adsabs/SciX_UAT_keywords huggingface dataset:
Dust Evolution in the Coma of Distant, Inbound Comet C/2017 K2 (PANSTARRS)

C/2017 K2 (PANSTARRS) is an Oort Cloud comet previously observed to be active at heliocentric distances r > 20 au on what is likely its first passage through the inner solar system. We observed the comet on 2021 March 19-20 at r = 6.82 au preperihelion and 8.°35 phase angle with the Hubble Space Telescope (HST), and obtained high spatial resolution photometry and polarimetry mapping the properties of dust over the coma prior to the onset of water ice sublimation activity on the nucleus. We found clear radial gradients in the color and polarization of the coma: the F475W-F775W ( $g^{\prime} -i^{\prime} $ ) reflectance slope increased from ~4.5% per 100 nm within ~10,000 km of the nucleus up to ~7% per 100 nm by ~50,000 km, while the negative polarization in F775W ( $i^{\prime} $ ) strengthened from about -2% to -3.5% over the same range. The radial intensity profiles moreover strongly deviate from profiles simulated for stable dust grains. Near-infrared imagery obtained with the Palomar Hale Telescope on 2021 May 18 at r = 6.34 au revealed a continued absence of micron-sized grains in the tail, but showed no clear spatial gradient in JHKs colors. The observed patterns collectively appear consistent with the inner coma being optically dominated by sublimating, micron-sized water ice grains, unlike the tail of more stable, millimeter-sized grains. Finally, we evaluated these results alongside other Oort Cloud comets, and found in a reanalysis of HST observations of C/2012 S1 (ISON) that the near-nucleus polarimetric halo reported for that comet is likely an observational artifact.

Keywords: coma dust; comae; comets; long period comets
TARDIS. II. Synergistic Density Reconstruction from Lyα Forest and Spectroscopic Galaxy Surveys with Applications to Protoclusters and the Cosmic Web

In this work, we expand upon the Tomographic Absorption Reconstruction and Density Inference Scheme (TARDIS) in order to include multiple tracers while reconstructing matter density fields at Cosmic Noon (z ∼ 2-3). In particular, we jointly reconstruct the underlying density field from simulated Lyα forest observations at z ∼ 2.5 and an overlapping galaxy survey. We find that these data are synergistic, with the Lyα forest providing reconstruction of low-density regions and galaxy surveys tracing the density peaks. We find a more accurate power spectra reconstruction going to higher scales when fitting these two data sets simultaneously than when using either one individually. When applied to cosmic web analysis, we find that performing the joint analysis is equivalent to an Lyα survey with significantly increased sight-line spacing. Because we reconstruct the velocity field and matter field jointly, we demonstrate the ability to evolve the mock observed volume further to z = 0, allowing us to create a rigorous definition of a "protocluster" as regions that will evolve into clusters. We apply our reconstructions to study protocluster structure and evolution, finding for realistic survey parameters that we can provide accurate mass estimates of the z ≈ 2 structures and their z = 0 fate.

Keywords: intergalactic medium; extragalactic astronomy; lyman alpha forest; quasars; large-scale structure of the universe; cosmology; voids; intergalactic filaments
Can the Gravitational Wave Background Feel Wiggles in Spacetime?

Recently the international pulsar timing array collaboration has announced the first strong evidence for an isotropic gravitational-wave background (GWB). We propose that rapid small oscillations (wiggles) in the Hubble parameter would trigger a resonance with the propagating gravitational waves, leaving unique signatures in the GWB spectrum as sharp resonance peaks/troughs. The proposed signal can appear at all frequency ranges and is common to GWBs with arbitrary origin. The resonant signal can appear as a trough only when the GWB is primordial, and its amplitude will also be larger by one perturbation order than in the nonprimordial case. These properties serve as a smoking gun for the primordial origin of the observed GWB. We showcased the viability of the signal to near future observations using the recent NANOGrav 15 yr data.

