adsabs/SciX_UAT_keywords huggingface dataset:
Morphology of Galaxies in JWST Fields: Initial Distribution and Evolution of Galaxy Morphology

A recent study from the Horizon Run 5 (HR5) cosmological simulation has predicted that galaxies with $\mathrm{log}\,{M}_{* }/{M}_{\odot }\lesssim 10$ in the cosmic morning (10 ≳ z ≳ 4) dominantly have disk-like morphology in the ΛCDM universe, which is driven by the tidal torque in the initial fluctuations of matter. For a direct comparison with observation we identify a total of about 19,000 James Webb Space Telescope (JWST) galaxies with $\mathrm{log}\,{M}_{* }/{M}_{\odot }\gt 9$ at z = 0.6–8.0 utilizing deep JWST/NIRCam images of publicly released fields, including North Ecliptic Pole Time-Domain Fields, Next Generation Deep Extragalactic Exploratory Public survey, Cosmic Evolution Early Release Science Survey, Cosmic Evolution Survey, UltraDeep Survey, and SMACS J0723-7327. We estimate their stellar masses and photometric redshifts with the redshift dispersion of σ NMAD = 0.009 and an outlier fraction of only about 6%. We classify galaxies into three morphological types, disks, spheroids, and irregulars, applying the same criteria used in the HR5 study. The morphological distribution of the JWST galaxies shows that disk galaxies account for 60%–70% at all redshift ranges. However, in the high-mass regime ( $\mathrm{log}\,{M}_{* }/{M}_{\odot }\gtrsim 11$ ), spheroidal morphology becomes the dominant type. This implies that the mass growth of galaxies is accompanied by a morphological transition from disks to spheroids. The fraction of irregulars is about 20% or less at all masses and redshifts. All the trends in the morphology distribution are consistently found in the six JWST fields. These results are in close agreement with the results from the HR5 simulation, particularly confirming the prevalence of disk galaxies at small masses in the cosmic morning and noon.

Keywords: galaxy evolution; galaxy classification systems
Reconnection along a Separator in Shock Turbulence

Numerous structures conducive to magnetic reconnection are frequently observed in the turbulent regions at quasi-parallel shocks. In this work, we use a particle-in-cell simulation to study 3D magnetic reconnection in shock turbulence. We identify and characterize magnetic null points, and focus on reconnection along the separator between them. We identify a reconnection region with strong parallel current, a finite parallel potential, and counterrotating electron flows. Electrons are shown to be accelerated by the parallel electric field before being scattered at the null.

Keywords: planetary bow shocks; plasma physics; space plasmas
Quiet-Sun Mg II h and k Line Profiles Derived from IRIS Full-Sun Mosaics. I. Reference Profiles and Center-to-limb Variation

We derived high-precision reference profiles of the Mg II h and k lines that represent the quiet Sun during a minimum of the solar activity. To do so, we used the broad catalog of full-Sun mosaics obtained by the Interface Region Imaging Spectrograph (IRIS). To minimize the influence of the local variations due to the on-disk solar features and to achieve low levels of uncertainties, we used 12 IRIS full-Sun mosaics without sunspots or other significant signs of solar activity. These mosaics were obtained between 2019 April and 2020 September in the near-ultraviolet spectral range. In this paper, we present the disk-averaged reference profiles of Mg II h and Mg II k lines, together with a series of reference profiles spanning the distance between the disk center and the solar limb. These series of profiles offer a detailed representation of the center-to-limb variation of both Mg II h and Mg II k lines. The reference Mg II h and k line profiles provided in this paper can be used as the incident radiation boundary condition for radiative-transfer modeling of prominences, spicules, and other coronal and chromospheric structures.

