adsabs/SciX_UAT_keywords huggingface dataset:
Shadows in the Dark: Low-surface-brightness Galaxies Discovered in the Dark Energy Survey

We present a catalog of 23,790 extended low-surface-brightness galaxies (LSBGs) identified in $\sim 5000\,{\deg }^{2}$ from the first three years of imaging data from the Dark Energy Survey (DES). Based on a single-component Sérsic model fit, we define extended LSBGs as galaxies with g-band effective radii ${R}_{\mathrm{eff}}(g)\gt 2\buildrel{\prime\prime}\over{.} 5$ and mean surface brightness ${\bar{\mu }}_{\mathrm{eff}}(g)\gt 24.2\,\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ . We find that the distribution of LSBGs is strongly bimodal in (g - r) versus (g - i) color space. We divide our sample into red (g - i ≥ 0.60) and blue (g - i < 0.60) galaxies and study the properties of the two populations. Redder LSBGs are more clustered than their blue counterparts and are correlated with the distribution of nearby (z < 0.10) bright galaxies. Red LSBGs constitute ∼33% of our LSBG sample, and $\sim 30 \% $ of these are located within 1° of low-redshift galaxy groups and clusters (compared to ∼8% of the blue LSBGs). For nine of the most prominent galaxy groups and clusters, we calculate the physical properties of associated LSBGs assuming a redshift derived from the host system. In these systems, we identify 41 objects that can be classified as ultradiffuse galaxies, defined as LSBGs with projected physical effective radii ${R}_{\mathrm{eff}}\gt 1.5\,\mathrm{kpc}$ and central surface brightness ${\mu }_{0}(g)\gt 24.0\,\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ . The wide-area sample of LSBGs in DES can be used to test the role of environment on models of LSBG formation and evolution.

Keywords: sky surveys; low surface brightness galaxies
Evolutionary Period Changes for 52 Cataclysmic Variables, and the Failure for the Most-fundamental Prediction of the Magnetic Braking Model

The evolution of cataclysmic variables (CVs) is driven by period changes ( $\dot{P}$ ), for which the long-venerable consensus is the magnetic braking model (MBM). The MBM has its only distinctive assumption being a power-law "recipe" describing the angular momentum loss (AML) in the binary, producing a single unique evolutionary track with $\dot{P}$ as a function of the orbital period. This required prediction can be used to test the most-fundamental assumption of MBM, but it has never been tested previously. In this paper, I collect $\dot{P}$ measures for 52 CVs of all types. First, 44% of the CVs have positive $\dot{P}$ , with such being impossible in MBM. Second, even among the CVs with negative $\dot{P}$ , their $\dot{P}$ measures are always more negative than required by MBM, with an average deviation of 110×. Third, three CVs have large chaotic variations in $\dot{P}$ that are impossible for MBM, proving that some unknown mechanism exists and is operating that dominates for these systems. Fourth, the MBM does not account for the long-term effects on evolution arising from the large sudden period decreases seen across many nova events, with this unaccounted effect dominating for the majority of nova systems and changing the sign of the overall evolutionary $\dot{P}$ . Fifth, three recurrent novae are observed to suddenly change $\dot{P}$ by an order of magnitude across a nova event, with this being impossible in the MBM. In all, the required MBM $\dot{P}$ predictions all fail for my 52 CVs, usually by orders of magnitude, so the MBM AML-recipe is wrong by orders of magnitude.

Keywords: classical novae; recurrent novae; cataclysmic variable stars
Multiwavelength Observations of the Obscuring Wind in the Radio-quiet Quasar MR 2251-178