Keywords: gravitational wave astronomy; gravitational waves; cosmology; cosmological evolution
Application of an X-Ray Clumpy Torus Model (XCLUMPY) to 10 Obscured Active Galactic Nuclei Observed with Suzaku and NuSTAR

We apply XCLUMPY, an X-ray spectral model from a clumpy torus in an active galactic nucleus (AGN), to the broadband X-ray spectra of 10 obscured AGNs observed with both Suzaku and NuSTAR. The infrared spectra of these AGNs were analyzed by Ichikawa et al. with the CLUMPY code. Because XCLUMPY adopts the same clump distribution as that in the CLUMPY, we can directly compare the torus parameters obtained from the X-ray spectra and those from the infrared spectra. The torus angular widths determined from the infrared spectra (σIR) are systematically larger than those from the X-ray data (σX); the difference ( ${\sigma }_{\mathrm{IR}}-{\sigma }_{{\rm{X}}}$ ) correlates with the inclination angle determined from the X-ray spectrum. These results can be explained by the contribution from dusty polar outflows to the observed infrared flux, which becomes more significant at higher inclinations (more edge-on views). The ratio of the hydrogen column density to the V-band extinction in the line-of-sight absorber shows a large scatter (≃1 dex) around the Galactic value, suggesting that a significant fraction of AGNs have dust-rich circumnuclear environments.

Keywords: high energy astrophysics; seyfert galaxies; astrophysical black holes; x-ray active galactic nuclei; supermassive black holes; active galactic nuclei
Discovery of a New Massive ZZ Ceti Star

Massive pulsating white dwarf stars are extremely rare, because they are the final product of intermediate-mass stars, which are less common than low-mass stars. Additionally, their small size makes them fainter than the normal-mass white dwarf stars (~0.6 M ⊙). Our motivation to look for this type of variable is to be able to study in detail their internal structure and therefore derive properties for the outcome of the evolution of intermediate mass stars, below 10 M ⊙. Using the 2.1 m Otto Struve Telescope at McDonald Observatory, we report on the discovery of a new massive pulsating white dwarf star. These stars might be massive enough that their cores have a significant crystallized portion, up to about 50%. A detailed asteroseismic study of these stars will provide important constrains on intermediate-mass stellar evolution, and the opportunity to study solid state physics at extreme conditions.

Keywords: white dwarf stars; asteroseismology; zz ceti stars; pulsating variable stars
The Origin and Evolution of Lyα Blobs in Cosmological Galaxy Formation Simulations

High-redshift Lyα blobs (LABs) are an enigmatic class of objects that have been the subject of numerous observational and theoretical investigations. It is of particular interest to determine the dominant power sources for their luminosity, as direct emission from H II regions, cooling gas, and fluorescence due to the presence of active galactic nuclei (AGNs) can all contribute significantly. In this paper, we present the first theoretical model to consider all of these physical processes in an attempt to develop a model for the origin of LABs. This is achieved by combining a series of high-resolution cosmological zoom-in simulations with ionization and Lyα radiative transfer models. We find that massive galaxies display a range of Lyα luminosities and spatial extents (which strongly depend on the limiting surface brightness used) over the course of their lives, though regularly exhibit luminosities and sizes consistent with observed LABs. The model LABs are typically powered from a combination of recombination in star-forming galaxies, as well as cooling emission from gas associated with accretion. When AGNs are included in the model, the fluorescence caused by active galactic nucleus-driven ionization can be a significant contributor to the total Lyα luminosity as well. Within our modeled mass range, there are no obvious threshold physical properties that predict the appearance of LABs, and only weak correlations of the luminosity with the physical properties of the host galaxy. This is because the emergent Lyα luminosity from a system is a complex function of the gas temperature, ionization state, and Lyα escape fraction.

Keywords: galaxies; galaxy formation; radiative transfer simulations
JWST Mid-infrared Spectroscopy Resolves Gas, Dust, and Ice in Young Stellar Objects in the Large Magellanic Cloud