Keywords: solar ultraviolet emission; solar atmosphere; limb darkening; limb brightening; solar spectral irradiance
Circumbinary Disk Accretion into Spinning Black Hole Binaries

Supermassive black hole binaries are likely to accrete interstellar gas through a circumbinary disk. Shortly before merger, the inner portions of this circumbinary disk are subject to general relativistic effects. To study this regime, we approximate the spacetime metric of close orbiting black holes by superimposing two boosted Kerr-Schild terms. After demonstrating the quality of this approximation, we carry out very long-term general relativistic magnetohydrodynamic simulations of the circumbinary disk. We consider black holes with spin dimensionless parameters of magnitude 0.9, in one simulation parallel to the orbital angular momentum of the binary, but in another anti-parallel. These are contrasted with spinless simulations. We find that, for a fixed surface mass density in the inner circumbinary disk, aligned spins of this magnitude approximately reduce the mass accretion rate by 14% and counter-aligned spins increase it by 45%, leaving many other disk properties unchanged.

Keywords: accretion; supermassive black holes; rotating black holes; magnetohydrodynamical simulations
The Origin of the Large Magellanic Cloud Globular Cluster NGC 2005

The ancient Large Magellanic Cloud (LMC) globular cluster NGC 2005 has recently been reported to have an ex situ origin, thus, setting precedents that the LMC could have partially formed from smaller merged dwarf galaxies. We here provide additional arguments from which we conclude that is also fairly plausible an in situ origin of NGC 2005, based on the abundance spread of a variety of chemical elements measured in dwarf galaxies, their minimum mass in order to form globular clusters, the globular cluster formation imprints kept in their kinematics, and the recent modeling showing that explosions of supernovae are responsible for the observed chemical abundance spread in dwarf galaxies. The present analysis points to the need for further development of numerical simulations and observational indices that can help us to differentiate between two mechanisms of galaxy formation for the LMC; namely, a primordial dwarf or an initial merging event of smaller dwarfs.

Keywords: large magellanic cloud; globular star clusters
Coronal Electron Temperature Inferred from the Strahl Electrons in the Inner Heliosphere: Parker Solar Probe and Helios Observations

The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modeled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analyzed the data obtained by two missions, Helios, spanning the distances between 65 and 215 RS, and Parker Solar Probe (PSP), reaching down to 35 RS during its first two orbits around the Sun. The electron strahl was characterized with two parameters: pitch-angle width (PAW) and the strahl parallel temperature (Ts∥). PSP observations confirm the already reported dependence of strahl PAW on core parallel plasma beta (βec\parallel). Most of the strahl measured by PSP appear narrow with PAW reaching down to 30°. The portion of the strahl velocity distribution function aligned with the magnetic field is for the measured energy range well described by a Maxwellian distribution function. Ts∥ was found to be anticorrelated with the solar wind velocity and independent of radial distance. These observations imply that Ts∥ carries the information about the coronal electron temperature. The obtained values are in agreement with coronal temperatures measured using spectroscopy, and the inferred solar wind source regions during the first orbit of PSP agree with the predictions using a PFSS model.

Keywords: solar wind; solar physics; space plasmas; space vehicle instruments; astronomy data analysis; solar corona; solar atmosphere
Formation of Massive Black Holes with M = (103-108) M ⊙ at Pre-quasar Epochs through Hoyle-Lyttleton-Bondi Accretion of Self-interacting Dark Matter onto a Moving Seed

The presence of supermassive black holes with M ~ 109 M ⊙ hosted by the luminous quasars at cosmological redshift z ≥ 6 is still an open problem in astrophysical cosmology. Here we study the formation of massive black holes at high redshift (z ≫ 7) through Hoyle-Lyttleton-Bondi accretion of self-interacting dark matter (SIDM) onto a 20 M ⊙ seed black hole moving with a velocity ~100 km s-1 inside the short, mean-free path region of an SIDM halo. We consider observational constraints on a specific SIDM cross section, σ/m dm = (0.1-5) cm2 g-1. Formation timescale of massive black holes with M = (103-108) M ⊙ is calculated for the universal Navarro-Frenk-White (NFW) profile, singular isothermal sphere (SIS), other power-law profiles with a cusp index 2.19 ≤ γ ≤ 2.5 of accreted dark matter, and modified-core isothermal profiles. The ambient sound speed is taken as C s = (10-100) km s-1. It is found that an NFW profile with halo concentration C = 4.75-32.58 estimated at z = 20 and 30 for halo masses M 200 = (1012-1014) M ⊙ favors formation of massive black holes with M = (103-108) M ⊙ at high redshift, well before quasar epoch. In this profile, these black holes grow within timescales (0.1-69) Myr at z = 16-20. For the SIS profile, the black hole formation timescales are short compared to NFW. For power-law profiles, massive black holes with M = (106-108) M ⊙ grow within a few tens to 100 Myr (z = 5-30). For modified-core isothermal profiles, the timescale of massive black hole formation is in the range (0.79-464.08) Myr (z = 8-30).