Obscuring winds driven away from active supermassive black holes are rarely seen due to their transient nature. They have been observed with multiwavelength observations in a few Seyfert 1 galaxies and one broad absorption line radio-quiet quasar so far. An X-ray obscuration event in MR 2251-178 was caught in late-2020, which triggered multiwavelength (near-IR (NIR) to X-ray) observations targeting this radio-quiet quasar. In the X-ray band, the obscurer leads to a flux drop in the soft X-ray band from late-2020 to early-2021. X-ray obscuration events might have a quasi-period of two decades considering earlier events in 1980 and 1996. In the UV band, a forest of weak blueshifted absorption features emerged in the blue wing of Lyα λ1216 in late-2020. Our XMM-Newton, NuSTAR, and Hubble Space Telescope/COS observations are obtained simultaneously; hence, the transient X-ray obscuration event is expected to account for the UV outflow, although they are not necessarily caused by the same part of the wind. Both blueshifted and redshifted absorption features were found for He I λ10830, but no previous NIR spectra are available for comparison. The X-ray observational features of MR 2251-178 shared similarities with some other type 1 active galactic nuclei (AGNs) with obscuring wind. However, observational features in the UV to NIR bands are distinctly different from those seen in other AGN with obscuring winds. A general understanding of the observational variety and the nature of obscuring wind is still lacking.

Keywords: astrophysical black holes; x-ray quasars; quasar absorption line spectroscopy; high resolution spectroscopy; active galactic nuclei
A Coscaling Grid for Athena++

We present a coscaling-grid formalism and its implementation in the magnetohydrodynamics code Athena++. The formalism relies on flow symmetries in astrophysical problems involving expansion, contraction, and center-of-mass motion. The grid is evolved at the same time order as the fluid variables. The user specifies grid evolution laws, which can be independent of the fluid motion. Applying our implementation to standard hydrodynamic test cases leads to improved results and higher efficiency, compared to the fixed-grid solutions.

Keywords: computational methods; hydrodynamical simulations; astronomical simulations
Inferring Vector Magnetic Fields from Stokes Profiles of GST/NIRIS Using a Convolutional Neural Network

We propose a new machine-learning approach to Stokes inversion based on a convolutional neural network (CNN) and the Milne-Eddington (ME) method. The Stokes measurements used in this study were taken by the Near InfraRed Imaging Spectropolarimeter (NIRIS) on the 1.6 m Goode Solar Telescope (GST) at the Big Bear Solar Observatory. By learning the latent patterns in the training data prepared by the physics-based ME tool, the proposed CNN method is able to infer vector magnetic fields from the Stokes profiles of GST/NIRIS. Experimental results show that our CNN method produces smoother and cleaner magnetic maps than the widely used ME method. Furthermore, the CNN method is four to six times faster than the ME method and able to produce vector magnetic fields in nearly real time, which is essential to space weather forecasting. Specifically, it takes ∼50 s for the CNN method to process an image of 720 × 720 pixels comprising Stokes profiles of GST/NIRIS. Finally, the CNN-inferred results are highly correlated to the ME-calculated results and closer to the ME's results with the Pearson product-moment correlation coefficient (PPMCC) being closer to 1, on average, than those from other machine-learning algorithms, such as multiple support vector regression and multilayer perceptrons (MLP). In particular, the CNN method outperforms the current best machine-learning method (MLP) by 2.6%, on average, in PPMCC according to our experimental study. Thus, the proposed physics-assisted deep learning-based CNN tool can be considered as an alternative, efficient method for Stokes inversion for high-resolution polarimetric observations obtained by GST/NIRIS.

Keywords: solar magnetic fields; computational methods; convolutional neural networks
Direct Measurements of Stellar Masses with the Habitable World Observatory

Background stars within ~1″ of a nearby massive object will have their centroids shift by about 1 mas due to microlensing. This provides mass measurements of stellar mass objects in the solar neighborhood. Habitable Worlds Observatory (HWO) targets toward the Galactic Bulge will have a sufficient density of background stars that HWO will be able to measure their masses independently of stellar evolutionary models, which will allow more accurate habitable histories of their exoplanets to be evaluated. This opportunity is maximized for designs of HWO with very high contrasts (Δmag ≳25) and the capability for precise relative astrometry with respect to the target star. HWO can apply this technique to any nearby stellar mass object in the direction of the Galactic Bulge, enhancing its science case and that of precursor missions like Roman.

