adsabs/SciX_UAT_keywords huggingface dataset:
The Size-Mass Relation of Post-starburst Galaxies in the Local Universe

We present a study of the size-mass relation for local post-starburst (PSB) galaxies at z ≲ 0.33 selected from the Sloan Digital Sky Survey Data Release 8. We find that PSB galaxies with stellar mass (M *) at 109 M ☉ < M * < 1012 M ☉ have a galaxy size smaller than or comparable to those of quiescent galaxies (QGs). After controlling redshift and stellar mass, the sizes of PSBs are ~13% smaller on average than those of QGs; such differences become larger and significant toward the low-M * end, especially at 109.5 M ☉ ≲ M * ≲ 1010.5 M ☉ where PSBs can be on average ~19% smaller than QGs. By comparing predictions of possible PSB evolutionary pathways from cosmological simulations, we suggest that a fast quenching of star formation following a short-lived starburst event (which might be induced by a major merger) should be the dominant pathway of our PSB sample. Furthermore, by cross-matching with group catalogs, we confirm that local PSBs at M * ≲ 1010 M ☉ are more clustered than more massive ones. PSBs residing in groups are found to be slightly larger in galaxy size and more disk-like compared to field PSBs, which is qualitatively consistent with and thus hints at the environment-driven fast quenching pathway for group PSBs. Taken together, our results support multiple evolutionary pathways for local PSB galaxies: while massive PSBs are thought of as products of fast quenching following a major merger-induced starburst, environment-induced fast quenching should play a role in the evolution of less massive PSBs, especially at M * ≲ 1010 M ☉.

Keywords: galaxy evolution; galaxy structure; galaxy quenching; post-starburst galaxies
Hard X-Ray Observation and Multiwavelength Study of the PeVatron Candidate Pulsar Wind Nebula "Dragonfly"

We studied the PeVatron nature of the pulsar wind nebula (PWN) G75.2+0.1 ("Dragonfly") as part of our NuSTAR observational campaign of energetic PWNe. The Dragonfly is spatially coincident with LHAASO J2018+3651, whose maximum photon energy is 0.27 PeV. We detected a compact (radius $1^{\prime} $ ) inner nebula of the Dragonfly without a spectral break in 3-20 keV using NuSTAR. A joint analysis of the inner nebula with archival Chandra and XMM-Newton (XMM) observations yields a power-law spectrum with Γ = 1.49 ± 0.03. Synchrotron burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies, from which we infer the magnetic field in the inner nebula of 24 μG at 3.5 kpc. Our analysis of archival XMM data and 13 yr of Fermi-LAT data confirms the detection of an extended ( $\sim 10^{\prime} $ ) outer nebula in 2-6 keV (Γ = 1.82 ± 0.03) and the nondetection of a GeV nebula, respectively. Using the VLA, XMM, and HAWC data, we modeled a multiwavelength spectral energy distribution of the Dragonfly as a leptonic PeVatron. The maximum injected particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely a PeVatron. Our model prediction of the low magnetic field (2.7 μG) in the outer nebula and recent interaction with the host supernova remnant's reverse shock (4 kyr ago) align with common features of PeVatron PWNe. The origin of its highly asymmetric morphology, pulsar proper motion, PWN-supernova remnant (SNR) interaction, and source distance will require further investigations in the future, including a multiwavelength study using radio, X-ray, and gamma-ray observations.

Keywords: pulsar wind nebulae; high energy astrophysics; gamma-ray sources; rotation powered pulsars; spectral energy distribution; x-ray sources
Sticking of Fine Particles in High-velocity Impact: Application to Size Distribution of Dust Grains in a Debris Disk

Impact experiments were conducted at a velocity of ~0.2-1.0 km s-1 using fine particles with several microns or submicrons in size. For metal (Cu) plate targets, as observed in previous impact experiments using projectiles with sizes larger than tens of micron, our experiments with the fine particles also show that projectile materials can remain in the crater. For brittle (SiO2 glass) plate targets, though previous impact experiments using projectiles with sizes larger than tens of microns have shown the spallation and ejection of projectile materials, our experiments with the fine particles show that irreversible inelastic deformation of targets occurred and that projectile materials can remain in the crater. This is explained by the absorption of impact energy determined via the competition between deformation and crack propagation. The deformation thus contributes to the energy absorption even for brittle materials at small sizes. Compiling our results and previous data, we found that sticking can occur in collisions with particles up to at least 1 cm for ductile (metal) targets and 10 μm for brittle targets at several hundred meters per second. As an application, we evaluated the size distribution of dust grains in a debris disk where the sticking of fine particles is assumed to occur. We demonstrated that the collisional sticking modified the size distribution, resulting in the decrease of spectral energy distribution at millimeter wavelengths, consistent with the photometry data of this debris disk. This suggests that the sticking of fine particles occurs in this debris disk.