Keywords: supermassive black holes; dark matter; bondi accretion
X-Ray Intraday Variability of the TeV Blazar Markarian 421 with XMM-Newton

Highly variable Markarian 421 is a bright high-synchrotron energy peaked blazar showing a wide featureless nonthermal spectrum, making it a good candidate for our study of intraday flux and spectral variations over time. We analyze its X-ray observations over 17 yr, taken with the EPIC-pn instrument, to probe into the intraday variability properties, focusing on the photon energy band of 0.3-10.0 keV, and its soft (0.3-2.0 keV) and hard (2.0-10.0 keV) subbands. To examine the flux variability, fractional variability amplitudes and minimum variability timescales have been calculated. We also probed into the spectral variability by studying the hardness ratio for each observation, the correlation between the two energy bands, using the discrete correlation function, and inspecting the normalized light curves. The parameters obtained from these methods were studied for any correlations or nonrandom trends. From this work, we speculate on the constraints on the possible particle acceleration and emission processes in the jet, for a better understanding of the processes involving turbulent behavior, except for shocks. A positive discrete correlation function between the two subbands indicates the role of the same electron population in the emission of photons in the two bands. A correlation between the parameter of flux variability and the parameters of spectral variation and lags in the subenergy bands provides the constraints to be considered for any modeling of emission processes.

Keywords: active galactic nuclei; blazars; x-ray astronomy; hardness ratio; active galaxies
An XMM-Newton View of the Andromeda Galaxy as Explored in a Legacy Survey (New-ANGELS). I. The X-Ray Source Catalog

We introduce the New-ANGELS program, an XMM-Newton survey of a ~7.2 deg2 area around M31, which aims to study the X-ray populations in the M31 disk and the X-ray-emitting hot gas in the inner halo of M31 up to 30 kpc. In this first paper, we report the catalog of 4506 detected X-ray sources and attempt to cross-identify or roughly classify them. We identify 352 single stars in the foreground, 35 globular clusters, and 27 supernova remnants associated with M31, as well as 62 active galactic nuclei, 59 galaxies, and one galaxy cluster in the background. We uniquely classify 236 foreground stars and 17 supersoft sources based on their X-ray colors. X-ray binaries (83 low-mass and one high-mass) are classified based on their X-ray colors and X-ray variabilities. The remaining X-ray sources either have too low signal-to-noise ratios to calculate their X-ray colors or do not have a unique classification, so are regarded as unclassified. The X-ray source catalog is published online. Studies of the X-ray source populations and the contribution of X-ray sources in the unresolved X-ray emissions based on this catalog will be published in companion papers.

Keywords: x-ray identification; x-ray sources; andromeda galaxy; stellar populations
Modeling Light Curves of Bipolar Core Collapse Supernovae from the Equatorial Plane

We use the two-components bipolar toy model of core collapse supernova (CCSN) ejecta to fit the rapid decline from maximum luminosity in the light curve of the type IIb CCSN SN 2018gk (ASASSN-18am). In this toy model we use a template light curve from a different CCSN that is similar to SN 2018gk, but that has no rapid drop in its light curve. The bipolar morphology that we model with a polar ejecta and an equatorial ejecta increases the maximum luminosity and causes a steeper decline for an equatorial observer, relative to a similar spherical explosion. The total energy and mass of our toy model for SN 2018gk are ${E}_{\mathrm{SN}}=5\times {10}^{51}\,\mathrm{erg}$ and ${M}_{\mathrm{SN}}=2.7{M}_{\odot }$ . This explosion energy is more than what a neutrino driven explosion mechanism can supply, implying that jets exploded SN 2018gk. These energetic jets likely shaped the ejecta to a bipolar morphology, as our toy model requires. We crudely estimate that f ≈ 2%-5% of all CCSNe show this behavior, most being hydrogen deficient (stripped-envelope) CCSNe, as we observe them from the equatorial plane. We estimate the overall fraction of CCSNe that have a pronounced bipolar morphology to be fbip ≈ 5%-15% of all CCSNe.

