Sazuna/UAT_keywords huggingface dataset:
Thermal State of the Intergalactic Medium at z ∼ 2-4. We present a new method to infer parameters of the temperature-density relation in the intergalactic medium in the post-reionization epoch at z ∼ 2-4. This method is based on the analysis of the distribution of Lyα absorbers over column densities and Doppler parameters by the model joint probability density function. This approach allows us to measure the power-law index γ of the temperature-density relation and a certain combination of the temperature at the mean density T 0 and hydrogen photoionization rate Γ. To estimate T 0 and Γ separately, we employ measurements of the Lyα forest effective opacity and the model gas probability density function. We show that γ tends to be lower than 1.6 and reaches 1.3 at redshift ∼3. The inferred temperatures at the mean density are ∼(2 ± 0.5) × 104 K in the studied redshift range. Both these estimates favor He II reionization at z ≳ 3. We find that the hydrogen photoionization rate is ∼0.6 × 10-12 s-1, which is consistent with previous measurements.

Keywords: Early universe, Reionization, Intergalactic medium
Deep ATCA and VLA Radio Observations of Short-GRB Host Galaxies. Constraints on Star Formation Rates, Afterglow Flux, and Kilonova Radio Flares. We report the results of an extensive radio-continuum observing campaign of host galaxies of short gamma-ray bursts (GRBs). The goal of this survey was to search for optically obscured star formation, possibly indicative of a population of young short-GRB progenitors. Our sample comprises the hosts and host-galaxy candidates of 16 short-GRBs from 2005 to 2015, corresponding to roughly one-third of the presently known ensemble of well-localized short bursts. Eight GRB fields were observed with ATCA (at 5.5 and 9.0 GHz), and eight fields with the VLA (mostly at 5.5 GHz). The observations typically achieved a 1σ rms of 5-8 μJy. In most cases, they were performed years after the corresponding burst. No new short-GRB host with optically obscured star formation was found. Only one host galaxy was detected: that of GRB 100206A at z = 0.407. However, its starburst nature was already known from optical/IR data. Its measured radio flux can be interpreted as being due to a star formation rate of about 60 M ☉ yr-1. This is in good agreement with earlier expectations based on the observed broad-band spectral energy distribution of this galaxy. The 15 nondetections constrain the SFRs of the suspected host galaxies and provide upper limits on late-time luminosities of the associated radio afterglows and predicted kilonova radio flares. The nondetection of radio emission from GRB explosion sites confirms the intrinsically low luminosity of short-GRB afterglows and places significant constraints on the parameter space of magnetar-powered radio flares. Luminous radio flares from fiducial massive magnetars have not been found.

Keywords: Gamma-ray bursts, Transient sources, High energy astrophysics
The Contribution of Galaxies to the 3.4 μm Cosmic Infrared Background as Measured Using WISE. The study of the extragalactic background light (EBL) in the optical and near-infrared has received a lot of attention in the last decade, especially near the wavelength λ ≈ 3.4 μm, with remaining tension among different techniques for estimating the background. In this paper we present a measurement of the contribution of galaxies to the EBL at 3.4 μm that is based on the measurement of the luminosity function (LF) in Lake et al. and the mean spectral energy distribution of galaxies in Lake &amp; Wright. The mean and standard deviation of our most reliable Bayesian posterior chain gives a 3.4 μm background of I  ν  = 9.0 ± 0.5 kJy sr-1 (νI  ν  = 8.0 ± 0.4 nW m-2 sr-1 e-fold-1), with systematic uncertainties unlikely to be greater than 2 kJy sr-1. This result is higher than most previous efforts to measure the contribution of galaxies to the 3.4 μm EBL, but is consistent with the upper limits placed by blazars and the most recent direct measurements of the total 3.4 μm EBL.

Keywords: Infrared galaxies, Galaxy evolution, Infrared sources, Extragalactic astronomy, Cosmic background radiation
Proton-Proton Collisions in the Turbulent Solar Wind: Hybrid Boltzmann-Maxwell Simulations. The mechanism of heating for hot, dilute, and turbulent plasmas represents a long-standing problem in space physics, whose implications concern both near-Earth environments and astrophysical systems. In order to explore the possible role of interparticle collisions, simulations of plasma turbulence—in both collisionless and weakly collisional regimes—have been compared by adopting Eulerian Hybrid Boltzmann-Maxwell simulations, being proton-proton collisions explicitly introduced through the nonlinear Dougherty operator. Although collisions do not significantly influence the statistical characteristics of the turbulence, they dissipate nonthermal features in the proton distribution function and suppress the enstrophy/entropy cascade in the velocity space, damping the spectral transfer toward large Hermite modes. This enstrophy dissipation is particularly effective in regions where the plasma distribution function is strongly distorted, suggesting that collisional effects are enhanced by fine velocity-space structures. A qualitative connection between the turbulent energy cascade in fluids and the enstrophy cascade in plasmas has been established, opening a new path to the understanding of astrophysical plasma turbulence.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind, Plasma physics
Protostellar Evolution in Serpens Main: Possible Origin of Disk-size Diversity. We have observed the submillimeter continuum condensations SMM2, SMM4, SMM9, and SMM11 in the star-forming cluster Serpens Main using the Atacama Large Millimeter/submillimeter Array during Cycle 3 in the 1.3 mm continuum, 12CO J = 2 - 1, SO J  N  = 65 - 54, and C18O J = 2 - 1 lines at an angular resolution of ∼0.″55 (240 au). Sixteen sources have been detected in the 1.3 mm continuum, which can be classified into three groups. Group 1 consists of six sources showing extended continuum emission and bipolar/monopolar 12CO outflows. Although all the Group 1 members are classified as Class 0 protostars, our observations suggest evolutionary trends among them in terms of 12CO outflow dynamical time, SO emission distribution, C18O fractional abundance, and continuum morphology. Group 2 consists of four sources associated with a continuum filamentary structure and no 12CO outflows. Central densities estimated from the 1.3 mm continuum intensity suggest that they are prestellar sources in a marginally Jeans unstable state. Group 3 consists of six Spitzer sources showing point-like 1.3 mm continuum emission and clumpy 12CO outflows. These features of Group 3 suggest envelope dissipation, preventing disk growth from the present size, r ≲ 60 au. The Group 3 members are protostars that may be precursors to the T Tauri stars associated with small disks at radii, of tens of astronomical units, identified in recent surveys.

