adsabs/SciX_UAT_keywords huggingface dataset:
Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS

Supernova (SN) 1987A is the nearest supernova in ~400 yr. Using the JWST MIRI Medium Resolution Spectrograph, we spatially resolved the ejecta, equatorial ring (ER), and outer rings in the mid-infrared 12,927 days (35.4 yr) after the explosion. The spectra are rich in line and dust continuum emission, both in the ejecta and the ring. The broad emission lines (280-380 km s-1 FWHM) that are seen from all singly-ionized species originate from the expanding ER, with properties consistent with dense post-shock cooling gas. Narrower emission lines (100-170 km s-1 FWHM) are seen from species originating from a more extended lower-density component whose high ionization may have been produced by shocks progressing through the ER or by the UV radiation pulse associated with the original supernova event. The asymmetric east-west dust emission in the ER has continued to fade, with constant temperature, signifying a reduction in dust mass. Small grains in the ER are preferentially destroyed, with larger grains from the progenitor surviving the transition from SN into SNR. The ER dust is fit with a single set of optical constants, eliminating the need for a secondary featureless hot dust component. We find several broad ejecta emission lines from [Ne II], [Ar II], [Fe II], and [Ni II]. With the exception of [Fe II] 25.99 μm, these all originate from the ejecta close to the ring and are likely to be excited by X-rays from the interaction. The [Fe II] 5.34 to 25.99 μm line ratio indicates a temperature of only a few hundred K in the inner core, which is consistent with being powered by 44 Ti decay.

Keywords: core-collapse supernovae; supernova remnants; high energy astrophysics; circumstellar dust
Evolutionary Relationship between Sunspot Groups and Soft X-Ray Flares over Solar Cycles 21-25

Studying the interaction between solar flares and sunspot groups (SGs) is crucial for understanding and predicting solar activity. We examined the distribution, correlation, and flaring rates in the northern and southern hemispheres to reveal the relationship between different classes of soft X-ray (SXR) flares and different magnetic classifications of SGs. We discovered a significant north-south asymmetry in SXR flares and SG distribution over Solar Cycles (SC) 21-25. In the rising phase of SC24, the northern hemisphere's activity is significantly excessive. In the declining phase of SC24, the southern hemisphere's activity becomes significantly excessive. The total numbers of various SXR flares and SGs vary between the northern and southern hemispheres over the solar cycle. B-class flares are negatively correlated with all SGs at maximum but positively correlated at minimum. C-class flares correlate best with α and β SGs. M-class flares correlate best with β γ δ and β SGs. X-class flares correlate highest with β γ δ SGs. The flaring rate of each flare class is lowest for α SGs and highest for β γ δ SGs. The flaring rates are higher in the southern hemisphere than in the northern hemisphere. Our results demonstrate that solar flares originate from different sources of solar active regions; the high-energy flares tend to be caused by more complex magnetic fields.

Keywords: solar flares; sunspot groups; solar activity
The Gas Accretion Rate of Star-forming Galaxies over the Last 4 Gyr

Star-forming galaxies are believed to replenish their atomic gas reservoir, which is consumed in star formation, through accretion of gas from their circumgalactic mediums (CGMs). However, there are few observational constraints today on the gas accretion rate in external galaxies. Here, we use our recent measurement of the scaling relation between the atomic hydrogen (H I) mass M H I and the stellar mass M * in star-forming galaxies at z ≈ 0.35, with the relations between the star formation rate (SFR) and M *, and the molecular gas mass M Mol and M *, and the assumption that star-forming galaxies evolve along the main sequence, to determine the evolution of the neutral gas reservoir and the average net gas accretion rate onto the disks of star-forming galaxies over the past 4 Gyr. For galaxies with M * ≳ 109 M ⊙ today, we find that both M * and M H I in the disk have increased, while M Mol has decreased, since z ≈ 0.35. The average gas accretion rate onto the disk over the past 4 Gyr is similar to the average SFR over this period, implying that main-sequence galaxies have maintained a stable H I reservoir, despite the consumption of gas in star formation. We obtain an average net gas accretion rate (over the past 4 Gyr) of ≈6 M ⊙ yr-1 for galaxies with the stellar mass of the Milky Way. At low redshifts, z ≲ 0.4, the reason for the decline in the cosmic SFR density thus appears to be the inefficiency in the conversion of atomic gas to molecular gas, rather than insufficient gas accretion from the CGM.