In this work, we present spectra of 11 young stellar objects (YSOs) taken with the Mid-Infrared Instrument / Medium Resolution Spectroscopy (MRS) instrument on board the James Webb Space Telescope (JWST). The YSOs are located in the N79 region of the Large Magellanic Cloud (LMC), an active star-forming region with hundreds of Spitzer- and Herschel-identified YSOs and host to super star cluster (SSC) candidate H72.97-69.39. The three giant molecular clouds in N79 (East, West, and South) have varying star formation rates and stellar populations. MRS follow-up observations of four Spitzer-identified YSOs in N79 East, West, and South have revealed that what seemed to be a single, massive YSO is actually a cluster of YSOs. We discuss the emission and absorption lines of six YSOs that have complete or almost-complete spectral coverage from 4.9–27.9 μm. YSO Y3, located in N79 East, is the youngest source in this study and likely to be less than 10,000 yr old, as inferred from the prominent CH4, NH3, CH3OH, CH3OCHO, and CO2 ice absorption features. The most luminous source is the central ionizing YSO of SSC H72.97-69.39, Y4, which has dozens of fine-structure and H2 emission lines. Unlike the other YSOs in this work, Y4 has no polyaromatic hydrocarbon emission lines, due to the intense ionizing radiation destroying these large carbon-chain molecules. The mass accretion rates based on the H I (7-6) line luminosities of YSOs Y1, Y2, Y4, and Y9 range between 1.22 × 10‑4–1.89 × 10‑2 M ⊙ yr‑1. For the first time in the mid-infrared, we are able to resolve individual high-mass protostars forming in small clusters in an extragalactic environment like the LMC.

Keywords: young stellar objects; large magellanic cloud
The Abundance Pattern of α Elements in the Triangulum-Andromeda Overdensity

The close relationship between the nature of the Triangulum-Andromeda (TriAnd) overdensity and the Galactic disk has become increasingly evident in recent years. However, the chemical pattern of this overdensity (RGC = 20-30 kpc) is unique and differs from what we know of the local disk. In this study, we analyze the chemical abundances of five α elements (Mg, O, Si, Ca, and Ti) in a sample of stars belonging to the TriAnd overdensity, including stars with [Fe/H] < -1.2, to investigate the evolution of the α elements with metallicity. High-resolution spectra from Gemini North with GRACES were analyzed. Overall, the TriAnd population presents an α-element pattern that differs from that of the local disk; the TriAnd stars fall in between the local disk and the dwarf galaxies in the [X/Fe] versus [Fe/H] plane. The high [Mg/Fe] ratios obtained for the lower metallicity TriAnd stars may indicate a roughly parallel sequence to the Milky Way local disk at lower values of [Fe/H], revealing a knee shifted toward lower metallicities for the TriAnd population. Similar behavior is also exhibited in the [Ca/Fe] and [Si/Fe] ratios. However, for O and Ti the behavior of the [X/Fe] ratios shows a slight decay with decreasing metallicity. Our results reinforce the TriAnd overdensity as a unique stellar population of the Milky Way, with an abundance pattern that is different from all stellar populations studied to date. The complete understanding of the complex TriAnd population will require high-resolution spectroscopic observations of a larger sample of TriAnd stars.

Keywords: milky way disk; chemical abundances
Structure and Spectroscopic Signatures of Interstellar Sodium Isocyanate Isomers

The investigation of metal-containing interstellar molecules stands as a prolific field for current astrochemical research. However, the search for many of these systems in the interstellar medium has remained inaccessible to date due to the lack of preliminary spectroscopic data. In this context, pioneering theoretical studies have inspired quantum chemists to study new appealing candidates to enable their subsequent search in space. The aim of this study is to provide high-level theoretical spectroscopic signatures of the tetratomic system [Na, N, C, O]. We have performed a thorough exploration of its potential energy surface employing different state-of-the-art quantum chemical methods and nine different species have been characterized. Moreover, we have evaluated the stability of the most stable isomers against dissociation and explored their main isomerization processes. We therefore suggest sodium isocyanate (NaNCO,1Σ) and sodium cyanate, (NaOCN, 1Σ) as the most relevant candidates for laboratory and interstellar detection. To aid in their eventual spectral search by means of rotational spectroscopy, we report a complete set of the required spectroscopic parameters including the nuclear quadrupole coupling constants, which are needed to interpret their complex hyperfine structure. NaNCO and NaOCN present exceptionally high values of the electric dipole moment (11.4 and 13.6 Debyes, respectively at the CCSD(T,rw)/aug-cc-pVTZ level), which strongly support to perform an eventual radio astronomical search. Furthermore, both isomers exhibit rather small vibrational frequencies, which indicates that these species are certainly floppy molecules.

