the abundance of the helium hydride ion is at least three orders of magnitude larger than previous predictions for redshifts near z = 20. Rovibrationally distinguished radiative association rate coefficients are given as a function of temperature, and the significance of stimulated radiative association for redshifts z > 400 is also shown. * Released on Month Date Year.

Keywords: early universe; interstellar abundances; molecule formation
AGN STORM 2. II. Ultraviolet Observations of Mrk 817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope

We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk 817 using 165 spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our ultraviolet observations are accompanied by X-ray, optical, and near-infrared observations as part of the AGN Space Telescope and Optical Reverberation Mapping Program 2 (AGN STORM 2). Using the cross-correlation lag analysis method, we find significant correlated variations in the continuum and emission-line light curves. We measure rest-frame delayed responses between the far-ultraviolet continuum at 1180 Å and Lyα λ1215 Å ( ${10.4}_{-1.4}^{+1.6}$ days), N V λ1240 Å ( ${15.5}_{-4.8}^{+1.0}$ days), Si IV + ]O IV λ1397 Å ( ${8.2}_{-1.4}^{+1.4}$ days), C IV λ1549 Å ( ${11.8}_{-2.8}^{+3.0}$ days), and He II λ1640 Å ( ${9.0}_{-1.9}^{+4.5}$ days) using segments of the emission-line profile that are unaffected by absorption and blending, which results in sampling different velocity ranges for each line. However, we find that the emission-line responses to continuum variations are more complex than a simple smoothed, shifted, and scaled version of the continuum light curve. We also measure velocity-resolved lags for the Lyα and C IV emission lines. The lag profile in the blue wing of Lyα is consistent with virial motion, with longer lags dominating at lower velocities, and shorter lags at higher velocities. The C IV lag profile shows the signature of a thick rotating disk, with the shortest lags in the wings, local peaks at ±1500 km s-1, and a local minimum at the line center. The other emission lines are dominated by broad absorption lines and blending with adjacent emission lines. These require detailed models, and will be presented in future work. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program GO-16196."

Keywords: active galactic nuclei; reverberation mapping; active galaxies; seyfert galaxies
Effect of Extinction on Quasar Luminosity Distances Determined from UV and X-Ray Flux Measurements

In Khadka et al., a sample of X-ray-detected reverberation-mapped quasars was presented and applied for the comparison of cosmological constraints inferred using two well-established relations in active galactic nuclei—the X-ray/UV luminosity (L X –L UV) relation and the broad-line region radius–luminosity (R–L) relation. L X –L UV and R–L luminosity distances to the same quasars exhibit a distribution of their differences that is generally asymmetric and positively shifted for the six cosmological models we consider. We demonstrate that this behavior can be interpreted qualitatively as arising as a result of the dust extinction of UV/X-ray quasar emission. We show that the extinction always contributes to the nonzero difference between L X –L UV-based and R–L-based luminosity distances and we derive a linear relationship between the X-ray/UV color index E X‑UV and the luminosity-distance difference, which also depends on the value of the L X –L UV relation slope. Taking into account the median and the peak values of the luminosity-distance difference distributions, the average X-ray/UV color index falls in the range of ${\overline{E}}_{X-\mathrm{UV}}=0.03\mbox{--}0.28$ mag for the current sample of 58 sources. This amount of extinction is typical for the majority of quasars and can be attributed to the circumnuclear and interstellar media of host galaxies. After applying the standard hard X-ray and far-UV extinction cuts, heavily extincted sources are removed but overall the shift toward positive values persists. The effect of extinction on luminosity distances is more pronounced for the L X –L UV relation since the extinction of UV and X-ray emissions both contribute.

Keywords: cosmology; cosmological parameters; observational cosmology; active galaxies; quasars; interstellar dust extinction
On the (Lack of) Evolution of the Stellar Mass Function of Massive Galaxies from z = 1.5 to 0.4

We study the evolution in the number density of galaxies at the highest stellar masses over the past ≈9 Gyr (0.4< z< 1.5) using the Spitzer/HETDEX Exploratory Large-Area Survey (SHELA). SHELA includes complete imaging in eight photometric bands spanning 0.3-4.5 μm over 17.5 deg2 within the SDSS Stripe 82 field. The size of SHELA produces the lowest counting uncertainties and cosmic variance yet for massive galaxies at z ∼ 1.0. We study the evolution in the intrinsic stellar mass function (SMF) for galaxies with log(M*/M⊙) > 10.3 using a forward-modeling method that takes into full account the statistical and systematic uncertainties on stellar mass. From z = 0.4 to 1.5, the evolution in the massive end of the intrinsic SMF shows minimal change in its shape: the characteristic mass (M*) evolves by less than 0.1 dex (±0.05 dex); furthermore, the number density of galaxies with log M*/M⊙ > 11 stays roughly constant at log (n/Mpc-3)≃ -3.4 (±0.05) from z = 1 to z = 0.4, consistent with no evolution, then declines to log n/Mpc-3 = -3.7 (±0.05) at z = 1.5. We discuss the uncertainties in the derived SMF, which are dominated by assumptions in the star formation history and details of stellar population synthesis models for stellar mass estimations. We also study the evolution in the SMF for samples of star-forming and quiescent galaxies selected by their specific star formation rate. For quiescent galaxies, the data are consistent with no (or slight) evolution (≲0.1 dex) in either the characteristic mass or number density from z ∼ 1.5 to the present even after accounting for the systematic uncertainty and the random error in the stellar mass measurement. The lack of number density evolution in the quiescent massive galaxy population means that any mass growth (presumably through "dry" mergers) must balance the rate of stellar mass losses owing to processes of late-stage stellar evolution and the formation of newly quiescent galaxies from the star-forming population. We provide an upper limit on this mass growth from z = 1.0 to 0.4 of ΔM*/M* = 45% (I.e., ≃0.16 dex) for quiescent galaxies more massive than 1011 M⊙.

Keywords: galaxy abundances; galaxy evolution