Keywords: galaxy evolution; radio spectroscopy; accretion
The Sloan Digital Sky Survey Reverberation Mapping Project: Investigation of Continuum Lag Dependence on Broad-line Contamination and Quasar Properties

This work studies the relationship between accretion-disk size and quasar properties, using a sample of 95 quasars from the Sloan Digital Sky Survey Reverberation Mapping Project with measured lags between the g and i photometric bands. Our sample includes disk lags that are both longer and shorter than predicted by the Shakura and Sunyaev model, requiring explanations that satisfy both cases. Although our quasars each have one lag measurement, we explore the wavelength-dependent effects of diffuse broad-line region (BLR) contamination through our sample's broad redshift range, 0.1 < z < 1.2. We do not find significant evidence of variable diffuse Fe II and Balmer nebular emission in the rms spectra, nor from Anderson-Darling tests of quasars in redshift ranges with and without diffuse nebular emission falling in the observed-frame filters. Contrary to previous work, we do not detect a significant correlation between the measured continuum and BLR lags in our luminous quasar sample, similarly suggesting that our continuum lags are not dominated by diffuse nebular emission. Similar to other studies, we find that quasars with larger-than-expected continuum lags have lower 3000 Å luminosities, and we additionally find longer continuum lags with lower X-ray luminosities and black hole masses. Our lack of evidence for diffuse BLR contribution to the lags indicates that the anticorrelation between continuum lag and luminosity is not likely to be due to the Baldwin effect. Instead, these anticorrelations favor models in which the continuum lag increases in lower-luminosity active galactic nuclei, including scenarios featuring magnetic coupling between the accretion disk and X-ray corona, and/or ripples or rims in the disk.

Keywords: quasars; active galactic nuclei; supermassive black holes
Constraining Cosmic-Ray Ionization Rates and Chemical Timescales in Massive Hot Cores

Several studies have demonstrated that the cosmic-ray ionization rate is highly variable in the interstellar medium. However, constraints of this rate for several regions, including those that contain hot cores, are lacking. Hot cores are appealing sources to study given their rich chemical complexity. The chemistry of these cores can be influenced by both their cosmic-ray ionization rates and their warm-up timescales; however, understanding the chemical response to these parameters requires further investigation. We study these effects using the astrochemical hot-core modeling code MAGICKAL, in which we construct a grid of 81 models using nine ionization rates and nine warm-up timescales. We also simulate local thermodynamic equilibrium radiative transfer for these models to obtain results that can be directly compared with observations. We compare molecular emission of these models with observations toward NGC 6334 IRS 1, NGC 7538 IRS 1, W3(H2O), and W33A in an effort to constrain their cosmic-ray ionization rates and warm-up timescales. Our best fits to the observations suggest that these sources possess elevated cosmic-ray ionization rates, compared to the canonical value of 1.3 × 10-17 s-1 used in previous modeling studies, and rapid warm-up timescales. We also demonstrate that there exists a strong correlation between the cosmic-ray ionization rate and the total hydrogen column density of a source and a strong correlation between the warm-up timescale and total source mass. Furthermore, these relationships are in good agreement with other theoretical studies.