Keywords: astrochemistry; interstellar medium; molecular data; computational methods
A Decade of Radial-velocity Monitoring of Vega and New Limits on the Presence of Planets

We present an analysis of 1524 spectra of Vega spanning 10 yr, in which we search for periodic radial-velocity variations. A signal with a periodicity of 0.676 day and a semi-amplitude of ∼10 m s-1 is consistent with the rotation period measured over much shorter time spans by previous spectroscopic and spectropolarimetric studies, confirming the presence of surface features on this A0 star. The activity signal appears to evolve on long timescales, which may indicate the presence of failed fossil magnetic fields on Vega. TESS data reveal Vega's photometric rotational modulation for the first time, with a total amplitude of only 10 ppm. A comparison of the spectroscopic and photometric amplitudes suggests that the surface features may be dominated by bright plages rather than dark spots. For the shortest orbital periods, transit and radial-velocity injection recovery tests exclude the presence of transiting planets larger than 2 R⊕ and most non-transiting giant planets. At long periods, we combine our radial velocities with direct imaging from the literature to produce detection limits for Vegan planets and brown dwarfs out to distances of 15 au. Finally, we detect a candidate radial-velocity signal with a period of 2.43 days and a semi-amplitude of 6 m s-1. If caused by an orbiting companion, its minimum mass would be ∼20 M⊕; because of Vega's pole-on orientation, this would correspond to a Jovian planet if the orbit is aligned with the stellar spin. We discuss the prospects for confirmation of this candidate planet.

Keywords: exoplanet astronomy; exoplanet detection methods; exoplanets; stellar activity; stellar magnetic fields; photometry; radial velocity; circumstellar disks
A Multi-band Forced-photometry Catalog in the ELAIS-S1 Field

The ELAIS-S1 field will be an Legacy Survey of Space and Time Deep Drilling field, and it also has extensive multiwavelength coverage. To improve the utility of the existing data, we use The Tractor to perform forced-photometry measurements in this field. We compile data in 16 bands from the DeepDrill, VIDEO, DES, ESIS, and VOICE surveys. Using a priori information from the high-resolution fiducial images in VIDEO, we model the images in other bands and generate a forced-photometry catalog. This technique enables consistency throughout different surveys, deblends sources from low-resolution images, extends photometric measurements to a fainter magnitude regime, and improves photometric-redshift estimates. Our catalog contains over 0.8 million sources covering a 3.4 deg2 area in the VIDEO footprint and is available at 10.5281/zenodo.4540178.

Keywords: catalogs; surveys; galaxy photometry
A Taxonomy for the Configurations of Quadruply Lensed Quasars

A simple, novice-friendly scheme for classifying the image configurations of quadruply lensed quasars is proposed. With only six classes, it is intentionally coarse grained. It focuses on the kitelikeness and circularity of these configurations, or the absence thereof. Other features are deliberately ignored, their importance to professional astronomers notwithstanding. Readers are invited to test drive the scheme on a sample of 12 quadruply lensed quasar systems. The theoretical underpinnings of the scheme are described in a technical appendix.

Keywords: quasars; strong gravitational lensing
The Evolution of Disk Winds from a Combined Study of Optical and Infrared Forbidden Lines

We analyze high-resolution (Δv ≤ 10 km s-1) optical and infrared spectra covering the [O I] λ6300 and [Ne II] 12.81 μm lines from a sample of 31 disks in different evolutionary stages. Following work at optical wavelengths, we use Gaussian profiles to fit the [Ne II] lines and classify them into high-velocity component (HVC) or low-velocity component (LVC) if the line centroid is more or less blueshifted than 30 km s-1 with respect to the stellar radial velocity, respectively. Unlike for the [O I], where an HVC is often accompanied by an LVC, all 17 sources with an [Ne II] detection have either an HVC or an LVC. [Ne II] HVCs are preferentially detected toward high accretors ( ${\dot{M}}_{\mathrm{acc}}\gt {10}^{-8}$ M⊙ yr-1), while LVCs are found in sources with low ${\dot{M}}_{\mathrm{acc}}$ , low [O I] luminosity, and large infrared spectral index (n13-31). Interestingly, the [Ne II] and [O I] LVC luminosities display an opposite behavior with n13-31: as the inner dust disk depletes (higher n13-31), the [Ne II] luminosity increases while the [O I] weakens. The [Ne II] and [O I] HVC profiles are generally similar, with centroids and FWHMs showing the expected behavior from shocked gas in microjets. In contrast, the [Ne II] LVC profiles are typically more blueshifted and narrower than the [O I] profiles. The FWHM and centroid versus disk inclination suggest that the [Ne II] LVC predominantly traces unbound gas from a slow, wide-angle wind that has not lost completely the Keplerian signature from its launching region. We sketch an evolutionary scenario that could explain the combined [O I] and [Ne II] results and includes screening of hard (∼1 keV) X-rays in inner, mostly molecular, MHD winds.