Keywords: planetary science; collisional processes; debris disks
Understanding the Relationship between Solar Coronal Abundances and F10.7 cm Radio Emission

Sun-as-a-star coronal plasma composition, derived from full-Sun spectra, and the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated (r = 0.88) during solar cycle 24. However, this correlation becomes nonlinear during increased solar magnetic activity. Here we use cotemporal, high spatial resolution, multiwavelength images of the Sun to investigate the underlying causes of the nonlinearity between coronal composition (FIP bias) and F10.7 solar index correlation. Using the Karl G. Jansky Very Large Array, Hinode/EIS (EUV Imaging Spectrometer), and the Solar Dynamics Observatory, we observed a small active region, AR 12759, throughout the solar atmosphere from the photosphere to the corona. The results of this study show that the magnetic field strength (flux density) in active regions plays an important role in the variability of coronal abundances, and it is likely the main contributing factor to this nonlinearity during increased solar activity. Coronal abundances above cool sunspots are lower than in dispersed magnetic plage regions. Strong magnetic concentrations are associated with stronger F10.7 cm gyroresonance emission. Considering that as the solar cycle moves from minimum to maximum, the sizes of sunspots and their field strength increase with the gyroresonance component, the distinctly different tendencies of radio emission and coronal abundances in the vicinity of sunspots is the likely cause of saturation of Sun-as-a-star coronal abundances during solar maximum, while the F10.7 index remains well correlated with the sunspot number and other magnetic field proxies.

Keywords: solar corona; solar magnetic fields; solar radio emission; solar abundances
The JCMT SCUBA-2 Survey of the James Webb Space Telescope North Ecliptic Pole Time-Domain Field

The James Webb Space Telescope Time-Domain Field (JWST-TDF) is an ~14' diameter field near the North Ecliptic Pole that will be targeted by one of the JWST Guaranteed Time Observations programs. Here, we describe our James Clerk Maxwell Telescope SCUBA-2 850 μm imaging of the JWST-TDF and present the submillimeter source catalog and properties. We also present a catalog of radio sources from Karl J. Jansky Very Large Array 3 GHz observations of the field. These observations were obtained to aid JWST's study of dust-obscured galaxies that contribute significantly to cosmic star formation at high redshifts. Our deep 850 μm map covers the JWST-TDF at a noise level of σ 850µm = 1.0 mJy beam-1, detecting 83/31 sources in the main/supplementary signal-to-noise ratio (S/N > 4 / S/N = 3.5-4) sample, respectively. The 3 GHz observations cover a 24' diameter field with a 1σ noise of 1 μJy beam-1 at a 0.″7 FWHM. We identified eighty-five 3 GHz counterparts to sixty-six 850 μm sources and then matched these with multiwavelength data from the optical to the mid-infrared wave bands. We performed spectral energy distribution fitting for 61 submillimeter galaxies (SMGs) matched with optical/near-infrared data, and found that SMGs at S/N > 4 have a median value of z phot = 2.22 ± 0.12, star formation rates of 300 ± 40 M ⊙ yr-1 (Chabrier initial mass function), and typical cold dust masses of 5.9 ± 0.7 × 108 M ⊙, in line with bright SMGs from other surveys. The large cold dust masses indicate correspondingly large cool gas masses, which we suggest are a key factor necessary to drive the high star formation rates seen in this population.

