adsabs/SciX_UAT_keywords huggingface dataset:
Mapping Dust Attenuation and the 2175 Å Bump at Kiloparsec Scales in Nearby Galaxies

We develop a novel approach to measure the dust attenuation properties of galaxies, including the dust opacity, the shape of the attenuation curve, and the strength of the 2175 Å absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve with an absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine the dust attenuation properties. We apply this method to investigate dust attenuation on kiloparsec scales using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find that the attenuation curve slope and the 2175 Å bump in both the optical and NUV span a wide range at kiloparsec scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), the minor-to-major axis ratio (b/a) of the galaxies, and the location of spaxels within individual galaxies. The 2175 Å bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b/a, and the locations within individual galaxies are all weak. All of these trends appear to be independent of the stellar mass of the galaxies. Our results support the scenario that the variation of the 2175 Å bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.

Keywords: interstellar dust
Revisiting the Hubble Constant, Spatial Curvature, and Cosmography with Strongly Lensed Quasar and Hubble Parameter Observations

It is well known that time delays due to strong lensing offer the opportunity of a one-step measurement of the Hubble constant H 0 that is independent of the cosmic distance ladder. In this paper, we go further and propose a cosmological model-independent approach to simultaneously determine the Hubble constant and cosmic curvature with measurements of the time delay due to strong lensing, without any prior assumptions regarding the content of the universe. The data we use comprise the recent compilation of six well studied strongly lensed quasars, while the cosmic chronometer data are utilized to reconstruct distances via cosmographic parameters. In the framework of third-order Taylor expansion and (2, 1) order Padé approximation for cosmographic analysis, our results provide model-independent estimations of the Hubble constant ${H}_{0}={72.24}_{-2.52}^{+2.73}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and ${H}_{0}={72.45}_{-2.02}^{+1.95}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , which are well consistent with that derived from the local distance ladder by the SH0ES collaboration. The measured cosmic curvature ${{\rm{\Omega }}}_{k}={0.062}_{-0.078}^{+0.117}$ and ${{\rm{\Omega }}}_{k}={0.069}_{-0.103}^{+0.116}$ shows that zero spatial curvature is supported by the current observations of time delays due to strong lensing and cosmic chronometers. Imposing the prior of spatial flatness leads to more precise (at 1.6% level) determinations of the Hubble constant ${H}_{0}={70.47}_{-1.15}^{+1.14}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and ${H}_{0}={71.66}_{-1.57}^{+1.15}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ , values located between the results from Planck and the SH0ES collaboration. If a prior of local (SH0ES) H 0 measurement is adopted, the constraint on curvature parameter can be further improved to ${{\rm{\Omega }}}_{k}={0.123}_{-0.046}^{+0.060}$ and ${{\rm{\Omega }}}_{k}={0.101}_{-0.072}^{+0.090}$ , supporting no significant deviation from a flat universe. Finally, we also discuss the effectiveness of the Padé approximation in reconstructing the cosmic expansion history for redshifts up to z ~ 2.3, considering its better performance in the Bayes information criterion.

Keywords: strong gravitational lensing; cosmological parameters
Constraining the Low-mass End of the Black Hole Mass Function and the Active Fraction of the Intermediate-mass Black Holes

We investigate the black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF), focusing on the intermediate-mass black holes (IMBHs) with masses down to M • ∼ 104 M ⊙. Based on the active galactic nuclei (AGNs) with a detected broad Hα emission line, we construct a sample of 14,242 AGNs at redshift z < 0.35, including 243 IMBHs with M • < 106 M ⊙. By jointly modeling the BHMF and ERDF via the maximum posterior estimation, we find that the BHMF peaks at ∼106 M ⊙ and exhibits a relatively constant value of 10‑4 Mpc‑3 dex‑1 at the low-mass end. By comparing the derived BHMF of type 1 AGNs with the galaxy mass function based on the updated black hole mass–host galaxy stellar mass relation, we derive the active fraction. We also determine the active fraction for all AGNs using the upper and lower limit of the type 1 fraction. The active fraction decreases from 15%–40% for massive galaxies (M ⋆ > 1010 M ⊙) to lower than ∼2% for dwarf galaxies with M ⋆ ∼ 108 M ⊙. These results suggest that the black hole occupation fraction is expected to be ∼50% for low-mass galaxies (M ⋆ ∼ 108.5–109 M ⊙) if the duty cycle is similar between IMBHs and supermassive black holes.

