Sazuna/UAT_keywords huggingface dataset:
The Impact of Cosmic Rays on Thermal Instability in the Circumgalactic Medium. Large reservoirs of cold (∼104 K) gas exist out to and beyond the virial radius in the circumgalactic medium (CGM) of all types of galaxies. Photoionization modeling suggests that cold CGM gas has significantly lower densities than expected by theoretical predictions based on thermal pressure equilibrium with hot CGM gas. In this work, we investigate the impact of cosmic-ray physics on the formation of cold gas via thermal instability. We use idealized three-dimensional magnetohydrodynamic simulations to follow the evolution of thermally unstable gas in a gravitationally stratified medium. We find that cosmic-ray pressure lowers the density and increases the size of cold gas clouds formed through thermal instability. We develop a simple model for how the cold cloud sizes and the relative densities of cold and hot gas depend on cosmic-ray pressure. Cosmic-ray pressure can help counteract gravity to keep cold gas in the CGM for longer, thereby increasing the predicted cold mass fraction and decreasing the predicted cold gas inflow rates. Efficient cosmic-ray transport, by streaming or diffusion, redistributes cosmic-ray pressure from the cold gas to the background medium, resulting in cold gas properties that are in between those predicted by simulations with inefficient transport and simulations without cosmic rays. We show that cosmic rays can significantly reduce galactic accretion rates and resolve the tension between theoretical models and observational constraints on the properties of cold CGM gas.

Keywords: Magnetohydrodynamical simulations, Galaxy evolution, Galaxy accretion, Circumgalactic medium, Astrophysical fluid dynamics, Cosmic rays
The Evolution of Disk Winds from a Combined Study of Optical and Infrared Forbidden Lines. We analyze high-resolution (∆v ≤ 10 km s-1) optical and infrared spectra covering the [O I] λ6300 and [Ne II] 12.81 μm lines from a sample of 31 disks in different evolutionary stages. Following work at optical wavelengths, we use Gaussian profiles to fit the [Ne II] lines and classify them into high-velocity component (HVC) or low-velocity component (LVC) if the line centroid is more or less blueshifted than 30 km s-1 with respect to the stellar radial velocity, respectively. Unlike for the [O I], where an HVC is often accompanied by an LVC, all 17 sources with an [Ne II] detection have either an HVC or an LVC. [Ne II] HVCs are preferentially detected toward high accretors ( ${\dot{M}}_{\mathrm{acc}}\gt {10}^{-8}$ M☉ yr-1), while LVCs are found in sources with low ${\dot{M}}_{\mathrm{acc}}$ , low [O I] luminosity, and large infrared spectral index (n13-31). Interestingly, the [Ne II] and [O I] LVC luminosities display an opposite behavior with n13-31: as the inner dust disk depletes (higher n13-31), the [Ne II] luminosity increases while the [O I] weakens. The [Ne II] and [O I] HVC profiles are generally similar, with centroids and FWHMs showing the expected behavior from shocked gas in microjets. In contrast, the [Ne II] LVC profiles are typically more blueshifted and narrower than the [O I] profiles. The FWHM and centroid versus disk inclination suggest that the [Ne II] LVC predominantly traces unbound gas from a slow, wide-angle wind that has not lost completely the Keplerian signature from its launching region. We sketch an evolutionary scenario that could explain the combined [O I] and [Ne II] results and includes screening of hard (∼1 keV) X-rays in inner, mostly molecular, MHD winds.

Keywords: Stellar accretion disks, Stellar jets, Protoplanetary disks
On the X-Ray Spectral Energy Distributions of Star-forming Galaxies: The 0.3-30 keV Spectrum of the Low-metallicity Starburst Galaxy VV 114. Binary population synthesis combined with cosmological models suggests that X-ray emission from star-forming galaxies, consisting primarily of emission from X-ray binaries (XRBs) and the hot interstellar medium (ISM), could be an important, and perhaps dominant, source of heating of the intergalactic medium prior to the epoch of reionization. However, such models rely on empirical constraints for the X-ray spectral energy distributions (SEDs) of star-forming galaxies, which are currently lacking for low-metallicity galaxies. Using a combination of Chandra, XMM-Newton, and NuSTAR observations, we present new constraints on the 0.3-30 keV SED of the low-metallicity starburst galaxy VV 114, which is known to host several ultraluminous X-ray sources (ULXs) with luminosities above 1040 erg s-1. We use an archival Chandra observation of VV 114 to constrain the contributions to the X-ray SED from the major X-ray-emitting components of the galaxy and newly acquired, nearly simultaneous XMM-Newton and NuSTAR observations to extend the spectral model derived from Chandra to cover the 0.3-30 keV range. Using our best-fit galaxy-wide spectral model, we derive the 0.3-30 keV SED of VV 114, which we find is dominated by emission from the XRB population, and in particular ULXs, at energies &gt;1.5 keV, and which we find to have an elevated galaxy-integrated X-ray luminosity per unit star formation rate relative to higher-metallicity star-forming galaxies. We discuss our results in terms of the effect of metallicity on XRB populations and the hot ISM, as well as the importance of X-ray emission from star-forming galaxies in the high-redshift universe.

Keywords: Starburst galaxies, X-ray binary stars, Interstellar medium
Four-dimensional Frequency-Wavenumber Power Spectrum of a Strong Turbulence Obtained from Hybrid Kinetic Simulations. We carry out three-dimensional hybrid kinetic simulations of a strong decaying turbulence. The turbulence is initiated with a seed spectrum that includes Alfvén wave modes at low wavenumbers. From the temporal and spatial distribution of the simulation output in the quasi-steady phase, we calculate a four-dimensional frequency-wavenumber spectrum of the turbulence. Our analysis shows that kinetic Alfvén waves can be identified in the wavenumber-frequency space in the vicinity of the seed turbulence spectrum. They produce a power peak consistent with a linear dispersion relation. However, further away from the seed spectrum, where most of the wave-particle interaction takes place, the signature of the Alfvén modes disappears among other fluctuations that are not described by any dispersion relations. Furthermore, at higher wavenumbers at which the signature is still identifiable, its frequency broadening becomes comparable to the frequency itself. Therefore, the use of linear waves based on the conventional dispersion relation is not necessarily justified to describe the turbulence if their signature is still present and even more so when it disappears. We find that at larger rms amplitudes of the turbulence, the signature of the dispersion relation is confined to lower parallel wavenumbers. In the range where it is visible, the frequency broadening becomes greater at larger amplitudes. This suggests that stronger nonlinearity makes the fluctuations behave less like wave modes until the conventional wave-mode approach is no longer valid.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind
The Discovery of Nulling and Mode-switching Pulsars with CHIME/Pulsar. The Pulsar backend of the Canadian Hydrogen Intensity Mapping Experiment has monitored hundreds of known pulsars in the northern sky since fall 2018, providing a rich data set for the study of temporal variations in pulsar emission. Using a matched filtering technique, we report, for the first time, nulling behavior in five pulsars as well as mode switching in nine pulsars. Only one of the pulsars is observed to show both nulling and moding signals. These new nulling and mode-switching pulsars appear to come from a population with relatively long spin periods, in agreement with previous findings in the literature.

Keywords: Observational astronomy, Neutron stars, Pulsars, Radio astronomy, Astronomical methods
Simulations of the Early Postbounce Phase of Core-collapse Supernovae in Three-dimensional Space with Full Boltzmann Neutrino Transport. We report on the core-collapse supernova simulation we conducted for a 11.2M⊙ progenitor model in three-dimensional space up to 20 ms after bounce, using a radiation-hydrodynamics code with full Boltzmann neutrino transport. We solve the six-dimensional Boltzmann equations for three neutrino species and the three-dimensional compressible Euler equations with Furusawa and Togashi's nuclear equation of state. We focus on the prompt convection at ∼10 ms after bounce and investigate how neutrinos are transported in the convective matter. We apply a new analysis based on the eigenvalues and eigenvectors of the Eddington tensor and make a comparison between the Boltzmann transport results and the M1 closure approximation in the transition regime between the optically thick and thin limits. We visualize the eigenvalues and eigenvectors using an ellipsoid, in which each principal axis is parallel to one of the eigenvectors and has a length proportional to the corresponding eigenvalue. This approach enables us to understand the difference between the Eddington tensor derived directly from the Boltzmann simulation and the one given by the M1 prescription from a new perspective. We find that the longest principal axis of the ellipsoid is almost always nearly parallel to the energy flux in the M1 closure approximation, whereas in the Boltzmann simulation it becomes perpendicular in some transition regions, where the mean free path is ∼0.1 times the radius. In three spatial dimensions, the convective motions make it difficult to predict where this happens and to possibly improve the closure relation there.

Keywords: Core-collapse supernovae
Cosmological Parameter Estimation for Dynamical Dark Energy Models with Future Fast Radio Burst Observations. Fast radio bursts (FRBs) are a mysterious astrophysical phenomenon of bright pulses emitted at radio frequencies, and they are expected to be frequently detected in the future. The dispersion measures of FRBs are related to cosmological parameters, thus FRBs have the potential to be developed into a new cosmological probe if their data can be largely accumulated in the future. In this work, we study the capability of future FRB data to improve cosmological parameter estimation in two dynamical dark energy models. We find that the simulated FRB data can break the parameter degeneracies inherent in the current cosmic microwave background (CMB) data. Therefore, the combination of CMB and FRB data can significantly improve the constraints on the Hubble constant and dark energy parameters, compared to those using CMB or FRB alone. If 10,000 FRB events with known redshifts are detected in the future, they would perform better than the baryon acoustic oscillation (BAO) data in breaking the parameter degeneracies inherent in the CMB data. We also find that the combination of FRB and gravitational-wave (GW) standard siren data provides an independent low-redshift probe to verify the results from the CMB and BAO data. For the data combination of CMB, GW, and FRB, it is found that the main contribution to the constraints comes from the CMB and GW data, but the inclusion of the FRB data still can evidently improve the constraint on the baryon density.

Keywords: Cosmology, Cosmological parameters, Extragalactic radio sources, Gravitational waves, Dark energy
Electron Acceleration Rate at Dipolarization Fronts. Although it has been shown that betatron and Fermi mechanisms contribute to electron acceleration at the dipolarization front (DF), the relative efficiency of these acceleration processes is unclear. In this paper, we directly calculate the electron adiabatic acceleration rate (the instantaneous acceleration) at DFs by using the data from the Magnetospheric Multiscale mission. We find that betatron acceleration dominates at the DF. Although the Fermi acceleration rate is smaller than the betatron acceleration rate, it is effective on a larger spatial scale than betatron acceleration, which is localized at the DF proper. The acceleration by the parallel electric field is negligible because it is far below the measurement uncertainties. The dependence of these acceleration rates on the DF normal, magnetic field, and thickness of the DF are analyzed. Our results provide important information for understanding the electron acceleration in the Earth's magnetotail.

Keywords: Space plasmas, Planetary interior
Accretion History of AGNs. III. Radiative Efficiency and AGN Contribution to Reionization. The cosmic history of supermassive black hole (SMBH) growth is important for understanding galaxy evolution, reionization, and the physics of accretion. Recent NuSTAR, Swift-BAT, and Chandra hard X-ray surveys have provided new constraints on the space density of heavily obscured active galactic nuclei (AGNs). Using the new X-ray luminosity function derived from these data, we here estimate the accretion efficiency of SMBHs and their contribution to reionization. We calculate the total ionizing radiation from AGNs as a function of redshift, based on the X radiation and distribution of obscuring column density, converted to ultraviolet (UV) wavelengths. Limiting the luminosity function to unobscured AGNs only, our results agree with current UV luminosity functions of unobscured AGNs. For realistic assumptions about the escape fraction, the contribution of all AGNs to cosmic reionization is ∼4 times lower than the galaxy contribution (23% at z ∼ 6). Our results also offer an observationally constrained prescription that can be used in simulations or models of galaxy evolution. To estimate the average efficiency with which SMBHs convert mass to light, we compare the total radiated energy, converted from X-ray light using a bolometric correction, with the most recent local black hole mass density. The most likely value, η ∼ 0.3-0.34, approaches the theoretical limit for a maximally rotating Kerr black hole, η = 0.42, implying that on average growing SMBHs are spinning rapidly.

Keywords: Accretion, High energy astrophysics, X-ray active galactic nuclei, Active galactic nuclei, Reionization
Scatter Analysis along the Multidimensional Radius-Luminosity Relations for Reverberation-mapped Mg II Sources. The usage of the radius-luminosity (R-L) relation for the determination of black hole masses across the cosmic history, as well as its application for cosmological studies, motivates us to analyze its scatter, which has recently increased significantly for both the optical (Hβ) and UV (Mg II) lines. To this purpose, we determined the scatter along the R-L relation for an up-to-date reverberation-mapped Mg II sample. Studying linear combinations of the luminosity at 3000 Å with independent parameters such as the FWHM, the UV Fe II strength (RFe II), and the fractional variability (Fvar) for the whole sample, we get only a small decrease in the scatter ( ${\sigma }_{\mathrm{rms}}=0.29\,-0.30$ dex). Linear combinations with the dimensionless accretion rate ( $\dot{\,{ \mathcal M }}$ ) and the Eddington ratio lead to significant reductions of the scatter ( ${\sigma }_{\mathrm{rms}}\sim 0.1$ dex), albeit both suffering from the interdependency on the observed time delay. After the division into two subsamples considering the median value of the $\dot{\,{ \mathcal M }}$ in the full sample, we find that the scatter decreases significantly for the highly accreting subsample. In particular, the smallest scatter of ${\sigma }_{\mathrm{rms}}=0.17$ dex is associated with the independent parameter RFe II, followed by the combination with Fvar with ${\sigma }_{\mathrm{rms}}=0.19$ dex. Both of these independent observationally inferred parameters are in turn correlated with $\dot{{ \mathcal M }}$ and ${L}_{\mathrm{bol}}/{L}_{\mathrm{Edd}}$ . These results suggest that the large scatter along the R-L relation is driven mainly by the accretion rate intensity.

Keywords: Supermassive black holes, Active galaxies
Universal at Last? The Splashback Mass Function of Dark Matter Halos. The mass function of dark matter halos is one of the most fundamental statistics in structure formation. Many theoretical models (such as Press-Schechter theory) are based on the notion that it could be universal, meaning independent of redshift and cosmology, when expressed in the appropriate variables. However, simulations exhibit persistent nonuniversalities in the mass functions of the virial mass and other commonly used spherical overdensity definitions. We systematically study the universality of mass functions over a wide range of mass definitions, for the first time including the recently proposed splashback mass, ${M}_{\mathrm{sp}}$ . We confirm that, in ΛCDM cosmologies, all mass definitions exhibit varying levels of nonuniversality that increase with peak height and reach between 20% and 500% at the highest masses we can test. ${M}_{\mathrm{vir}}$ , ${M}_{200{\rm{m}}}$ , and ${M}_{\mathrm{sp}}$ exhibit similar levels of nonuniversality. There are, however, two regimes where the splashback mass functions are significantly more universal. First, they are universal to 10% at $z\leqslant 2$ , whereas spherical overdensity definitions experience an evolution due to dark energy. Second, when additionally considering self-similar cosmologies with extreme power spectra, splashback mass functions are remarkably universal (to between 40% and 60%), whereas their spherical overdensity counterparts reach nonuniversalities between 180% and 450%. These results strongly support the notion that the splashback radius is a physically motivated definition of the halo boundary. We present a simple and universal fitting formula for splashback mass functions that accurately reproduces our simulation data.

Keywords: Large-scale structure of the universe
Cosmological Insights into the Early Accretion of r-process-enhanced Stars. I. A Comprehensive Chemodynamical Analysis of LAMOST J1109+0754. This study presents a comprehensive chemodynamical analysis of LAMOST J1109+0754, a bright (V = 12.8), extremely metal-poor ([Fe/H] = -3.17) star, with a strong r-process enhancement ([Eu/Fe] = +0.94 ± 0.12). Our results are based on the 7D measurements supplied by Gaia and the chemical composition derived from a high-resolution (R ∼ 110,000), high signal-to-noise ratio ( ${\rm{S}}/{\rm{N}}\sim 60)$ optical spectrum obtained by the 2.4 m Automated Planet Finder Telescope at Lick Observatory. We obtain chemical abundances of 31 elements (from lithium to thorium). The abundance ratios ([X/Fe]) of the light elements (Z ≤ 30) suggest a massive Population III progenitor in the 13.4-29.5 M⊙ mass range. The heavy-element (30 &lt; Z ≤ 90) abundance pattern of J1109+075 agrees extremely well with the scaled-solar r-process signature. We have developed a novel approach to trace the kinematic history and orbital evolution of J1109+0754 with a cOsmologically deRIved timE-varyiNg Galactic poTential (the ORIENT) constructed from snapshots of a simulated Milky Way analog taken from the Illustris-TNG simulation. The orbital evolution within this Milky Way-like galaxy, along with the chemical abundance pattern, implies that J1109+0754 likely originated in a low-mass dwarf galaxy located ∼60 kpc from the center of the Galaxy, which was accreted ∼6-7 Gyr ago, and that the star now belongs to the outer-halo population.

Keywords: Population III stars, Stellar kinematics, R-process, Orbits, Galaxy dynamics, Chemical abundances, Stellar dynamics, Chemically peculiar stars
Prediction and Understanding of Soft-proton Contamination in XMM-Newton: A Machine Learning Approach. One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes are few tens to hundreds of keV (soft) protons concentrated by the mirrors. One such telescope is the European Space Agency's (ESA) X-ray Multi-Mirror Mission (XMM-Newton). Its observing time lost due to background contamination is about 40%. This loss of observing time affects all the major broad science goals of this observatory, ranging from cosmology to astrophysics of neutron stars and black holes. The soft-proton background could dramatically impact future large X-ray missions such as the ESA planned Athena mission (http://www.the-athena-x-ray-observatory.eu/). Physical processes that trigger this background are still poorly understood. We use a machine learning (ML) approach to delineate related important parameters and to develop a model to predict the background contamination using 12 yr of XMM-Newton observations. As predictors we use the location of the satellite and solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in the southern direction, Z (XMM-Newton observations were in the southern hemisphere), the solar wind radial velocity, and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the first two individual predictors and an ML model that utilizes an ensemble of the predictors (Extra-Trees Regressor) and gives better performance. Based on our analysis, future missions should minimize observations during times associated with high solar wind speed and avoid closed magnetic field lines, especially at the dusk flank region in the southern hemisphere.

Keywords: Space plasmas, Astronomy data modeling, X-ray detectors, Astronomy data analysis, X-ray telescopes, X-ray observatories
A Model of Rotating Convection in Stellar and Planetary Interiors. II. Gravito-inertial Wave Generation. Gravito-inertial waves are excited at the interface of convective and radiative regions and by the Reynolds stresses in the bulk of the convection zones of rotating stars and planets. Such waves have notable asteroseismic signatures in the frequency spectra of rotating stars, particularly among rapidly rotating early-type stars, which provides a means of probing their internal structure and dynamics. They can also transport angular momentum, chemical species, and energy from the excitation region to where they dissipate in radiative regions. To estimate the excitation and convective parameter dependence of the amplitude of those waves, a monomodal model for stellar and planetary convection as described in Paper I is employed, which provides the magnitude of the rms convective velocity as a function of rotation rate. With this convection model, two channels for wave driving are considered: excitation at a boundary between convectively stable and unstable regions and excitation due to Reynolds stresses. Parameter regimes are found where the sub-inertial waves may carry a significant energy flux, depending upon the convective Rossby number, the interface stiffness, and the wave frequency. The super-inertial waves can also be enhanced, but only for convective Rossby numbers near unity. Interfacially excited waves have a peak energy flux near the lower cutoff frequency when the convective Rossby number of the flows that excite them are below a critical Rossby number that depends upon the stiffness of the interface, whereas that flux decreases when the convective Rossby number is larger than this critical Rossby number.

Keywords: Stellar convective zones, Stellar dynamics, Stellar physics, Stellar oscillations, Stellar rotation