Keywords: galaxy evolution; high-redshift galaxies; galaxy formation; submillimeter astronomy; galaxy counts; ultraluminous infrared galaxies
Large-scale Coronal Dimming Foreshadowing a Solar Eruption on 2011 October 1

Understanding large-scale solar eruptions requires detailed investigation of the entire system's evolution, including the magnetic environment enveloping the source region and searches for precursor activity prior to event onset. We combine stereoscopic observations from the Solar Dynamics Observatory (SDO) and STEREO-B spacecraft for several hours before a filament ejection, M1.2-class eruptive flare, and coronal mass ejection (CME) originating in NOAA active region (AR) 11305 on 2011 October 1. Two episodes of significant preeruption coronal dimming that occurred well to the southeast of the ejected filament are identified. The CME subsequently took off with a substantial component of velocity toward the dimming, which became very pronounced during eruption. We used SDO/Helioseismic and Magnetic Imager (HMI) data to reconstruct the magnetic environment of the system and found that it contains a null point near the dimming region. AR 11305 had quite complex connections to nearby ARs 11302 and 11306, as well as to other regions of decayed AR flux. The intensifying and spatially expanding precursor dimming was accompanied by southeastward rising motions of loops toward the null point and northeastward and southwestward motions of loops retracting away. These motions and the dimming are consistent with persistent magnetic reconnection occurring at the null point as it moved upward and southeastward, thereby removing a strapping magnetic field high above AR 11305. Eventually, the filament was ejected explosively toward the null point. We conclude that the breakout model for solar eruptions provides a compelling account of this event. Furthermore, we conjecture that preeruption dimmings may be much more frequent than currently recognized.

Keywords: solar flares; solar coronal mass ejections
Photometric Metallicity Prediction of Fundamental-mode RR Lyrae Stars in the Gaia Optical and K s Infrared Wave Bands by Deep Learning

RR Lyrae stars are useful chemical tracers thanks to the empirical relationship between their heavy-element abundance and the shape of their light curves. However, the consistent and accurate calibration of this relation across multiple photometric wave bands has been lacking. We have devised a new method for the metallicity estimation of fundamental-mode RR Lyrae stars in the Gaia optical G and near-infrared VISTA K s wave bands by deep learning. First, an existing metallicity prediction method is applied to large photometric data sets, which are then used to train long short-term memory recurrent neural networks for the regression of the [Fe/H] to the light curves in other wave bands. This approach allows an unbiased transfer of our accurate, spectroscopically calibrated I-band formula to additional bands at the expense of minimal additional noise. We achieve a low mean absolute error of 0.1 dex and high R 2 regression performance of 0.84 and 0.93 for the K s and G bands, respectively, measured by cross-validation. The resulting predictive models are deployed on the Gaia DR2 and VVV inner bulge RR Lyrae catalogs. We estimate mean metallicities of -1.35 dex for the inner bulge and -1.7 dex for the halo, which are significantly less than the values obtained by earlier photometric prediction methods. Using our results, we establish a public catalog of photometric metallicities of over 60,000 Galactic RR Lyrae stars and provide an all-sky map of the resulting RR Lyrae metallicity distribution. The software code used for training and deploying our recurrent neural networks is made publicly available in the open-source domain.

Keywords: rr lyrae variable stars; metallicity; light curves; neural networks
Catalog of One-side Head-Tail Galaxies in the FIRST Survey

One-side head-tail (OHT) galaxies are radio galaxies with a peculiar shape. They usually appear in galaxy clusters, but they have never been cataloged systematically. We design an automatic procedure to search for them in the Faint Images of the Radio Sky at Twenty-Centimeters source catalog and compile a sample with 115 HT candidates. After cross-checking with the Sloan Digital Sky Survey photometric data and catalogs of galaxy clusters, we find that 69 of them are possible OHT galaxies. Most of them are close to the center of galaxy clusters. The lengths of their tails do not correlate with the projection distance to the center of the nearest galaxy clusters, but show weak anticorrelation with the cluster richness, and are inversely proportional to the radial velocity differences between clusters and host galaxies. Our catalog provides a unique sample to study this special type of radio galaxies.

Keywords: tailed radio galaxies; galaxy clusters; galaxy infall
The Redshift Evolution of the Binary Black Hole Mass Distribution from Dense Star Clusters

