adsabs/SciX_UAT_keywords huggingface dataset:
A High Spatial and Spectral Resolution Study of Jupiter's Mid-infrared Auroral Emissions and Their Response to a Solar Wind Compression

We present mid-infrared spectroscopy of Jupiter's mid-to-high latitudes using the Gemini-North/Texas Echelon Cross Echelle Spectrograph on 2017 March 17-19. These observations capture Jupiter's hydrocarbon auroral emissions before, during, and after the arrival of a solar wind compression on March 18, which highlights the coupling between the polar stratosphere and external space environment. In comparing observations on March 17 and 19, we observe a brightening of the CH4, C2H2, and C2H4 emission in regions spatially coincident with the northern duskside main auroral emission (MAE). In inverting the spectra to derive atmospheric information, we determine that the duskside brightening results from upper stratospheric (p < 0.1 mbar/z > 200 km) heating (e.g., ΔT = 9.1 ± 2.1 K at 9 μbar at 67.°5N, 162.°5W) with negligible heating at deeper pressures. Our interpretation is that the arrival of the solar wind enhancement drove magnetospheric dynamics through compression and/or viscous interactions on the flank. These dynamics accelerated currents and/or generated higher Poynting fluxes, which ultimately warmed the atmosphere through Joule heating and ion-neutral collisions. Poleward of the southern MAE, temperature retrievals demonstrate that auroral-related heating penetrates as deep as the 10 mbar level, in contrast to poleward of the northern MAE, where heating is only observed as deep as ~3 mbar. We suggest that this results from the south having higher Pedersen conductivities and therefore stronger currents and acceleration of the neutrals, as well as the poleward heating overlapping with the apex of Jupiter's circulation, thereby inhibiting efficient horizontal mixing/advection.

Keywords: aurorae; planetary magnetospheres; infrared astronomy; high resolution spectroscopy; aeronomy; jupiter; planetary atmospheres; planetary polar regions
Galaxy Spin Transition Driven by the Misalignments between the Protogalaxy Inertia and Initial Tidal Tensors

A numerical detection of the τ-driven transition of galaxy spins is presented, where τ is the degree of misalignment between the initial tidal field and protogalaxy inertia tensors. Analyzing the data from the IllustrisTNG300-1 simulations, we first measure the values of τ at the protogalactic sites found by tracing the constituents of the galactic halos in the mass range of $10.5\leqslant \mathrm{log}\left[{M}_{h}/({h}^{-1}{M}_{\odot })\right]\leqslant 13$ back to the initial stage, z i = 127. The probability density functions of τ are shown to be well modeled by the Γ-distributions, whose shape and scale parameters turn out to have universal values on a certain critical scale. Then, we investigate how the strength and tendency of the galaxy spin alignments with the principal axes of the local tidal fields depend on the initial condition, τ. It is found that on a scale lower than the critical one, the galaxy spin transition occurs at two different thresholds from the major to intermediate and from the intermediate to minor principal axes of the local tidal fields, respectively. Noting that the τ-dependent spin transition supersedes the strength of the previously found mass-dependent, morphology-dependent, and radius-dependent counterparts, we suggest that τ should be the key driver of all types of galaxy spin transitions and that the present galaxy spins are indeed excellent fossil records of their origin.

Keywords: cosmology; large-scale structure of the universe
Self-consistent Atmosphere Representation and Interaction in Photon Monte Carlo Simulations