Keywords: Circumstellar matter, Protostars, Low mass stars
Impact of a Spinning Supermassive Black Hole on the Orbit and Gravitational Waves of a Nearby Compact Binary. Recent theoretical studies suggest that stellar-mass binary black holes (BBHs) would merge more efficiently due to the Kozai-Lidov (K-L) mechanism if these binaries form in the vicinity of supermassive black holes (SMBHs). Since SMBHs are likely rotating rapidly, we continue our earlier study on the generalization of the K-L formalism to include the spin of the SMBH and study the evolution of a nearby BBH. We find that the eccentricity and orbital inclination of the BBH are significantly affected, because the spin (i) forces the orbital plane of the center-of-mass of the BBH around the SMBH to precess (the Lense-Thirring effect) and (ii) imposes an additional gravitomagnetic force on the BBH. As a result, the merger time of the BBH could be significantly different. We calculate the waveform from the BBH in one representative example and study its detectability with a milli-Hertz gravitational-wave detector, such as the Laser Interferometer Space Antenna (LISA). We find that the signal is distinguishable from that in the case without spin. Our results imply that the BBHs in the LISA band could potentially be used to probe the spin of the SMBHs in galaxy centers.

Keywords: General relativity, Gravitational waves, Gravitational wave sources, Stellar dynamics
Primordial Earth Mantle Heterogeneity Caused by the Moon-forming Giant Impact?. The giant impact hypothesis for Moon formation successfully explains the dynamic properties of the Earth-Moon system but remains challenged by the similarity of isotopic fingerprints of the terrestrial and lunar mantles. Moreover, recent geochemical evidence suggests that the Earth’s mantle preserves ancient (or “primordial”) heterogeneity that pre-dates the Moon-forming giant impact. Using a new hydrodynamical method, we here show that Moon-forming giant impacts lead to a stratified starting condition for the evolution of the terrestrial mantle. The upper layer of the Earth is compositionally similar to the disk, out of which the Moon evolves, whereas the lower layer preserves proto-Earth characteristics. As long as this predicted compositional stratification can at least partially be preserved over the subsequent billions of years of Earth mantle convection, a compositional similarity between the Moon and the accessible Earth’s mantle is a natural outcome of realistic and high-probability Moon-forming impact scenarios. The preservation of primordial heterogeneity in the modern Earth not only reconciles geochemical constraints but is also consistent with recent geophysical observations. Furthermore, for significant preservation of a proto-Earth reservoir, the bulk major-element composition of the Earth-Moon system may be systematically shifted toward chondritic values.

Keywords: Lunar composition, Natural satellite formation, Earth (planet), Computational methods, Earth-moon system
MAESTROeX: A Massively Parallel Low Mach Number Astrophysical Solver. We present MAESTROeX, a massively parallel solver for low Mach number astrophysical flows. The underlying low Mach number equation set allows for efficient, long-time integration for highly subsonic flows compared to compressible approaches. MAESTROeX is suitable for modeling full spherical stars as well as well as planar simulations of dynamics within localized regions of a star, and can robustly handle several orders of magnitude of density and pressure stratification. Previously, we have described the development of the predecessor of MAESTROeX, called MAESTRO, in a series of papers. Here, we present a new, greatly simplified temporal integration scheme that retains the same order of accuracy as our previous approaches. We also explore the use of alternative spatial mapping of the one-dimensional base state onto the full Cartesian grid. The code leverages the new AMReX software framework for block-structured adaptive mesh refinement (AMR) applications, allowing for scalability to large fractions of leadership-class machines. Using our previous studies on the convective phase of single-degenerate progenitor models of SNe Ia as a guide, we characterize the performance of the code and validate the new algorithmic features. Like MAESTRO, MAESTROeX is fully open source.