Gravitational-wave detectors are unveiling a population of binary black hole (BBH) mergers out to redshifts z ≈ 1, and are starting to constrain how the BBH population evolves with redshift. We present predictions for the redshift evolution of the BBH mass and spin distributions for systems originating from dense star clusters. Utilizing a grid of 144 state-of-the-art dynamical models for globular clusters, we demonstrate that BBH merger rates peak at higher redshifts for larger black hole primary masses M 1. Specifically, for M 1 ≳ 40 M ⊙, the BBH merger rate reaches its peak at redshift z ≈ 2.1, while for M 1 ≲ 20 M ⊙, the peak occurs at z ≈ 1.1, assuming that the cluster formation rate peaks at z = 2.2. The average BBH primary mass also increases from ∼10 M ⊙ at z = 0 to ∼30 M ⊙ at z = 10. We show that ∼20% BBHs contain massive remnants from next-generation mergers, with this fraction increasing (decreasing) for larger (smaller) primary masses. This difference is not large enough to significantly alter the effective spins of the BBH population originating from globular clusters, and we find that their effective spin distribution does not evolve across cosmic time. These findings can be used to distinguish BBHs from dense star clusters by future gravitational-wave observations.

Keywords: black holes; gravitational waves; globular star clusters
Spatially Resolved Recent Star Formation History in NGC 6946

The nearby face-on star-forming spiral galaxy NGC 6946 is known as the Fireworks Galaxy due to its hosting an unusually large number of supernovae. We analyze its resolved near-ultraviolet stellar photometry measured from images taken with the Hubble Space Telescope's Wide Field Camera 3 with the F275W and F336W filters. We model the color-magnitude diagrams of the UV photometry to derive the spatially resolved star formation history of NGC 6946 over the last 25 Myr. From this analysis, we produce maps of the spatial distribution of the young stellar population and measure the total recent star formation rate (SFR) of nearly the entire young stellar disk. We find the global SFR(age ≤25 Myr) = ${13.17}_{-0.79}^{+0.91}{M}_{\odot }\,{\mathrm{yr}}^{-1}$ . Over this period, the SFR is initially very high ( ${23.39}_{-2.11}^{+2.43}{M}_{\odot }\,{\mathrm{yr}}^{-1}$ 16-25 Myr ago), then monotonically decreases to ${5.31}_{-0.17}^{+0.19}{M}_{\odot }\,{\mathrm{yr}}^{-1}$ in the last 10 Myr. This decrease in global SFR over the last 25 Myr is consistent with measurements made with other SFR indicators. We discuss in detail two of the most active regions of the galaxy, which we find are responsible for 3% and 5% of the total star formation over the past 6.3 Myr.

Keywords: star formation; spiral galaxies; galaxy evolution; stellar populations
Testing the Speed of Light Variation with Strong Gravitational Lensing of SNe 1a

The constancy of the speed of light c is the foundation of most physical theories and is found to be indeed constant from local measurements. Whether or not the same is true at cosmological timescale has been of interest for some time. The measurement of time delay difference in the peaking of the luminosity between two gravitationally lensed images of a type 1a-supernova has recently been proposed to determine if c was different from its current value at the time the images were produced by a lensing galaxy. Since the geometrical time delay and the Shapiro time delay both scale as G/c3 we show that this method of constraining c is valid only when the potential variation of the gravitational constant G is ignored: c variation is imperceptible when G ~ c3.

Keywords: cosmology; dirac cosmology; cosmological models
The Role of Pickup Ions in the Interaction of the Solar Wind with the Local Interstellar Medium. I. Importance of Kinetic Processes at the Heliospheric Termination Shock

The role of pickup ions (PUIs) in the solar wind interaction with the local interstellar medium is investigated with 3D, multifluid simulations. The flow of the mixture of all charged particles is described by the ideal MHD equations, with the source terms responsible for charge exchange between ions and neutral atoms. The thermodynamically distinct populations of neutrals are governed by individual sets of gas dynamics Euler equations. PUIs are treated as a separate, comoving fluid. Because the anisotropic behavior of PUIs at the heliospheric termination shocks is not described by the standard conservation laws (a.k.a. the Rankine-Hugoniot relations), we derived boundary conditions for them, which are obtained from the dedicated kinetic simulations of collisionless shocks. It is demonstrated that this approach to treating PUIs makes the computation results more consistent with observational data. In particular, the PUI pressure in the inner heliosheath (IHS) becomes higher by ~40%-50% in the new model, as compared with the solutions where no special boundary conditions are applied. Hotter PUIs eventually lead to charge-exchange-driven cooling of the IHS plasma, which reduces the IHS width by ~15% (~8-10 au) in the upwind direction, and even more in the other directions. The density of secondary neutral atoms born in the IHS decreases by ~30%, while their temperature increases by ~60%. Simulation results are validated with New Horizons data at distances between 11 and 47 au.