Keywords: active galactic nuclei; intermediate-mass black holes; supermassive black holes
Delay Time Distributions of Type Ia Supernovae from Galaxy and Cosmic Star Formation Histories

We present analytical reconstructions of SN Ia delay time distributions (DTDs) by way of two independent methods: by a Markov Chain Monte Carlo best-fit technique comparing the volumetric SN Ia rate history to today's compendium cosmic star formation history, and second through a maximum likelihood analysis of the star formation rate histories of individual galaxies in the GOODS/CANDELS field, in comparison to their resultant SN Ia yields. We adopt a flexible skew-normal DTD model, which could match a wide range of physically motivated DTD forms. We find a family of solutions that are essentially exponential DTDs, similar in shape to the β ≈ -1 power-law DTDs, but with more delayed events (>1 Gyr in age) than prompt events (<1 Gyr). Comparing these solutions to delay time measures separately derived from field galaxies and galaxy clusters, we find the skew-normal solutions can accommodate both without requiring a different DTD form in different environments. These model fits are generally inconsistent with results from single-degenerate binary population synthesis models, and are seemingly supportive of double-degenerate progenitors for most SN Ia events.

Keywords: type ia supernovae; supernovae
Exploring the 100 au Scale Structure of the Protobinary System NGC 2264 CMM3 with ALMA

We have observed the young protostellar system NGC 2264 CMM3 in the 1.3 mm and 2.0 mm bands at a resolution of about 0"1 (70 au) with ALMA. The structures of two distinct components, CMM3A and CMM3B, are resolved in the continuum images of both bands. CMM3A has an elliptical structure extending along the direction almost perpendicular to the known outflow, while CMM3B reveals a round shape. We have fitted two 2D Gaussian components to the elliptical structure of CMM3A and CMM3B and have separated the disk and envelope components for each source. The spectral index α between 2.0 and 0.8 mm is derived to be 2.4-2.7 and 2.4-2.6 for CMM3A and CMM3B, respectively, indicating optically thick dust emission and/or grain growth. A velocity gradient in the disk/envelope direction is detected for CMM3A in the CH3CN, CH3OH, and 13CH3OH lines detected in the 1.3 mm band, which can be interpreted as the rotation of the disk/envelope system. From this result, the protostellar mass of CMM3A is roughly evaluated to be 0.1-0.5 M⊙ by assuming Keplerian rotation. The mass accretion rate is thus estimated to be 5 × 10-5 - 4 × 10-3 M⊙ yr-1, which is higher than the typical mass accretion rate of low-mass protostars. The OCS emission line shows a velocity gradient in both outflow direction and disk/envelope direction. A hint of outflow rotation is found, and the specific angular momentum of the outflow is estimated to be comparable to that of the disk. These results provide us with novel information on the initial stage of a binary/multiple system.

Keywords: star formation; protostars; interstellar medium; interstellar molecules; young stellar objects
GW200115: A Nonspinning Black Hole-Neutron Star Merger

GW200115 was the second merger of a black hole and a neutron star confidently detected through gravitational waves. Inference on the signal allows for a large black hole spin misaligned with the orbital angular momentum, but shows little support for aligned spin values. We show that this is a natural consequence of measuring the parameters of a black hole-neutron star binary with nonspinning components while assuming the priors used in the LIGO-Virgo-KAGRA analysis. We suggest that, a priori, a nonspinning binary is more consistent with current astrophysical understanding.