Keywords: stellar masses; astrometric microlensing effect; gravitational microlensing; microlensing optical depth; coronagraphic imaging
Systematic Difference between Ionized and Molecular Gas Velocity Dispersions in z ∼ 1-2 Disks and Local Analogs

We compare the molecular and ionized gas velocity dispersions of nine nearby turbulent disks, analogs to high-redshift galaxies, from the DYNAMO sample using new Atacama Large Millimeter/submillimeter Array and GMOS/Gemini observations. We combine our sample with 12 galaxies at z ∼ 0.5-2.5 from the literature. We find that the resolved velocity dispersion is systematically lower by a factor 2.45 ± 0.38 for the molecular gas compared to the ionized gas, after correcting for thermal broadening. This offset is constant within the galaxy disks and indicates the coexistence of a thin molecular gas disk and a thick ionized one. This result has a direct impact on the Toomre Q and pressure derived in galaxies. We obtain pressures ∼0.22 dex lower on average when using the molecular gas velocity dispersion, σ0,mol. We find that σ0,mol increases with gas fraction and star formation rate. We also obtain an increase with redshift and show that the EAGLE and FIRE simulations overall overestimate σ0,mol at high redshift. Our results suggest that efforts to compare the kinematics of gas using ionized gas as a proxy for the total gas may overestimate the velocity dispersion by a significant amount in galaxies at the peak of cosmic star formation. When using the molecular gas as a tracer, our sample is not consistent with predictions from star formation models with constant efficiency, even when including transport as a source of turbulence. Feedback models with variable star formation efficiency, ɛff, and/or feedback efficiency, p*/m*, better predict our observations.

Keywords: extragalactic astronomy; high-redshift galaxies; galaxy kinematics; star formation; galaxy evolution; stellar feedback
The Galactic Interstellar Object Population: A Framework for Prediction and Inference

The Milky Way is thought to host a huge population of interstellar objects (ISOs), numbering approximately 1015 pc-3 around the Sun, which are formed and shaped by a diverse set of processes ranging from planet formation to Galactic dynamics. We define a novel framework, first to predict the properties of this Galactic ISO population by combining models of processes across planetary and Galactic scales, and second to make inferences about the processes being modeled, by comparing the predicted population to what is observed. We predict the spatial and compositional distribution of the Galaxy's population of ISOs by modeling the Galactic stellar population with data from the APOGEE survey and combining this with a protoplanetary disk chemistry model. Selecting the ISO water mass fraction as an example observable quantity, we evaluate its distribution both at the position of the Sun and averaged over the Galactic disk; our prediction for the solar neighborhood is compatible with the inferred water mass fraction of 2I/Borisov. We show that the well-studied Galactic stellar metallicity gradient has a corresponding ISO compositional gradient. We also demonstrate the inference part of the framework by using the current observed ISO composition distribution to constrain the parent star metallicity dependence of the ISO production rate. This constraint, and other inferences made with this framework, will improve dramatically as the Vera C. Rubin Observatory Legacy Survey of Space and Time progresses and more ISOs are observed. Finally, we explore generalizations of this framework to other Galactic populations, such as that of exoplanets.

Keywords: interstellar objects; small solar system bodies; milky way evolution
Genesis and Coronal-jet-generating Eruption of a Solar Minifilament Captured by IRIS Slit-raster Spectra

We present the first Mg II slit-raster spectra from the Interface Region Imaging Spectrograph (IRIS) that fully capture the genesis and coronal-jet-generating eruption of a central-disk solar minifilament. The minifilament arose in a negative-magnetic-polarity coronal hole. The Mg II spectroheliograms verify that the minifilament plasma temperature is chromospheric. The Mg II spectra show that the erupting minifilament's plasma has blueshifted upflow in the onset of the jet spire and simultaneous redshifted downflow at the location of the compact jet bright point (JBP). From the Mg II spectra together with Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and SDO/Helioseismic and Magnetic Imager (HMI) magnetograms, we find: (i) the minifilament forms above a flux-cancelation neutral line at an edge of a negative-polarity network flux clump; (ii) during the onset of the minifilament's fast eruption and jet spire, the JBP begins brightening over the flux-cancelation neutral line. From IRIS2 inversion of the Mg II spectra, the JBP's Mg II bright plasma has electron density, temperature, and downward (redshift) Doppler speed of 1012 cm-3, 6000 K, and 10 km s-1, respectively, and the growing spire shows clockwise spin. We speculate: (i) during the slow rise of the erupting minifilament-carrying a twisted flux rope, the top of the erupting flux-rope loop, by writhing, makes its field direction opposite to that of the encountered ambient far-reaching field; (ii) the erupting kink then can reconnect with the far-reaching field to create the spire and reconnect internally to create the JBP. We conclude that this coronal jet is normal in that magnetic flux cancelation builds a minifilament-carrying twisted flux rope and triggers the JBP-generating and jet-spire-generating eruption of the flux rope.