We present a self-consistent representation of the atmosphere and implement the interactions of light with the atmosphere using a photon Monte Carlo approach. We compile global climate distributions based on historical data, self-consistent vertical profiles of thermodynamic quantities, spatial models of cloud variation and cover, and global distributions of four kinds of aerosols. We then implement refraction, Rayleigh scattering, molecular interactions, and Tyndall–Mie scattering to all photons emitted from astronomical sources and various background components using physics first principles. This results in emergent image properties that include: differential astrometry and elliptical point spread functions (PSFs) predicted completely to the horizon, arcminute-scale spatial-dependent photometry variations at 20 mmag for short exposures, excess background spatial variations at 0.2% due to the atmosphere, and a PSF wing due to water droplets. We use a common atmosphere representation framework to self-consistently model all phenomena by simulating individual photons. We reproduce the well-known correlations in image characteristics: correlations in altitude with absolute photometry (overall transmission) and relative photometry (spectrally dependent transmission), anticorrelations of altitude with differential astrometry (nonideal astrometric patterns) and background levels, and an anticorrelation in absolute photometry with cloud depth. However, we also find further subtle correlations including an anticorrelation of temperature with background and differential astrometry, a correlation of temperature with absolute and relative photometry, an anticorrelation of absolute photometry with humidity, a correlation of humidity with lunar background, a significant correlation of PSF wing with cloud depth, an anticorrelation of background with cloud depth, and a correlation of lunar background with cloud depth.

Keywords: earth atmosphere; astronomical instrumentation; astronomical simulations
Applying Random Forest Classification to Ultracool Dwarf Discovery in Deep Surveys. I. Color Classification with SDSS, UKIDSS, and WISE Photometry

In this first of two studies, we apply a random forest model to classify ultracool dwarfs from broadband color information. Using the Skrzypek et al. ultracool dwarf sample and a set of background sources, we trained a random forest classifier based on 28 colors derived from optical and infrared photometry from SDSS, UKIDSS, and WISE. Our model achieves 99.7% accuracy in segregating L- and T-type UCDs from background sources, and 97% accuracy in separating spectral subgroups. A separate random forest regressor model achieved a spectral classification precision of 1.3 subtypes. We applied these models to a 12.6 deg2 region with overlapping SDSS, UKIDSS, and WISE coverage and identified 35 UCD candidates, five of which are previously reported, of which four are photometrically or spectroscopically classified UCDs. Our random forest model can be applied to multiple surveys to greatly expand the known census of UCDs.

Keywords: brown dwarfs; l dwarfs; t dwarfs; stellar classification; surveys; random forests; classification; low mass stars
Investigation of Galactic Supernova Remnants and their Environment in 26.°6 < l < 30.°6, ∣b∣ ≤ 1.°25 Using Radio Surveys

The problem of missing Galactic supernova remnants (SNRs) refers to the issue that the currently known Galactic SNRs are significantly incomplete compared to the theoretical prediction. To expand the sample of Galactic SNRs, we use GLEAM and THOR+VGPS data across four wave bands ranging from 118 to 1420 MHz to drive a spectral index map covering the region within 26.°6 < l < 30.°6, ∣b∣ ≤ 1.°25, where numerous SNR candidates were recently found. By using the spectral index map of the sky region and detailed analysis of the spectral indices of individual sources, we confirmed four SNR candidates, namely G26.75+0.73, G27.06+0.04, G28.36+0.21, and G28.78‑0.44, as SNRs. Additionally, we discovered an expanding molecular superbubble located in this region, discussed pulsars associated with SNR candidates, and discovered a long Hα filament that spatially overlaps with the candidate G29.38+0.10. We suggest that the problem of missing Galactic SNRs not only arises from observation limitations, but also could be due to the low-density environments of some SNRs, and the different supernova explosion properties.

Keywords: supernova remnants; radio continuum emission; superbubbles
Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events

The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than ${M}_{V}=-19$ mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than -20.5 mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized 56Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg. * This paper includes data gathered with the 1 m Swope and 2.5 m du Pont telescopes at Las Campanas Observatory, Chile, and the Nordic Optical Telescope at the Observatorio del Roque de los Muchachos, La Palma, Spain.