Keywords: protoplanetary disks; stellar accretion disks; stellar jets
Recurrent Solar Energetic Particle Flux Enhancements Observed near Earth and Mars

The period 2016 August 1 to November 15 was characterized by the presence of corotating interaction regions (CIRs) and a few weak coronal mass ejections (CMEs) in the heliosphere. In this study we show recurrent energetic electron and proton enhancements observed near Earth (1 au) and Mars (1.43-1.38 au) during this period. The observations near Earth use data from instruments on board the Advanced Composition Explorer, the Solar and Heliospheric Observatory, and Solar Dynamics Observatory and those near Mars are from the Solar Energetic Particle, Solar Wind Ion Analyzer, and Magnetometer instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN). During this period, the energetic electron fluxes observed near Earth and Mars showed prominent periodic enhancements over four solar rotations, with major periodicities of ∼27 days and ∼13 days. Periodic radar blackouts/weakenings of radar signals at Mars were observed by the Mars Advanced Radar for Subsurface and Ionosphere Sounding/Mars Express, and are associated with these solar energetic electron enhancements. During this period, a weak CME and a high-speed stream (HSS)-related interplanetary shock could have interacted with the CIR and enhance energetic proton fluxes near 1.43-1.38 au, causing ∼27 days periodicity in proton fluxes to be significantly diminished at 1.43-1.38 au. These events also have an unexpected impact on the Martian topside ionosphere, such as topside ionospheric depletion and compression observed by the Langmuir Probe and Waves and Neutral Gas and Ion Mass Spectrometer on board MAVEN. These observations are unique not only because of the recurring nature of electron enhancements seen at two vantage points, but also because they reveal the unexpected impact of the weak CME and interplanetary shock on the Martian ionosphere, which provides new insights into the impact of CME-HSS interactions on the Martian plasma environment.

Keywords: solar coronal mass ejections; corotating streams; solar particle emission; solar energetic particles; solar system terrestrial planets; mars
RMTable2023 and PolSpectra2023: Standards for Reporting Polarization and Faraday Rotation Measurements of Radio Sources

Faraday rotation measures (RMs) have been used for many studies of cosmic magnetism, and in most cases having more RMs is beneficial for those studies. This has lead to the development of RM surveys that have produced large catalogs, as well as meta-catalogs collecting RMs from many different publications. However, it has been difficult to take full advantage of all of these RMs, as the individual catalogs have been published in many different places, and in many different formats. In addition, the polarization spectra used to determine these RMs are rarely published, limiting the ability to reanalyze data as new methods or additional observations become available. We propose a standard convention for RM catalogs, RMTable2023, and a standard for source-integrated polarized spectra of radio sources, PolSpectra2023. These standards are intended to maximize the value and utility of these data for researchers and to make them easier to access. To demonstrate the use of the RMTable2023 standard, we have produced a consolidated catalog of 55,819 RMs collected from 42 published catalogs.

Keywords: radio astronomy; spectropolarimetry
VVV J165507.19-421755.5: A Nearby T Dwarf Hidden in the Galactic Plane

We present the discovery of VVV J165507.19-421755.5, a mid-T dwarf found through ongoing unWISE-based proper motion searches. A near-infrared spectrum of this object obtained with the NIRES instrument on the Keck II telescope indicates a spectral classification of T5. Using data from the VISTA Variables in the Via Lactea (VVV) catalog with a 9 year baseline, we measure a proper motion of ( ${\mu }_{\alpha }\cos (\delta )$ , μ δ ) = (-631.0 ± 1.3, -315.0 ± 1.4) mas yr-1 and a trigonometric parallax of π abs = 66.0 ± 4.8 mas, corresponding to a distance of 15.2 ± 1.1 pc. The trigonometric parallax agrees well with our photometric distance estimate (16.1 ${}_{-3.9}^{+5.1}$ pc) assuming that VVV J165507.19-421755.5 is a single T5 dwarf. VVV J165507.19-421755.5 is a new member of the 20 parsec census.

Keywords: t dwarfs; brown dwarfs; infrared spectroscopy; spectroscopy