Keywords: solar magnetic fields; solar coronal holes; solar ultraviolet emission; solar magnetic reconnection; quiet solar chromosphere; spectroscopy; jets; solar corona
The Mass Fractionation of Helium in the Escaping Atmosphere of HD 209458b

The absorption signals of metastable He in HD 209458b and several other exoplanets can be explained via an escaping atmosphere model with a subsolar He/H ratio. The low abundance of helium can be a result of planet formation if there is a small amount of helium in their primordial atmosphere. However, another possibility is that the low He/H ratio is caused by the process of mass fractionation of helium in the atmosphere. In order to investigate the effect of fractionation in the hydrogen-helium atmosphere, we developed a self-consistent multi-fluid 1D hydrodynamic model based on the well-known open-source MHD code PLUTO. Our simulations show that a lower He/H ratio can be produced spontaneously in the multi-fluid model. We further modeled the transmission spectra of He 10830 lines for HD 209458b in a broad parameter space. The transmission spectrum of the observation can be fitted in the condition of 1.80 times the X-ray and extreme-ultraviolet flux of the quiet Sun. Meanwhile, the ratio of the escaping flux of helium to hydrogen, F He/F H, is 0.039. Our results indicate that the mass fractionation of helium to hydrogen can naturally interpret the low He/H ratio required by the observation. Thus, in the escaping atmosphere of HD 209458b, decreasing the abundance of helium in the atmosphere is not needed even if its He abundance is similar to that of the Sun. The simulation presented in this work hints that in the escaping atmosphere, mass fractionation can also occur on other exoplanets, which needs to be explored further. *Revised Manuscript on 2022 June 7

Keywords: exoplanet atmospheres; hydrodynamical simulations; radiative transfer simulations
Evidence of High-energy Neutrinos from SN1987A by Kamiokande-II and IMB

High-energy neutrinos from SN1987A were searched for using upward-going muons recorded by the Kamiokande-II experiment and the IMB experiment. Between 1987 August 11 and October 20, and from an angular window of 10° radius, two upward-going muon events were recorded by Kamiokande-II, and also two events were recorded by IMB. The probability that these upward-going muons were explained by a chance coincidence of atmospheric neutrinos was calculated to be 0.27%. This shows possible evidence of high-energy neutrinos from SN1987A.

Keywords: neutrino astronomy
Studying Magnetic Reconnection with Synchrotron Polarization Statistics

Magnetic reconnection is a fundamental process for releasing magnetic energy in space physics and astrophysics. At present, the usual way to investigate the reconnection process is through analytical studies or first-principle numerical simulations. This paper is the first to understand the turbulent magnetic reconnection process by exploring the nature of magnetic turbulence. From the perspective of radio synchrotron polarization statistics, we study how to recover the properties of the turbulent magnetic field by considering the line of sight along different directions of the reconnection layer. We find that polarization intensity statistics can reveal the spectral properties of reconnection turbulence. This work opens up a new way of understanding turbulent magnetic reconnection.

Keywords: magnetohydrodynamics; interplanetary turbulence; interstellar medium; computational methods; magnetohydrodynamical simulations
The Mars Orbiter for Resources, Ices, and Environments (MORIE) Science Goals and Instrument Trades in Radar, Imaging, and Spectroscopy