Keywords: astrochemistry; cosmic rays; line intensities; chemical abundances; massive stars
Objectively Determining States of the Solar Wind Using Machine Learning

Conclusively determining the states of the solar wind will aid in tracing the origins of those states to the Sun, and in the process help to find the wind's origin and acceleration mechanism(s). Prior studies have characterized the various states of the wind, making lists that are only partially based on objective criteria; different approaches obtain substantially different results. To uncover the unbiased states of the solar wind, we use "k-means clustering"—an unsupervised machine learning method—including constructed multipoint variables. The method allows exploration of different descriptive state variables and numbers of fundamental states (clusters). We show that the clusters reveal structures similar to those found by more ad hoc means, including coronal hole wind, interplanetary coronal mass ejections, "slow wind" (better: noncoronal hole flow), "pseudostreamers," and stream interaction regions, but with differences that should be useful in refining our previous ideas. These results demonstrate the viability of the approach and warrant further study to understand the origin of remaining discrepancies. Complexity in k-means characterization of the wind may ultimately point to complexity at the source; studies closer to the Sun with Parker Solar Probe will help. We confirm the utility of a set of variables that can serve as a proxy for composition measurements. This proxy permits studies at high time resolution and where composition is not available. This and our recently developed unsupervised multivariate clustering technique are expected to be beneficial in the automated identification of structures and events in a variety of studies.

Keywords: interplanetary physics; solar wind; interplanetary turbulence; interplanetary magnetic fields; solar coronal mass ejections
The Sloan Digital Sky Survey Reverberation Mapping Project: The MBH-Host Relations at 0.2 ≲ z ≲ 0.6 from Reverberation Mapping and Hubble Space Telescope Imaging

We present the results of a pilot Hubble Space Telescope (HST) imaging study of the host galaxies of ten quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Probing more than an order of magnitude in black hole (BH) and stellar masses, our sample is the first statistical sample to study the BH-host correlations beyond z > 0.3 with reliable BH masses from reverberation mapping rather than from single-epoch spectroscopy. We perform image decomposition in two HST bands (UVIS-F606W and IR-F110W) to measure host colors and estimate stellar masses using empirical relations between broadband colors and the mass-to-light ratio. The stellar masses of our targets are mostly dominated by a bulge component. The BH masses and stellar masses of our sample broadly follow the same correlations found for local RM active galactic nuclei and quiescent bulge-dominant galaxies, with no strong evidence of evolution in the ${M}_{\mathrm{BH}}\mbox{--}{M}_{* ,\mathrm{bulge}}$ relation to z ∼ 0.6. We further compare the host light fraction from HST imaging decomposition to that estimated from spectral decomposition. We find a good correlation between the host fractions derived with both methods. However, the host fraction derived from spectral decomposition is systematically smaller than that from imaging decomposition by ∼30%, indicating different systematics in both approaches. This study paves the way for upcoming more ambitious host galaxy studies of quasars with direct RM-based BH masses at high redshift.

Keywords: black hole physics; quasars; active galaxies; surveys
A Radio Flare in the Long-lived Afterglow of the Distant Short GRB 210726A: Energy Injection or a Reverse Shock from Shell Collisions?

We present the discovery of the radio afterglow of the short gamma-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of z ∼ 2.4. While radio observations commenced ≲1 day after the burst, no radio emission was detected until ∼11 days. The radio afterglow subsequently brightened by a factor of ∼3 in the span of a week, followed by a rapid decay (a "radio flare"). We find that a forward shock afterglow model cannot self-consistently describe the multiwavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of ≈5. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of ≈4, or a reverse shock from a shell collision are viable solutions to match the broadband behavior. At z ∼ 2.4, GRB 210726A is among the highest-redshift short GRBs discovered to date, as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by ≲10 days after the burst, potentially missing these late-rising, luminous radio afterglows.

Keywords: gamma-ray bursts; high energy astrophysics; radio astronomy; time domain astronomy
High Spatial and Spectral Resolution Observations of the Forbidden 1.707 μm Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism

We present observations obtained with the 10 m Keck telescopes of the forbidden SO a1Δ → X3Σ- rovibronic transition at 1.707 μm on Io while in eclipse. We show its spatial distribution at a resolution of ∼0"12 and a spectral resolution of R ∼ 2500, as well as disk-integrated spectra at a high spectral resolution (R ∼ 15,000). Both the spatial distribution and the spectral shape of the SO emission band vary considerably across Io and over time. In some cases the SO emissions either in the core or the wings of the emission band can be identified with volcanoes, but the largest areas of SO emissions usually do not coincide with known volcanoes. We suggest that the emissions are caused by a large number of stealth plumes, produced through the interaction of silicate melts with superheated SO2 vapor at depth. The spectra, in particular the elevated wing of the emission band near 1.69 μm, and their spatial distribution strongly suggest the presence of nonlocal thermodynamic equilibrium processes in addition to the direct ejection of excited SO from the (stealth and other) volcanic vents. * In memory of Donald Charles Backer.