Keywords: stellar mass black holes; gravitational wave astronomy; stellar rotation
Search for Collisionally Pumped 1720 MHz OH Masers in Star-forming Regions: A VLA Survey of 18 cm OH Masers toward 80 Class I Methanol Masers

Class I methanol masers (cIMMs) and 1720 MHz OH masers are believed to arise from a common collisional pumping mechanism, and both trace shocked gas regions in supernova remnants (SNRs). However, their coexistence in star formation regions (SFRs) and their association with a front of bipolar outflow (a source of shock-stimulated collisional pumping) remain unclear. To search for collisionally pumped OH(1720) masers, we conducted a Very Large Array survey of the 18 cm OH masers and continuum emission toward a sample of 80 SFRs associated with 44 GHz cIMMs. Main-line OH maser emission was detected in 50% of the sample, and OH(1720) maser emission was detected in 20%. Continuum emission was detected in 28% of sources. A catalog of the detected OH masers is presented. Individual OH masers are found in close proximity, and the regions of masers of different transitions are often overlapping. A typical linear projected offset between the OH(1720) and OH(1665) masers is ~0.04 pc. A remarkable number of ~81% of the OH(1720) masers are associated with the continuum emission. The median separation between the targeted 44 GHz cIMMs and OH(1720) masers is ~0.2 pc, which is similar to reported distances between cIMMs and H II regions. The observed properties of the detected OH(1720) masers are different from those in SNRs and indicate that a nonlocal line overlap mechanism is responsible for their excitation. Thus, while both 44 GHz cIMMs and OH(1720) masers trace shocked gas in SNRs, physical conditions favorable for excitation of cIMMs, but not OH(1720) masers, are present in SFRs.

Keywords: hydroxyl masers; astrophysical masers; very large array; shocks; surveys
Thirty Years of Radio Observations of Type Ia SN 1972E and SN 1895B: Constraints on Circumstellar Shells

We have imaged 35 yr of archival Very Large Array observations of the nearby (dL = 3.15 Mpc) Type Ia supernovae SN 1972E and SN 1895B between 9 and 121 yr post-explosion. No radio emission is detected, constraining their radio luminosities to be Lν,8.5GHz < 6.0 × 1023 erg s-1 Hz-1 45 yr post-explosion and Lν,8.5GHz < 8.9 × 1023 erg s-1 Hz-1 121 yr post-explosion, respectively. These limits imply a clean circumstellar medium (CSM), with n < 0.9 cm-3 out to radii of a few ×1018 cm, if the SN blast wave is expanding into uniform density material. We also constrain the presence of CSM shells surrounding the progenitor of SN 1972E. We rule out essentially all medium and thick shells with masses of 0.05-0.3 M⊙ at radii between ∼1017 and 1018 cm, and thin shells at specific radii with masses down to ≲0.01 M⊙. These constraints rule out swaths of parameter space single and double degenerate progenitor scenarios, including recurrent nova, core-degenerate objects, ultra-prompt explosions, and white dwarf (WD) mergers with delays of a few hundred years between the onset of merger and explosion. Allowed progenitors include WD-WD systems with a significant (>104 yr) delay from the last episode of common envelope evolution and single degenerate systems undergoing recurrent nova—provided that the system has been in the nova phase for ≳104 yr, such that a large (>1018 cm) cavity has been evacuated. Future multi-epoch observations of additional intermediate-aged SNe Ia will provide a comprehensive view of the large-scale CSM around these explosions.

Keywords: circumstellar matter; supernovae; type ia supernovae; radio continuum emission
Detecting Interstellar Objects through Stellar Occultations

Stellar occultations have been used to search for Kuiper Belt and Oort Cloud objects. We propose a search for interstellar objects based on the characteristic durations (∼0.1 s) of their stellar occultation signals and high inclination relative to the ecliptic plane. An all-sky monitoring program of all ∼7 × 106 stars with R ≲ 12.5 using 1-m telescopes with 0.1 s cadences is predicted to discover ∼1 interstellar object per year.