The Mars Orbiter for Resources, Ices, and Environments (MORIE) was selected as one of NASA's 2019 Planetary Mission Concept Studies. The mission builds upon recent discoveries and current knowledge gaps linked to two primary scientific questions: (1) when did elements of the cryosphere form and how are ice deposits linked to current, recent, and ancient climate, and (2) how does the crust record the evolution of surface environments and their transition through time? Addressing these questions has emerged in numerous recent reports as a high priority in investigating the evolution of Mars as a habitable world. A subsidiary goal of the mission concept is to provide information relevant to the eventual human exploration of Mars, specifically helping to locate and quantify near-surface water ice and hydrated mineral resources. The proposed instrument suite includes polarimetric synthetic aperture radar imaging, radar sounding, high-resolution visible and infrared imaging, both short-wave and thermal-infrared spectroscopy, and multichannel wide-angle imaging. MORIE would provide novel measurements of Mars expected to lead to significant new discoveries by the first radar imaging from orbit, radar sounding directly over the poles, and mineral mapping at spatial scales that will unravel geologic sequence stratigraphy through time. The final report of the mission concept provides details on the spacecraft, orbital design, technological maturity, results from systems-level integration studies, and costs. This article is intended to expand upon the science motivation for the mission, the measurement goals and objectives, and the instrument trade space that was examined in detail during the concept study.

Keywords: spectroscopy; radar astronomy; mars; space vehicle instruments
The Binary Black Hole Spin Distribution Likely Broadens with Redshift

The population-level distributions of the masses, spins, and redshifts of binary black holes (BBHs) observed using gravitational waves can shed light on how these systems form and evolve. Because of the complex astrophysical processes shaping the inferred BBH population, models allowing for correlations among these parameters will be necessary to fully characterize these sources. We hierarchically analyze the BBH population detected by LIGO and Virgo with a model allowing for correlations between the effective aligned spin and the primary mass and redshift. We find that the width of the effective spin distribution grows with redshift at 98.6% credibility. We determine this trend to be robust under the application of several alternative models and additionally verify that such a correlation is unlikely to be spuriously introduced using a simulated population. We discuss the possibility that this correlation could be due to a change in the natal black hole spin distribution with redshift.

Keywords: astrophysical black holes; gravitational wave astronomy; gravitational wave sources
A Dynamical Mass of 70 ± 5 MJup for Gliese 229B, the First T Dwarf

We combine Keck/HIRES radial velocities, imaging with HiCIAO/Subaru and the Hubble Space Telescope, and absolute astrometry from Hipparcos and Gaia to measure a dynamical mass of 70 ± 5 ${M}_{\mathrm{Jup}}$ for the brown dwarf companion to Gl 229. Gl 229B was the first imaged brown dwarf to show clear signs of methane in its atmosphere. Cooling models have been used to estimate a mass in the range of 20-55 ${M}_{\mathrm{Jup}}$ , much lower than our measured value. We argue that our high dynamical mass is unlikely to be due to perturbations from additional unseen companions or to Gl 229B itself being a binary, and we find no evidence of a previously claimed radial velocity planet around Gl 229A. Future Gaia data releases will confirm the reliability of the absolute astrometry, though the data pass all quality checks in both Hipparcos and Gaia. Our dynamical mass implies a very old age for Gl 229, in some tension with kinematic and activity age indicators, and/or shortcomings in brown dwarf cooling models. Gl 229B joins a small but growing list of T dwarfs with masses approaching the minimum mass for core hydrogen ignition.

Keywords: brown dwarfs; t subdwarfs; celestial mechanics
Energy Injection Driven by Precessing Jets in Gamma-Ray Burst Afterglows

Jet precession is considered to universally exist in different-scale astronomical phenomena, including gamma-ray bursts (GRBs). For the long-lived GRB central engine, the relativistic precessing jets will periodically inject kinetic energy into the external shocks, then significantly modulate the shapes of the light curves (LCs) in GRB afterglows. In this paper, we adopt the standard external shock model to investigate the effects of jet precession on GRB X-ray afterglows in cases with different parameters, i.e., the steady or time-dependent jet powers, precession periods, precession angles, and viewing angles. In the case where the jet powers are in steady or slow decay and the jet can sweep across the line of sight, shallow decay (or plateau) segments should appear; otherwise, a giant bump will emerge in the GRB afterglow LCs. We show that jet precession is a new plausible mechanism of the energy injection in GRBs. Moreover, some observed X-ray transients without GRB associations might be powered by the precessing jets.

Keywords: gamma-ray bursts; shocks; relativistic jets