Keywords: type ia supernovae; asymptotic giant branch stars; stellar winds
Chandra Monitoring of the J1809-1917 Pulsar Wind Nebula and Its Field

PSR J1809-1917 is a young (τ = 51 kyr) and energetic ( $\dot{E}=1.8\times {10}^{36}$ erg s-1) radio pulsar powering an X-ray pulsar wind nebula (PWN) that exhibits morphological variability. We report on the results of a new monitoring campaign by the Chandra X-ray Observatory (Chandra), carried out across six epochs with a ∼7 week cadence. The compact nebula can be interpreted as a jet-dominated outflow along the pulsar's spin axis. Its variability can be the result of Doppler boosting in the kinked jet, whose shape changes with time (akin to the Vela pulsar jet). The deep X-ray image, composed of 405 ks of new and 131 ks of archival Chandra data, reveals an arcminute-scale extended nebula (EN) whose axis of symmetry aligns with both the axis of the compact nebula and the direction toward the peak of the nearby TeV source HESS J1809-193. The EN's morphology and extent suggest that the pulsar is likely moving through the ambient medium at a transonic velocity. We also resolved a faint 7' long nonthermal collimated structure protruding from the PWN. It is possibly another instance of a "misaligned outflow" (also known as a "kinetic jet") produced by high-energy particles escaping the PWN's confinement and tracing the interstellar magnetic field lines. Finally, taking advantage of the 536 ks exposure, we analyzed the point sources in the J1809 field and classified them using multiwavelength data. None of the classified sources in the field can reasonably be expected to produce the extended TeV flux in the region, suggesting that PSR J1809-1917 is indeed the counterpart to HESS/eHWC J1809-193.

Keywords: pulsars; rotation powered pulsars; radio pulsars; neutron stars; interstellar medium; interstellar magnetic fields; non-thermal radiation sources; extended radiation sources; x-ray astronomy
Detecting Biosignatures in Nearby Rocky Exoplanets Using High-contrast Imaging and Medium-resolution Spectroscopy with the Extremely Large Telescope

In the upcoming decades, one of the primary objectives in exoplanet science is to search for habitable planets and signs of extraterrestrial life in the Universe. Signs of life can be indicated by thermal-dynamical imbalance in terrestrial planet atmospheres. O2 and CH4 in the modern Earth's atmosphere are such signs, commonly termed biosignatures. These biosignatures in exoplanetary atmospheres can potentially be detectable through high-contrast imaging instruments on future extremely large telescopes. To quantify the signal-to-noise ratio (S/N) with extremely large telescopes, we select up to 10 nearby rocky planets and simulate medium-resolution (R ~ 1000) direct imaging of these planets using the Mid-infrared ELT Imager and Spectrograph (ELT/METIS, 3-5.6 μm) and the High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (ELT/HARMONI, 0.5-2.45 μm). We calculate the S/N for the detection of biosignatures including CH4, O2, H2O, and CO2. Our results show that GJ 887 b has the highest detection of S/N for biosignatures, and Proxima Cen b exhibits the only detectable CO2 among the targets for ELT/METIS direct imaging. We also investigate the TRAPPIST-1 system, the archetype of nearby transiting rocky planet systems, and compare the biosignature detection of transit spectroscopy with JWST versus direct spectroscopy with ELT/HARMONI. Our findings indicate JWST is more suitable for detecting and characterizing the atmospheres of transiting planet systems such as TRAPPIST-1 that are relatively further away and have smaller angular separations than more nearby nontransiting planets.

Keywords: direct imaging; exoplanet atmospheric composition; biosignatures; extrasolar rocky planets
An Investigation of Fragmentation in the Disk Instability Model for Giant Planet Formation

We investigate a few issues regarding fragmentation in the disk instability model for giant planet formation—specifically, initial clump mass (Mp), fragmentation region, and fragmentation starting time, ending time, and duration. By running calculations over a wide parameter space and using an evolutionary model of protoplanetary disks, we study dependence on properties of the parent cloud core of the protostar+disk system. We investigate evolution of Mp-R relationship for clumps forming at different times during the disk evolution. We find that, in general, for the same radius, Mp changes slightly with time, first decreasing and then increasing. In different disks, for the same radius, Mp does not change significantly with ω, decreases with MMCC, and increases with TMCC, where ω, MMCC, and TMCC are angular velocity, mass, and temperature of a parent core. Fragmentation might occur most probably at 20-200 au, at 200-450 au with less probability, and at >450 au with small probability. Mp might be most probably between 3-35MJ, between 35-80MJ with less probability, and >80MJ with small probability. The ranges of the fragmentation starting time, ending time, and duration are (1-3) × 105 yr, $(2\mbox{--}25)\times {10}^{5}\,\mathrm{yr}$ , and $(0.1\mbox{--}25)\times {10}^{5}\,\mathrm{yr}$ , respectively. We derive an analytical formula that shows dependence of ${M}_{{\rm{p}}}$ on disk properties and can be used to understand numerical calculations. We tentatively use our calculations to understand exoplanet observations.