Keywords: asteroids; meteors; stellar occultation
Electron and Proton Energization in 3D Reconnecting Current Sheets in Semirelativistic Plasma with Guide Magnetic Field

Using 3D particle-in-cell simulation, we characterize energy conversion, as a function of guide magnetic field, in a thin current sheet in semirelativistic plasma, with relativistic electrons and subrelativistic protons. There, magnetic reconnection, the drift-kink instability (DKI), and the flux-rope kink instability all compete and interact in their nonlinear stages to convert magnetic energy to plasma energy. We compare fully 3D simulations with 2D in two different planes to isolate reconnection and DKI effects. In zero guide field, these processes yield distinct energy conversion signatures: ions gain more energy than electrons in 2Dxy (reconnection), while the opposite is true in 2Dyz (DKI), and the 3D result falls in between. The flux-rope instability, which occurs only in 3D, allows more magnetic energy to be released than in 2D, but the rate of energy conversion in 3D tends to be lower. Increasing the guide magnetic field strongly suppresses DKI, and in all cases slows and reduces the overall amount of energy conversion; it also favors electron energization through a process by which energy is first stored in the motional electric field of flux ropes before energizing particles. Understanding the evolution of the energy partition thus provides insight into the role of various plasma processes, and is important for modeling radiation from astrophysical sources such as accreting black holes and their jets.

Keywords: plasma astrophysics; high energy astrophysics; active galactic nuclei; plasma physics; astrophysical black holes; magnetic fields
R-mode Stability of GW190814's Secondary Component as a Supermassive and Superfast Pulsar

The nature of GW190814's secondary component m2 of mass 2.50-2.67 M⊙ in the mass gap between the currently known maximum mass of neutron stars and the minimum mass of black holes is currently under hot debate. Among the many possibilities proposed in the literature, m2 was suggested to be a superfast pulsar, while its r-mode stability against runaway gravitational radiation through the Chandrasekhar-Friedman-Schutz mechanism is still unknown. Previously, Fortin et al. constructed a sample of 33 unified equations of state using the same nuclear interactions from the crust to the core consistently; from that sample we use those equations that fulfill all currently known astrophysical and nuclear physics constraints to compare the minimum frequency required for m2 to rotationally sustain a mass greater than 2.50 M⊙ with the critical frequency above which the r-mode instability occurs. We use two extreme damping models assuming that the crust is either perfectly rigid or elastic. Using the stability of 19 observed low-mass X-ray binaries as an indication that the rigid crust damping of the r-mode dominates within the models studied, we find that m2 is r-mode-stable while rotating with a frequency higher than 870.2 Hz (0.744 times its Kepler frequency of 1169.6 Hz) as long as its temperature is lower than about 3.9 × 107 K, further supporting the proposal that GW190814's secondary component is a supermassive and superfast pulsar.

Keywords: pulsars; neutron stars
The Behavior of HgMn Stars in the Far UV -4: ι CrB A

The analysis of twelve high resolution SWP spectra of the HgMn star HD 143807 A (ι CrB A) obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far-ultraviolet flux of this star remained constant over the various observations with IUE. The TESS lightcurve of ι CrB does not show evidence for periodic variability. The absence of far and mid-UV variability and the reproducibility of the brightness in the V band during the IUE observations precludes the presence of large chemical gradients over the surface of ι CrB at the epoch of the IUE observations. The analysis of six high resolution SOPHIE spectra obtained over three consecutive nights in 2007 March does not show any variations of the lines, either in reduced intensity nor in radial velocity.

Keywords: chemically peculiar stars
ALMA Band-7 Flux Density Prediction of the Haumea Ring System for Ongoing Observations

In 2017, multi-chord occultation observations found a ring around the dwarf planet (136108) Haumea, and provided direct measurements of the size and an estimate of the apparent opacity of the ring system. Based on these properties, Müller et al. estimated the thermal contribution of Haumea's ring at 20-500 μm. Here, we predict the flux densities of the ring of Haumea at ~870 μm for ongoing measurements with ALMA.