Keywords: Stellar convective zones, Nucleosynthesis, Hydrodynamics, Nuclear abundances, Computational methods, Nuclear astrophysics
Stochastic Chemical Evolution of Radioactive Isotopes with a Monte Carlo Approach. Short-lived radionuclides (SLRs) with mean lives τ of a few to hundreds of Myr provide unique opportunities to probe recent nucleosynthesis events in the interstellar medium and the physical conditions in which the Sun formed. Here we quantify the uncertainty in the predicted evolution of SLRs within a parcel of interstellar gas given the stochastic nature of stellar enrichment events. We assume that an enrichment progenitor is formed at every time interval γ. For each progenitor, we randomly sample the delay time between its formation and its enrichment event, based on several delay-time distribution (DTD) functions that cover a wide range of astrophysical sites. For each set of τ, γ, and DTD functions, we follow the abundances of SLRs for 15 Gyr and repeat this process thousands of times to derive their probability distributions. For τ/γ ≳ 2, the distributions depend on the DTD function, and we provide tabulated values and analytical expressions to quantify the spread. The relative abundance uncertainty reaches a maximum of ∼60% for τ/γ = 1. For τ/γ ≲ 1, we provide the probability for the SLR abundance to carry the signature of only one enrichment event, which is greater than 50% when τ/γ ≲ 0.3. For 0.3 ≲ τ/γ ≲ 2, a small number of events contributed to the SLR abundance. This case needs to be investigated with a separate statistical method. We find that an isolation time for the birth of the Sun of roughly 9-13 Myr is consistent with the observed abundances of 60Fe, 107Pd, and 182Hf in the early solar system when assuming τ/γ ∼ 3 for these isotopes.

Keywords: Meteorites, Solar system formation, Interstellar abundances
Planck Far-infrared Detection of Hyper Suprime-Cam Protoclusters at z ∼ 4: Hidden AGN and Star Formation Activity. We perform a stacking analysis of Planck, AKARI, Infrared Astronomical Satellite, Wide-field Infrared Survey Explorer, and Herschel images of the largest number of (candidate) protoclusters at z ∼ 3.8 selected from the Hyper Suprime-Cam Subaru Strategic Program. Stacking the images of the 179 candidate protoclusters, the combined infrared (IR) emission of the protocluster galaxies in the observed 12-850 μm wavelength range is successfully detected with &gt;5σ significance (at Planck). This is the first time that the average IR spectral energy distribution (SED) of a protocluster has been constrained at z ∼ 4. The observed IR SEDs of the protoclusters exhibit significant excess emission in the mid-IR compared to that expected from typical star-forming galaxies (SFGs). They are reproduced well using SED models of intense starburst galaxies with warm/hot dust heated by young stars, or by a population of active galactic nucleus (AGN)/SFG composites. For the pure star-forming model, a total IR (from 8-1000 μm) luminosity of {19.3}-4.2+0.6× {10}13 {L}⊙  and a star formation rate of {16.3}-7.8+1.0× {10}3 {M}⊙  yr-1 are found, whereas for the AGN/SFG composite model, {5.1}-2.5+2.5× {10}13 {L}⊙  and {2.1}-1.7+6.3× {10}3 {M}⊙  yr-1 are found. Uncertainty remains in the total SFRs; however, the IR luminosities of the most massive protoclusters are likely to continue increasing up to z ∼ 4. Meanwhile, no significant IR flux excess is observed around optically selected QSOs at similar redshifts, which confirms previous results. Our results suggest that the z ∼ 4 protoclusters trace dense, intensely star-forming environments that may also host obscured AGNs missed by the selection in the optical.

Keywords: Protoclusters, Galaxy evolution
On the Origin of Solar Torsional Oscillations and Extended Solar Cycle. We present a nonlinear mean-field model of the solar interior dynamics and dynamo, which reproduces the observed cyclic variations of the global magnetic field of the Sun, as well as the differential rotation and meridional circulation. Using this model, we explain, for the first time, the extended 22 yr pattern of the solar torsional oscillations, observed as propagation of zonal variations of the angular velocity from high latitudes to the equator during the time equal to the full dynamo cycle. In the literature, this effect is usually attributed to the so-called “extended solar cycle.” In agreement with the commonly accepted idea, our model shows that the torsional oscillations can be driven by a combination of magnetic field effects acting on turbulent angular momentum transport and the large-scale Lorentz force. We find that the 22 yr pattern of the torsional oscillations can result from a combined effect of an overlap of subsequent magnetic cycles and magnetic quenching of the convective heat transport. The latter effect results in cyclic variations of the meridional circulation in the sunspot formation zone, in agreement with helioseismology results. The variations of the meridional circulation, together with other drivers of the torsional oscillations, maintain their migration to the equator during the 22 yr magnetic cycle, resulting in the observed extended pattern of the torsional oscillations.

Keywords: Solar cycle, Solar differential rotation, Solar dynamo, Solar meridional circulation
Imaging the Sun's Far-side Active Regions by Applying Multiple Measurement Schemes on Multiskip Acoustic Waves. Being able to image active regions (ARs) on the Sun’s far side is useful for modeling the global-scale magnetic field around the Sun and for predicting the arrival of major ARs that rotate around the limb onto the near side. