Sazuna/UAT_keywords huggingface dataset:
Gravitational Potential and Surface Density Drive Stellar Populations. II. Star-forming Galaxies. Stellar population parameters correlate with a range of galaxy properties, but it is unclear which relations are causal and which are the result of another underlying trend. In this series, we quantitatively compare trends between stellar population properties and galaxy structural parameters in order to determine which relations are intrinsically tighter, and are therefore more likely to reflect a causal relation. Specifically, we focus on the galaxy structural parameters of mass M, gravitational potential ${\rm{\Phi }}\sim M/{R}_{e}$ , and surface mass density ${\rm{\Sigma }}\sim M/{R}_{e}^{2}$ . In Barone et al. we found that for early-type galaxies (ETGs) the age-Σ and [Z/H]-Φ relations show the least intrinsic scatter as well as the least residual trend with galaxy size. In this work we study the ages and metallicities measured from full spectral fitting of 2085 star-forming galaxies (SFGs) from the SDSS Legacy Survey, selected so all galaxies in the sample are probed to one effective radius. As with the trends found in ETGs, we find that in SFGs age correlates best with stellar surface mass density, and [Z/H] correlates best with gravitational potential. We discuss multiple mechanisms that could lead to these scaling relations. For the [Z/H]-Φ relation we conclude that gravitational potential is the primary regulator of metallicity, via its relation to the gas escape velocity. The age-Σ relation is consistent with compact galaxies forming earlier, as higher gas fractions in the early universe cause old galaxies to form more compactly during their in situ formation phase, and may be reinforced by compactness-related quenching mechanisms.

Keywords: Galaxy stellar content, Scaling relations, Galaxy ages, Galaxy abundances, Extragalactic astronomy
Revisiting the Sołtan Argument Based on a Semianalytical Model for Galaxy and Black Hole Evolution. We show the significance of the super-Eddington accretion for the cosmic growth of supermassive black holes (SMBHs) with a semianalytical model for galaxy and black hole evolution. The model explains various observed properties of galaxies and active galactic nuclei at a wide redshift range. By tracing the growth history of individual SMBHs, we find that the fraction of the SMBH mass acquired during the super-Eddington accretion phases to the total SMBH mass becomes larger for less massive black holes and at higher redshift. Even at z ∼ 0, SMBHs with $\gt {10}^{9}{M}_{\odot }$ have acquired more than 50% of their mass by super-Eddington accretions, which is apparently inconsistent with the classical Sołtan argument. However, the mass-weighted radiation efficiency of SMBHs with $\gt {10}^{8}{M}_{\odot }$ obtained with our model, is about 0.08 at z ∼ 0, which is consistent with Sołtan's argument within the observational uncertainties. We, therefore, conclude that Sołtan's argument cannot reject the possibility that SMBHs are grown mainly by super-Eddington accretions.

Keywords: Supermassive black holes, Galaxy formation, Active galactic nuclei
Hot Subdwarf Stars Identified in Gaia DR2 with Spectra of LAMOST DR6 and DR7. II.Kinematics. Combining LAMOST radial velocities with Gaia parallaxes and proper motions, we present 3D Galactic space motions and the orbits of 182 single-lined hot subdwarf stars. These stars were identified by Lei et al. in Gaia DR2 with LAMOST DR6 and DR7 spectra. He-rich hot subdwarf stars with $\mathrm{log}(y)\geqslant 0$ show the largest standard deviations of the Galactic velocity components and orbital parameters, while those with $-1\leqslant \mathrm{log}(y)\lt 0$ exhibit the second largest standard deviations. The two groups of He-deficient stars with $\mathrm{log}(y)\lt -1$ show similar standard deviations, which are systematically lower compared to He-rich stars. We also present a kinematic population classification of the four hot subdwarf helium groups based on their positions in the U - V velocity diagram, the ${J}_{Z}-$ eccentricity diagram, and their Galactic orbits. The overall tendency of the fractional distributions of the four hot subdwarf helium groups in the halo, thin disk, and thick disk is largely consistent with the findings reported by Luo et al. based on LAMOST DR5, which appears to support predictions of binary population synthesis. He-deficient stars with $-2.2\leqslant \mathrm{log}(y)\lt -1$ likely originate from a stable Roche lobe overflow channel, He-deficient stars with $\mathrm{log}(y)\lt -2.2$ from the common envelope ejection channel, and He-rich stars with $\mathrm{log}(y)\geqslant 0$ from the merger channel of double He white dwarf stars. The fraction of He-rich hot subdwarf stars with $-1\leqslant \mathrm{log}(y)\lt 0$ in the thin disk and the halo is far higher than that in the thick disk, which implies that these stars have different formation channels in the thin disk and in the halo.

Keywords: Stellar kinematics, Subdwarf stars
Advancing the Velocity Gradient Technique: Using Gradient Amplitudes and Handling Thermal Broadening. The recent development of the velocity gradient technique allows observers to map magnetic field orientations and magnetization using the direction of velocity gradients. Aside from the directions, amplitudes of velocity gradients also contain valuable information about the underlying properties of magnetohydrodynamic (MHD) turbulence. In this paper, we explore what physical information is contained in the amplitudes of velocity gradients and discuss how this information can be used to diagnose properties of turbulence in both diffuse and self-gravitating interstellar media. We identify the relations between amplitudes of both intensity and velocity centroid gradients and the sonic Mach number Ms, and they are consistent with the theory's predictions. We test the robustness of the method and discuss how to utilize the amplitudes of gradients into self-gravitating media. To extend the velocity gradient technique, we also discuss the usage of amplitude method to position-position-velocity space as a possible way to retrieve the velocity channel maps before the contamination of thermal broadening. We discuss that the velocity gradient technique with these advancements could potentially give a significantly more accurate statistical insight into the properties of magnetized turbulence.

Keywords: Interstellar magnetic fields, Interstellar dynamics, Interstellar medium
Curvature of Magnetic Field Lines in Compressible Magnetized Turbulence: Statistics, Magnetization Predictions, Gradient Curvature, Modes, and Self-gravitating Media. Magnetic field lines in interstellar media have a rich morphology, which could be characterized by geometrical parameters such as curvature and torsion. In this paper we explore the statistical properties of magnetic field line curvature κ in compressible magnetized turbulence. We see that both the mean and standard deviation of magnetic field line curvature obey power-law relations to the magnetization. Moreover, the power-law tail of the curvature probability distribution function is also proportional to the Alfvénic Mach number. We also explore whether the curvature method could be used in the field-tracing velocity gradient technique. In particular, we observe that there is a relation between the mean and standard deviation of the curvature probed by velocity gradients to MA. Finally, we discuss how curvature is contributed by different MHD modes in interstellar turbulence and suggests that the eigenvectors of MHD modes could be possibly represented by the natural Frenet-Serret frame of the magnetic field lines. We discuss possible theoretical and observational applications of the curvature technique, including the extended understanding on a special length scale that characterizes the importance of magnetic field curvature in driving MHD turbulence, and how it could be potentially used to study a self-gravitating system.

Keywords: Interstellar magnetic fields, Interstellar dynamics, Interstellar medium
The Drag Instability in a 1D Isothermal C-shock. We investigate whether the drag instability, proposed by Gu et al., occurs in a one-dimensional (1D) C-shock. The 1D background model proposed by Chen &amp; Ostriker for a steady isothermal C-shock is adopted, and a 1D isothermal linear analysis is performed. We confirm the postulation of Gu et al. that the drift velocity between ions and neutrals is sufficiently high within a C-shock to allow for the drag instability. We also study the underlying physics of the decaying modes in the shock and postshock regions. The drag instability is an overstability phenomenon associated with an exponentially growing mode of a propagating wave. We find that the growing wave mode can only propagate downstream within the shock and subsequently decay in the postshock region. The maximum total growth for such an unstable wave before it is damped is estimated in typical environments of star-forming clouds, which is approximately 10-30 times larger than the initial perturbation at the modest shock velocities and can be significantly enhanced several hundred times for a stronger C-shock with a larger width.

Keywords: Star forming regions, Plasma astrophysics, Molecular clouds, Interstellar magnetic fields, Interstellar clouds, Shocks
Properties of the KISS Green Pea Galaxies. Green peas (GPs) are a class of extreme star-forming galaxies (SFGs) at intermediate redshifts, originally discovered via color selection using multifilter, wide-field survey imaging data. They are commonly thought of as being analogs of high-redshift Lyα-emitting galaxies. The defining characteristic of GP galaxies is a high-excitation nebular spectrum with very large equivalent width lines, leading to the recognition that GP-like galaxies can also be identified in samples of emission-line galaxies. Here we compare the properties a sample of [O III]-selected SFGs (z = 0.29-0.41) from the KPNO International Spectroscopic Survey (KISS) with the color-selected GPs. We find that the KISS [O III]-selected galaxies overlap with the parameter space defined by the color-selected GPs; the two samples appear to be drawn from the same population of objects. We compare the KISS GPs with the full Hα-selected KISS SFG sample (z &lt; 0.1) and find that they are extreme systems. Many appear to be young systems at their observed look-back times (3-4 Gyr), with more than 90% of their rest-frame B-band luminosity coming from the starburst population. We compute the volume density of the KISS red (KISSR) GPs at z = 0.29-0.41 and find that they are extremely rare objects. We do not see galaxies as extreme as the KISSR GPs in the local universe, although we recognize several lower-luminosity systems at z &lt; 0.1.

Keywords: Starburst galaxies, Emission line galaxies, Galaxy abundances, Star formation, Galaxy evolution
Tests of Conservation Laws in Post-Newtonian Gravity with Binary Pulsars. General relativity is a fully conservative theory, but there exist other possible metric theories of gravity. We consider nonconservative ones with a parameterized post-Newtonian parameter, ζ2. A nonzero ζ2 induces a self-acceleration for the center of mass of an eccentric binary pulsar system, which contributes to the second time derivative of the pulsar spin frequency, $\ddot{\nu }$ . In our work, using Will's method, we provide an improved analysis with four well-timed, carefully chosen binary pulsars. In addition, we extend Will's method and derive the effect of ${\zeta }_{2}$ on the third time derivative of the spin frequency, $\dddot{\nu }$ . For PSR B1913+16, the constraint from $\dddot{\nu }$ is even tighter than that from $\ddot{\nu }$ . We combine multiple pulsars with Bayesian inference, and obtain the upper limit, $\left|{\zeta }_{2}\right|\lt 1.3\times {10}^{-5}$ at the 95% confidence level, assuming a flat prior in ${\mathrm{log}}_{10}\left|{\zeta }_{2}\right|$ . It improves the existing bound by a factor of 3. Moreover, we propose an analytical timing formalism for ${\zeta }_{2}$ . Our simulated times of arrival with simplified assumptions show the capability of binary pulsars in limiting ζ2, and useful clues are extracted for real-data analysis in future. In particular, we discover that for PSRs B1913+16 and J0737-3039A, $\dddot{\nu }$ can yield more constraining limits than $\ddot{\nu }$ .

Keywords: Pulsar timing method, Millisecond pulsars, Gravitation, Relativistic binary stars, Non-standard theories of gravity, Gravitational interaction, Binary pulsars
Reconstructing the Coronal Magnetic Field: The Role of Cross-field Currents in Solution Uniqueness. We present a new 3D magnetohydrostatic (MHS) direct elliptic solver for extrapolating the coronal magnetic field from photospheric boundary conditions in a manner consistent with an assumed plasma distribution. We use it to study the uniqueness of the reconstructed magnetic field as a function of how significant the plasma forcing is on the force balance of the magnetic field. To this end, we consider an analytic MHS model as ground truth. The model uses two free parameters to decompose the current into two parts: a magnetic-field-aligned component and a cross-field component. We perform a comprehensive study of the 2D parameter space to understand under what conditions the ground truth can be reproduced uniquely. We find that current oriented perpendicular to the magnetic field has a smaller solution space than the same amount of current oriented parallel to the magnetic field, and so MHS regimes with larger proportions of plasma-related forcing may be a promising avenue toward finding unique magnetic field reconstructions.

Keywords: Solar magnetic fields, Computational methods, Solar corona, Magnetohydrodynamics
COSMIC Variance in Binary Population Synthesis. The formation and evolution of binary stars are critical components of several fields in astronomy. The most numerous sources for gravitational wave observatories are inspiraling or merging compact binaries, while binary stars are present in nearly every electromagnetic survey regardless of the target population. Simulations of large binary populations serve to both predict and inform observations of electromagnetic and gravitational wave sources. Binary population synthesis is a tool that balances physical modeling with simulation speed to produce large binary populations on timescales of days. We present a community-developed binary population synthesis suite, COSMIC, which is designed to simulate compact-object binary populations and their progenitors. As a proof of concept, we simulate the Galactic population of compact binaries and their gravitational wave signals observable by the Laser Interferometer Space Antenna.

Keywords: Stellar populations, Compact binary stars, Interacting binary stars, Gravitational wave astronomy
Helium Line Emissivities in the Solar Corona. We present new collisional-radiative models (CRMs) for helium in the quiescent solar corona and predict the emissivities of the He and He+ lines to be observed by DKIST, Solar Orbiter, and Proba-3. We discuss in detail the rates we selected for these models, highlighting several shortcomings we have found in previous work. As no previous complete and self-consistent coronal CRM for helium existed, we have benchmarked our largest model at a density of 106 cm-3 and temperature of 20,000 K against recent CRMs developed for photoionized nebulae. We then present results for the outer solar corona, using new dielectronic recombination rates we have calculated, which increase the abundance of neutral helium by about a factor of 2. We also find that all optical triplet He I lines, and in particular the well-known He I 10830 and 5876 Å lines, are strongly affected by both photoexcitation and photoionization from the disk radiation and that extensive CRMs are required to obtain correct estimates. Close to the Sun, at an electron density of 108 cm-3 and temperature of 1 MK, we predict the emissivity of He I 10830 Å to be comparable to that of the strong Fe XIII coronal line at 10798 Å. However, we expect the He I emissivity to sharply fall in the outer corona, with respect to Fe XIII. We confirm that the He+ Lyα at 304 Å is also significantly affected by photoexcitation and is expected to be detectable as a strong coronal line up to several solar radii.

Keywords: Photoionization, Atomic physics, Dielectronic recombination, Solar coronal lines, Collision physics, Quiet solar corona, Solar radiation, Radiative processes, Electron impact ionization, Transition probabilities
The Influence of Asymmetrical Distribution of Hemispheric Sunspot Areas on Some Solar Parameters' Periodicities during the Period 1945-2017: Wavelet Analysis. Monthly data of some solar parameters (the solar radio flux F10.7, the plage area PA, the coronal index CI, the solar mean magnetic field B, and the solar flare index SFI) during the period 1945-2017 have been classified into two groups (northern and southern) based on the distribution of the monthly averages of the hemispheric sunspot areas (SSAs). This has been done to investigate the symmetry and/or asymmetry in periodicities between the hemispheric groups for these parameters by utilizing the Morlet wavelet technique. For each of the considered parameters except B, it is observed that the most dominant and significant period (above the 95% confidence level) in both the wavelet spectra (WPS and GWS) for both hemispheric groups is the solar activity cycle at 10.7 yr during the entire time interval. The power values for other periods appeared to be quite small relative to that of the 10.7 yr period, and of less significance (below the 95% confidence level). For B, the most remarkable sign is the disappearance of the prominent peak of the solar activity cycle. The Hale cycle is clearly seen in both hemispheric groups of B, with a slight shift in time between the two hemispheric groups, and it increased through the entire considered duration. Periodicities of 10.7, 3.5, 1.5, and 0.8 yr have been observed in the northern hemispheric group of the parameters SSAs, F10.7, PA, CI, and SFI, indicating a possible correlation between them. For the southern hemispheric group, however, periodicities of 10.7, 5.4, and 0.8 yr have been revealed for the parameters F10.7, PA, and CI.

Keywords: Sunspot groups, Solar flares, Sunspot number, Plages, Active sun, Solar physics, Solar magnetic fields, Solar corona, Solar activity, Sunspot cycle
Revisiting the Impact of Dust Production from Carbon-rich Wolf-Rayet Binaries. We present a dust spectral energy distribution (SED) and binary stellar population analysis revisiting the dust production rates (DPRs) in the winds of carbon-rich Wolf-Rayet (WC) binaries and their impact on galactic dust budgets. DustEM SED models of 19 Galactic WC "dustars" reveal DPRs of ${\dot{M}}_{d}\sim {10}^{-10}\mbox{--}{10}^{-6}$ M☉ yr-1 and carbon dust condensation fractions, χC, between 0.002% and 40%. A large (0.1-1.0 μm) dust grain size composition is favored for efficient dustars where χC ≳ 1%. Results for dustars with known orbital periods verify a power-law relation between χC, orbital period, WC mass-loss rate, and wind velocity consistent with predictions from theoretical models of dust formation in colliding-wind binaries. We incorporated dust production into Binary Population and Spectral Synthesis (BPASS) models to analyze dust production rates from WC dustars, asymptotic giant branch stars (AGBs), red supergiants (RSGs), and core-collapse supernovae (SNe). BPASS models assuming constant star formation (SF) and a coeval 106 M☉ stellar population were performed at low, Large Magellanic Cloud (LMC)-like, and solar metallicities (Z = 0.001, 0.008, and 0.020). Both constant SF and coeval models indicate that SNe are net dust destroyers at all metallicities. Constant SF models at LMC-like metallicities show that AGB stars slightly outproduce WC binaries and RSGs by factors of 2-3, whereas at solar metallicities WC binaries are the dominant source of dust for ∼60 Myr until the onset of AGBs, which match the dust input of WC binaries. Coeval population models show that, for "bursty" SF, AGB stars dominate dust production at late times (t ≳ 70 Myr).

Keywords: Interstellar dust, WC stars, Infrared astronomy, Wolf-Rayet stars, Circumstellar dust
ALMA Observations of Multiple CO and C Lines toward the Active Galactic Nucleus of NGC 7469: An X-Ray-dominated Region Caught in the Act. We used the Atacama Large Millimeter/submillimeter Array to map 12CO(J = 1-0), 12CO(J = 2-1), 12CO(J = 3-2), 13CO(J = 2-1), and [C I](3P1-3P0) emission lines around the type 1 active galactic nucleus (AGN) of NGC 7469 (z = 0.0164) at ∼100 pc resolutions. The CO lines are bright in both the circumnuclear disk (central ∼300 pc) and the surrounding starburst (SB) ring (∼1 kpc diameter), with two bright peaks on either side of the AGN. By contrast, the [C I](3P1-3P0) line is strongly peaked on the AGN. Consequently, the brightness temperature ratio of [C I](3P1-3P0) to 13CO(2-1) is ∼20 at the AGN, as compared to ∼2 in the SB ring. Our local thermodynamic equilibrium (LTE) and non-LTE models indicate that the enhanced line ratios (or C I enhancement) are due to an elevated C0/CO abundance ratio (∼3-10) and temperature (∼100-500 K) around the AGN as compared to the SB ring (abundance ratio ∼1, temperature ≲100 K), which accords with the picture of the X-ray-dominated region. Based on dynamical modelings, we also provide CO(1-0)-to- and [C I](3P1-3P0)-to-molecular mass conversion factors at the central ∼100 pc of this AGN as αCO = 4.1 and αC I = 4.4 M⊙ (K km s-1 pc2)-1, respectively. Our results suggest that the C I enhancement is potentially a good marker of AGNs that could be used in a new submillimeter diagnostic method toward dusty environments.

Keywords: AGN host galaxies, Starburst galaxies, Astrochemistry, Seyfert galaxies, Active galactic nuclei, Interstellar medium
Rapid Rotation of Kepler Field Dwarfs and Subgiants: Spectroscopic v sin i from APOGEE. We use 5337 spectroscopic $v\sin i$ measurements of Kepler dwarfs and subgiants from the APOGEE survey to study stellar rotation trends. We find a detection threshold of 10 km s-1, which allows us to explore the spindown of intermediate-mass stars leaving the main sequence, merger products, young stars, and tidally synchronized binaries. We see a clear distinction between blue stragglers and the field turnoff in α-rich stars, with a sharp rapid rotation cutoff for blue stragglers consistent with the Kraft break. We also find rapid rotation and radial velocity variability in a sample of red straggler stars, considerably cooler than the giant branch, lending credence to the hypothesis that these are active, tidally synchronized binaries. We see clear evidence for a transition between rapid and slow rotation on the subgiant branch in the domain predicted by modern angular momentum evolution models. We find substantial agreement between the spectroscopic and photometric properties of KIC targets added by Huber et al. based on Two Micron All Sky Survey photometry. For the unevolved lower main sequence, we see the same concentration toward rapid rotation in photometric binaries as that observed in rotation period data, but at an enhanced rate. We attribute this difference to unresolved near-equal-luminosity spectroscopic binaries with velocity displacements on the order of the APOGEE resolution. Among cool unevolved stars we find an excess rapid rotator fraction of 4% caused by pipeline issues with photometric binaries.

Keywords: Stellar rotation, Subgiant stars, Late-type stars, Spectroscopy