Keywords: small solar system bodies
Unsupervised Machine Learning for Exploratory Data Analysis of Exoplanet Transmission Spectra

Transit spectroscopy is a powerful tool for decoding the chemical compositions of the atmospheres of extrasolar planets. In this paper, we focus on unsupervised techniques for analyzing spectral data from transiting exoplanets. After cleaning and validating the data, we demonstrate methods for: (i) initial exploratory data analysis, based on summary statistics (estimates of location and variability); (ii) exploring and quantifying the existing correlations in the data; (iii) preprocessing and linearly transforming the data to its principal components; (iv) dimensionality reduction and manifold learning; (v) clustering and anomaly detection; and (vi) visualization and interpretation of the data. To illustrate the proposed unsupervised methodology, we use a well-known public benchmark data set of synthetic transit spectra. We show that there is a high degree of correlation in the spectral data, which calls for appropriate low-dimensional representations. We explore a number of different techniques for such dimensionality reduction and identify several suitable options in terms of summary statistics, principal components, etc. We uncover interesting structures in the principal component basis, namely well-defined branches corresponding to different chemical regimes of the underlying atmospheres. We demonstrate that those branches can be successfully recovered with a K-means clustering algorithm in a fully unsupervised fashion. We advocate for lower-dimensional representations of the spectroscopic data in terms of the main principal components, in order to reveal the existing structure in the data and quickly characterize the chemical class of a planet.

Keywords: clustering; principal component analysis; dimensionality reduction; transmission spectroscopy; radiative transfer; exoplanet atmospheres
Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images

We identify 71 distant stars in James Webb Space Telescope/NIRCam early release observations (ERO) images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small (~10°) angular separation between SMACS 0723 and the Large Magellanic Cloud (LMC), it is likely that these stars are associated with the LMC outskirts or the Leading Arm. This is further bolstered by a spectral energy distribution (SED) analysis, which suggests an excess of stars at a physical distance of 40-100 kpc, consistent with being associated with or located behind the Magellanic system. In particular, we find that the overall surface density of stars brighter than 27.0 mag in the field of SMACS 0723 is ~2.3 times that of stars in a blank field with similar Galactic latitude (the North Ecliptic Pole Time Domain Field), and that the density of stars in the SMACS 0723 field with SED-derived distances consistent with the Magellanic system is ~6.1 times larger than that of the blank field. The candidate stars at these distances are consistent with a stellar population at the same distance modulus with [Fe/H] = -1.0 and an age of ~5.0 Gyr. On the assumption that all of the 71 stars are associated with the LMC, then the stellar density of the LMC at the location of the SMACS 0723 field is ~740 stars kpc-3, which helps trace the density of stars in the LMC outskirts.

Keywords: galactic archaeology; stellar spectral types; james webb space telescope
X-Ray Coronal Properties of Swift/BAT-selected Seyfert 1 Active Galactic Nuclei

The corona is an integral component of active galactic nuclei (AGNs) which produces the bulk of the X-ray emission above 1-2 keV. However, many of its physical properties and the mechanisms powering this emission remain a mystery. In particular, the temperature of the coronal plasma has been difficult to constrain for large samples of AGNs, as constraints require high-quality broadband X-ray spectral coverage extending above 10 keV in order to measure the high-energy cutoff, which provides constraints on the combination of coronal optical depth and temperature. We present constraints on the coronal temperature for a large sample of Seyfert 1 AGNs selected from the Swift/BAT survey using high-quality hard X-ray data from the NuSTAR observatory combined with simultaneous soft X-ray data from Swift/XRT or XMM-Newton. When applying a physically motivated, nonrelativistic disk-reflection model to the X-ray spectra, we find a mean coronal temperature kT e = 84 ± 9 keV. We find no significant correlation between the coronal cutoff energy and accretion parameters such as the Eddington ratio and black hole mass. We also do not find a statistically significant correlation between the X-ray photon index, Γ, and Eddington ratio. This calls into question the use of such relations to infer properties of supermassive black hole systems.

Keywords: active galactic nuclei; black holes; x-ray sources; seyfert galaxies