Keywords: supernovae; stellar jets
The Evolution of the Optical Spectrum of V455 Andromedae throughout the 2007 Superoutburst

V455 And is a dwarf nova with a short orbital period, close to the orbital period minimum. The object underwent its first detected outburst in 2007, brightening from around V = 16.5 all the way to magnitude 8. Outbursts of such amplitude occur exclusively in dwarf novae with short periods (typically P orb ≲ 90 minutes) and are called superoutbursts. The recurrence time of superoutbursts is long (decades), hence only very few have been studied in detail. We succeeded in observing the entire superoutburst of V455 And spectroscopically from the rise to the decline with unprecedented detail. While the light curve of the object throughout the outburst does not seem to differ much from other dwarf novae, its spectroscopic behavior is strikingly different during the transition stage from the absorption-dominated lines to the strong emission one during the rise. We interpret the emergence of the strong emission lines with little radial velocity variations during the superoutburst as evidence of wind from the evaporating disk in this high-inclination system. The evolution of the line profiles from wide to narrow peak separation during the rise, and back at the decline, matches models showing that the peak separation is a function of optical depth in the lines.

Keywords: cataclysmic variable stars
Investigating Overdensities around z > 6 Galaxies through ALMA Observations of [C II]

We present a search for companion [C II] emitters to known luminous sources at 6 < z < 6.5 in deep, archival ALMA observations. The observations are deep enough to detect sources with ${L}_{[{\rm{C}}{\rm{II}}]}\sim {10}^{8}\ {L}_{\odot }$ at z ∼ 6. We identify three new robust line detections from a blind search of five deep fields centered on ultraluminous infrared galaxies and QSOs. We calculate the volume density of companions and find a relative overdensity of ${6}_{-3}^{+4}$ and ${86}_{-37}^{+60}$ when comparing to current observational constraints and theoretical predictions, respectively. These results suggest that the central sources may be highly biased tracers of mass in the early universe. We find these companion lines to have comparable properties to other known galaxies at the same epoch. All companions lie less than 650 km s-1 and between 25 and 60 kpc (projected) from their central source. To place these discoveries in context, we employ a mock galaxy catalog to estimate the luminosity function for [C II] during reionization and compare to our observations. The simulations support this result by showing a similar level of elevated counts found around such luminous [C II] sources.

Keywords: quasar-galaxy pairs; reionization; submillimeter astronomy; high-redshift galaxies; galaxies
Molecular Clouds as Gravitational Instabilities in Rotating Disks: A Modified Stability Criterion

Molecular gas disks are generally Toomre stable (Q T > 1) and yet clearly gravitationally unstable to structure formation as evidenced by the existence of molecular clouds and ongoing star formation. This paper adopts a 3D perspective to obtain a general picture of instabilities in flattened rotating disks, using the 3D dispersion relation to describe how disks evolve when perturbed over their vertical extents. By explicitly adding a vertical perturbation to an unperturbed equilibrium disk, stability is shown to vary with height above the midplane. Near z = 0, where the equilibrium density is roughly constant, instability takes on a Jeans-like quality, occurring on scales larger than the Jeans length and subject to a threshold Q M = κ 2/(4π G ρ) = 1 or roughly Q T ≈ 2. Far from the midplane, on the other hand, stability is pervasive, and the threshold for the total disk (out to z = ±∞) to be stabilized is lowered to Q T = 1 as a consequence. In this new framework, gas disks are able to fragment through partial 3D instability even where total 2D instability is suppressed. The growth rates of the fragments formed via 3D instability are comparable to, or faster than, Toomre instabilities. The rich structure in molecular disks on the scale of tens of parsecs can thus be viewed as a natural consequence of their 3D nature and their exposure to a variety of vertical perturbations acting on roughly a disk scale height, i.e., due to their situation within the more extended galaxy potential, participation in the disk-halo flow, and exposure to star formation feedback.