Keywords: exoplanet formation; exoplanet systems; planet formation; solar system formation
High-frequency Radio Imaging of 3CR 403.1 with the Sardinia Radio Telescope

We present multifrequency observations of the radio source 3CR 403.1, a nearby (z = 0.055), extended (~0.5 Mpc) radio galaxy hosted in a small galaxy group. Using new high-frequency radio observations from the Sardinia Radio Telescope (SRT), augmented with archival low-frequency radio observations, we investigated radio spectral and polarimetric properties of 3CR 403.1. From the MHz-to-GHz spectral analysis, we computed the equipartition magnetic field in the lobes to be B eq = 2.4 μG and the age of the source to be ~100 Myr. From the spectral analysis of the diffuse X-ray emission we measured the temperature and density of the intracluster medium (ICM). From the SRT observations, we discovered two regions where the radio flux density is below the background value. We computed the Comptonization parameter both from the radio and from the X-ray observations to test whether the Sunyaev-Zel'dovich effect is occurring here and found a significant tension between the two estimates. If the negative signal is considered as real, then we speculate that the discrepancy between the two values could be partially caused by the presence of a nonthermal bath of mildly relativistic ghost electrons. From the polarimetric radio images, we find a net asymmetry of the Faraday rotation between the two prominent extended structures of 3CR 403.1 and constrain the magnetic field strength in the ICM to be 1.8-3.5 μG. The position of 3CR 403.1 in the magnetic field-gas density plane is consistent with the trend reported in the literature between central magnetic field and central gas density.

Keywords: extragalactic astronomy; intergalactic medium; galaxy clusters; active galactic nuclei; radio jets
4C 18.47: A Recoiling AGN Candidate in the Radio and Infrared

Recoiling active galactic nuclei (AGNs) can be formed after the merging of two galaxies and their central supermassive black holes. A novel method recently revealed a handful of recoiling AGN candidates. We report on the arcsec-scale radio structure of one of them, 4C 18.47, a prominent radio emitter. We also present its infrared light curve, indicating significant long-term variability.

Keywords: radio active galactic nuclei; infrared sources; supermassive black holes; galaxy mergers
LensingETC: A Tool to Optimize Multifilter Imaging Campaigns of Galaxy-scale Strong Lensing Systems

Imaging data is the principal observable required to use galaxy-scale strong lensing in a multitude of applications in extragalactic astrophysics and cosmology. In this paper, we develop Lensing Exposure Time Calculator (LENSINGETC; https://github.com/ajshajib/LensingETC) to optimize the efficiency of telescope-time usage when planning multifilter imaging campaigns for galaxy-scale strong lenses. This tool simulates realistic data tailored to specified instrument characteristics and then automatically models them to assess the power of the data in constraining lens model parameters. We demonstrate a use case of this tool by optimizing a two-filter observing strategy (in the IR and ultraviolet-visual (UVIS)) within the limited exposure time per system allowed by a Hubble Space Telescope (HST) Snapshot program. We find that higher resolution is more advantageous to gain constraining power on the lensing observables, when there is a trade-off between signal-to-noise ratio and resolution; for example, between the UVIS and IR filters of the HST. We also find that, whereas a point-spread function (PSF) with sub-Nyquist sampling allows the sample mean for a model parameter to be robustly recovered for both galaxy-galaxy and point-source lensing systems, a sub-Nyquist-sampled PSF introduces a larger scatter than a Nyquist-sampled one in the deviation from the ground truth for point-source lens systems.