Keywords: galilean satellites; planetary atmospheres; near infrared astronomy
First Detection in Space of the High-energy Isomer of Cyanomethanimine: H2CNCN

We report the first detection in the interstellar medium of N-cyanomethanimine (H2CNCN), the stable dimer of HCN of highest energy and the most complex organic molecule identified in space containing the prebiotically relevant NCN backbone. We have identified a plethora of a-type rotational transitions with 3 ≤ J up ≤ 11 and K a ≤ 2 that belong to this species toward the Galactic center G+0.693-0.027 molecular cloud, the only interstellar source showing the three cyanomethanimine isomers (including the Z- and E-isomers of C-cyanomethanimine, HNCHCN). We have derived a total column density for H2CNCN of (2.9 ± 0.1) × 1012 cm‑2, which translates into a total molecular abundance with respect to H2 of (2.1 ± 0.3) × 10‑11. We have also revisited the previous detection of E- and Z-HNCHCN and found a total C/N-cyanomethanimine abundance ratio of 31.8 ± 1.8 and a Z/E-HNCHCN ratio of 4.5 ± 0.2. While the latter can be explained on the basis of thermodynamic equilibrium, chemical kinetics are more likely responsible for the observed C/N-cyanomethanimine abundance ratio, where the gas-phase reaction between methanimine (CH2NH) and the cyanogen radical (CN) arises as the primary formation route.

Keywords: astrochemistry; galactic center; interstellar molecules; interstellar clouds; spectral line identification; pre-biotic astrochemistry
The US Naval Observatory VLBI Spectroscopic Catalog

Despite their importance for astrometry and navigation, the active galactic nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF) are relatively poorly understood, with key information such as their spectroscopic redshifts, AGN spectral type, and emission-/absorption-line properties generally missing from the literature. Using an updated, publicly available, state-of-the-art spectroscopic fitting code optimized for the spectra of AGNs from low to high redshift, we present a catalog of emission-line and spectral continuum parameters for 1014 unique ICRF3 objects with single-fiber spectra from the Sloan Digital Sky Survey DR16. We additionally present black hole virial mass scaling relationships that use Hα-, Hβ-, Mg II-, and C IV-based line widths, all consistent with each other, which can be used in studies of radio-loud objects across a wide range of redshifts, and we use these scaling relationships to provide derived properties such as black hole masses and bolometric luminosities for the catalog. We briefly comment on these properties for the ICRF objects, as well as their overall spectroscopic characteristics.

Keywords: black hole physics; active galaxies; quasars; catalogs
Solar Longitude Distribution of High-energy Proton Flares: Fluences and Spectra

The distribution of the longitudes of solar flares associated with the high-energy proton events called ground level events (GLEs) can be approximated by a Gaussian with a peak at ∼W60, with a full range from ∼E90 to ∼W150. The longitudes of flares associated with the top third (24 of 72) of GLEs in terms of their >430 MeV fluences (F430) are primarily distributed over E20-W100 with a skew toward disk center. This 120° span in longitude is comparable to the latitudinal spans of powerful coronal mass ejections (CMEs) from limb flares. Only 5 of 24 strong GLEs are located within the W40-80 zone of good magnetic connection to Earth. GLEs with hard spectra, i.e., a spectral index SI30/200(= log(F30/F200)) < 1.5, also tend to avoid W40-80 source regions. Three-fourths of such events (16 of 21) arise in flares outside this range. The above tendencies favor a CME-driven shock source over a flare-resident acceleration process for high-energy solar protons. GLE spectra show a trend, with broad scatter, from hard spectra for events originating in eruptive flares beyond the west limb to soft spectra for GLEs with sources near central meridian. This behavior can be explained in terms of: (1) dominant near-Sun quasi-perpendicular shock acceleration of protons for far western (>W100) GLEs; (2) quasi-parallel shock acceleration for well-connected (W40-80) GLEs, and (3) proton acceleration/trapping at CME-driven bow shocks from central meridian (E20-W20) that strike the Earth.