Keywords: disk galaxies; galaxy dynamics; interstellar medium; giant molecular clouds
Numerical Performance of Correlated-k Distribution Method in Atmospheric Escape Simulation

Atmospheric escape is crucial to understanding the evolution of planets in and out of the solar system and to interpreting atmospheric observations. While hydrodynamic escape simulations have been actively developed incorporating detailed processes such as UV heating, chemical reactions, and radiative cooling, the radiative cooling by molecules has been treated as emission from selected lines or rotational/vibrational bands to reduce its numerical cost. However, ad hoc selections of radiative lines would risk estimating inaccurate cooling rates because important lines or wavelengths for atmospheric cooling depend on emitting conditions such as temperature and optical thickness. In this study, we apply the correlated-k distribution (CKD) method to cooling rate calculations for H2-dominant transonic atmospheres containing H2O or CO as radiative species, to investigate its numerical performance and the importance of considering all lines of the molecules. Our simulations demonstrate that the sum of weak lines, which provides only 1% of the line emission energy in total at optically thin conditions, can become the primary source of radiative cooling in optically thick regions, especially for H2O-containing atmospheres. Also, in our hydrodynamic simulations, the CKD method with a wavelength resolution of 1000 is found to be effective, allowing the calculation of escape rate and temperature profiles with acceptable numerical cost. Our results show the importance of treating all radiative lines and the usefulness of the CKD method in hydrodynamic escape simulations. It is particularly practical for heavy-element-enriched atmospheres considered in small exoplanets, including super-Earths, without any prior selections for effective lines.

Keywords: exoplanet atmospheric evolution; exoplanet atmospheres; upper atmosphere
An Optical Overview of Blazars with LAMOST. I. Hunting Changing-look Blazars and New Redshift Estimates

The extragalactic γ-rays sky observed by the Fermi Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi LAT Point Source Catalog (4FGL) are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature, known as blazar candidates of uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carry out an extensive search for optical spectra available in the Large Sky Area Multi-object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We select sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated γ-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We select a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classify 20 BCUs confirming their blazar-like nature. Then we obtain 15 new redshift estimates for known blazars. We discover 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we are able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the γ-ray extragalactic sky.

Keywords: optical identification; blazars; bl lacertae objects; flat-spectrum radio quasars
Multiwavelength Photometry and Progenitor Analysis of the Nova V906 Car

We present optical and infrared photometry of the classical nova V906 Car, also known as Nova Car 2018 and ASASSN-18fv, which was discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) on 2018 March 16.32 UT (MJD 58193.0). The nova reached its maximum on MJD 58222.56 at Vmax = 5.84 ± 0.09 mag, and had decline times of ${t}_{2,V}=26.2$ days and ${t}_{3,V}=33.0$ days. The data from Evryscope shows that the nova had already brightened to $g^{\prime} \simeq 13$ mag five days before discovery, as compared with its quiescent magnitude of g = 20.13 ± 0.03. The extinction toward the nova, as derived from high-resolution spectroscopy, shows an estimate consistent with foreground extinction to the Carina Nebula of ${A}_{V}={1.11}_{-0.39}^{+0.54}$. The light curve resembles a rare C (cusp) class nova with a steep decline slope of α = -3.94 post-cusp flare. From the light-curve decline rate, we estimate the mass of the white dwarf to be MWD = <0.8M⊙, consistent with ${M}_{\mathrm{WD}}={0.71}_{-0.19}^{+0.23}$ derived from modeling the accretion disk of the system in quiescence. The donor star is likely a K-M dwarf of 0.23-0.43 ${M}_{\odot }$, which is heated by its companion.

Keywords: classical novae; extinction; photometry