Keywords: strong gravitational lensing; astronomy software; astronomical methods
Evidence for a Buried AGN in an Extremely Bright Dusty Galaxy at z = 2

We present preliminary results of a submillimeter spectral line survey of a strongly lensed dusty star-forming galaxy (DSFG) at z ∼ 2, near the peak epoch of cosmic star formation. We use data from the Submillimeter Array, which recently completed a systems upgrade that substantially increased the instantaneous bandwidth. Focusing on the brightest spectral lines of CO and atomic carbon, we characterize the interstellar medium properties of this galaxy. We find highly excited CO and [C I] emission, and a large [C I] line ratio implies a higher excitation temperature than other extreme high-redshift sources. Based on this evidence, we infer that the source likely hosts a dust-obscured active galactic nucleus similar to other well-studied DSFGs.

Keywords: radio astronomy; submillimeter astronomy; starburst galaxies; active galactic nuclei; interferometry; high-redshift galaxies; galaxies; co line emission; spectral line identification
Discovery of a Remarkably Powerful Broad Absorption-line Quasar Outflow in SDSS J135246.37+423923.5

Broad absorption-line (BAL) features in quasar spectra reveal an unambiguous signature of energetic outflows from central supermassive black holes, and thus, BAL quasars are prime targets for investigating the potential process of luminous quasar feedback on galaxies. We analyzed the rest-UV spectrum of an "overlapping trough" iron low-ionization broad absorption-line quasar (FeLoBAL) SDSS J135246.37+423923.5 using the novel spectral synthesis code SimBAL and discovered an extraordinarily fast and energetic BAL outflow. Our analysis revealed outflow velocities reaching ∼-38,000 km s-1 with a velocity width of ∼ 10,000 km s-1, which is the largest FeLoBAL outflow velocity measured to date. The column density of the outflow gas is log N_{H} ∼23.2 cm-1 with the log kinetic luminosity log L_{KE} ∼48.1 (erg s-1), which exceeds the bolometric luminosity of the quasar and is energetic enough to effectively drive quasar feedback. The energy estimate for the outflow is far greater than the estimates from any BAL object previously reported. The object also shows "anomalous reddening" and a significant scattered component that we were able to model with SimBAL. We found the first definitive case for radiation filtering in an additional zero-velocity absorption component that required an absorbed continuum to produce the particular absorption lines observed (Mg II, Al III, and Al II) without also producing the high-ionization lines such as C IV.

Keywords: broad-absorption line quasar; spectroscopy; high-luminosity active galactic nuclei; galaxies
Star-Gas Surface Density Correlations in 12 Nearby Molecular Clouds. I. Data Collection and Star-sampled Analysis

We explore the relation between the stellar mass surface density and the mass surface density of molecular hydrogen gas in 12 nearby molecular clouds that are located at <1.5 kpc distance. The sample clouds span an order-of-magnitude range in mass, size, and star formation rates. We use thermal dust emission from Herschel maps to probe the gas surface density and the young stellar objects from the most recent Spitzer Extended Solar Neighborhood Archive catalog to probe the stellar surface density. Using a star-sampled nearest neighbor technique to probe the star-gas surface density correlations at the scale of a few parsecs, we find that the stellar mass surface density varies as a power law of the gas mass surface density, with a power-law index of ∼2 in all the clouds. The consistent power-law index implies that star formation efficiency is directly correlated with gas column density, and no gas column density threshold for star formation is observed. We compare the observed correlations with the predictions from an analytical model of thermal fragmentation and with the synthetic observations of a recent hydrodynamic simulation of a turbulent star-forming molecular cloud. We find that the observed correlations are consistent for some clouds with the thermal fragmentation model and can be reproduced using the hydrodynamic simulations.

Keywords: star formation; star forming regions; molecular clouds; protostars; young stellar objects; early stellar evolution; far infrared astronomy; infrared astronomy; scaling relations; dust continuum emission; hydrodynamical simulations