Keywords: heliosphere; solar wind; interstellar medium; pickup ions; termination shock; magnetohydrodynamics; space plasmas; charge exchange ionization
Thermodynamics of the Inner Heliosheath

We derive annual sky maps of the proton temperature in the inner heliosheath (IHS), and track their temporal evolution over the years 2009-2016 of Interstellar Boundary Explorer observations. Other associated thermodynamic parameters also determined are the density, kappa (the parameter that characterizes kappa distributions), temperature rate, polytropic index, and entropy. We exploit the theory of kappa distributions and their connection with polytropes, to (i) express a new polytropic quantity Π that remains invariant along streamlines where temperature and density may vary, (ii) parameterize the proton flux in terms of the Π invariant and kappa, and (iii) derive the temperature and density, respectively, from the slope and intercept of the linear relationship between kappa and logarithm of Π. We find the following thermodynamic characteristics: (1) temperature sky maps and histograms shifted to their lowest values in 2012 and their highest in 2015; (2) temperature negatively correlated with density, reflecting the subisothermal polytropic behavior; (3) temperature positively correlated with kappa, revealing characteristics of the mechanism responsible for generating kappa distributions; (4) processes in IHS are subisothermal tending toward isobaric, consistent with previously published results; (5) linear relationship between kappa and polytropic indices, revealing characteristics of the particle potential energy; and (6) entropy positively correlated with polytropic index, aligned with the underlying theory that entropy increases toward the isothermal state where the kappa distribution reduces to the Maxwell-Boltzmann description.

Keywords: space plasmas; heliosheath; heliosphere
AGNs Are Not That Cool: Revisiting the Intrinsic AGN Far-infrared Spectral Energy Distribution

We investigate the intrinsic spectral energy distribution (SED) of active galactic nuclei (AGNs) at infrared (IR) bands with 42 z < 0.5 optically luminous Palomar Green survey quasars through SED decomposition. We decompose the SEDs of the 42 quasars by combining an AGN IR template library that covers a wide range of the AGN parameter space with three commonly used galaxy template libraries. We determine the median AGN SED from the best-fitting results. The far-IR (FIR) contribution of our median AGN SED is significantly smaller than that of Symeonidis et al., but roughly consistent with that of Lyu & Rieke. The AGN IR SED becomes cooler with increasing bolometric luminosity, which might be due to the fact that more luminous AGNs might have stronger radiative feedback to change torus structures and/or their tori might have higher metallicities. Our conclusions do not depend on the choice of galaxy template libraries. However, as the predicted polycyclic aromatic hydrocarbon (PAH) emission line flux is galaxy template dependent, cautions should be taken on deriving galaxy FIR contribution from PAH fluxes.

Keywords: infrared galaxies; active galactic nuclei; spectral energy distribution; supermassive black holes
The Formation of C3O3H6 Structural Isomers in the Gas Phase through Barrierless Pathways: Formation and Spectroscopic Characterization of Methoxy Acetic Acid

Gas phase formation processes feasible at low temperatures are determined theoretically for 38 isomers obeying the C3O3H6 empirical formula, one of them, the simplest ketose dihydroxyacetone, has been observed in gas phase sources. A preliminary search for isomeric forms first targets ethoxy formic acid (C2H5-O-COOH) as the most stable isomer followed by lactic acid. Profiles corresponding to the minimum energy pathways reveal that the favored conformers of 14 of these isomers can be formed in the gas phase through 29 barrierless processes involving the OH*, CH3O*, HCO*, CH3*, CH2OH, HCOO*, and OHCO* radicals, all of them observed in the interstellar medium. Kinetic rates are provided at 200, 298, and 500 K, confirming the suitability of 16 processes at low temperatures. Faster processes involve the OH hydroxyl radical whereas, to a lesser degree, the processes involving the HOCO radical and the methoxy methyl radical CH3O*, are quite significant. Spectroscopic parameters (rovibrational and torsional) are obtained for methoxy acetic acid (CH3-O-CH2COOH) for which two low-lying isoenergetic conformers can be produced from the CH3OCH2* radical predicted to be a precursor of abundant observed molecules. Profiles and spectroscopic properties make methoxy acetic acid a good candidate to be detected in the gas phase of extraterrestrial sources.

Keywords: molecular physics; molecule formation; molecular spectroscopy