Keywords: solar energetic particles; solar flares; solar coronal mass ejections; solar coronal mass ejection shocks
Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander

NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonfly's science themes include investigation of Titan's prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based "life as we know it" (as might occur in the interior mantle ocean, potential cryovolcanic flows, and/or impact melt deposits) and potential "life, but not as we know it" that might use liquid hydrocarbons as a solvent (within Titan's lakes, seas, and/or aquifers). Consideration of both of these solvents simultaneously led to our initial landing site in Titan's equatorial dunes and interdunes to sample organic sediments and water ice, respectively. Ultimately, Dragonfly's traverse target is the 80 km diameter Selk Crater, at 7° N, where we seek previously liquid water that has mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan's tropical deserts in the global methane cycle. We will investigate the processes and processing rates that modify Titan's surface geology and constrain how and where organics and liquid water can mix on and within Titan. Importantly, we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonfly, along with Perseverance, is the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976.

Keywords: titan; pre-biotic astrochemistry; astrobiology; planetary atmospheres; planetary surfaces
Pan-STARRS Photometric and Astrometric Calibration

We present the details of the photometric and astrometric calibration of the Pan-STARRS1 3π Survey. The photometric goals were to reduce the systematic effects introduced by the camera and detectors, and to place all of the observations onto a photometric system with consistent zero-points over the entire area surveyed, the ≈30,000 deg2 north of δ = -30°. Using external comparisons, we demonstrate that the resulting photometric system is consistent across the sky to between 7 and 12.4 mmag depending on the filter. For bright stars, the systematic error floor for individual measurements is (σg, σr, σi, σz, σy) = (14, 14, 15, 15, 18) mmag. The astrometric calibration compensates for similar systematic effects so that positions, proper motions, and parallaxes are reliable as well. The bright-star systematic error floor for individual astrometric measurements is 16 mas. The Pan-STARRS Data Release 2 (DR2) astrometric system is tied to the Gaia DR1 coordinate frame with a systematic uncertainty of ∼5 mas.

Keywords: photometry; ccd photometry; astrometry; surveys; sky surveys; flux calibration; proper motions; astronomy databases
The Pantheon+ Analysis: Forward Modeling the Dust and Intrinsic Color Distributions of Type Ia Supernovae, and Quantifying Their Impact on Cosmological Inferences

Recent studies have shown that the observed color distributions of Type Ia supernovae (SNe Ia) can be well described by a combination of a dust distribution and an intrinsic color distribution. Using the Pantheon+ sample of 1701 SN Ia, we apply a new forward-modeling fitting method (Dust2Dust) to measure the parent dust and color distributions, including their dependence on host-galaxy mass. At each fit step, the SN Ia selection efficiency is determined from a large simulated sample that is reweighted to reflect the proposed distributions. We use five separate metrics to describe the goodness of fit: distribution of fitted light-curve color c, cosmological residual trends with c, cosmological residual scatter with c, fitted color-luminosity relationship β SALT2, and intrinsic scatter σ int. We present the results and the uncertainty in 12-dimensional space. Furthermore, we measure that the uncertainty on this modeling propagates to an upper threshold uncertainty in the equation of state of dark energy w of 0.014(1) for the Pantheon+ cosmology analysis and contributes negligible uncertainty to the Hubble constant H 0. The Dust2Dust code is made publicly available at https://github.com/djbrout/dustdriver.

Keywords: cosmology; type ia supernovae; dark energy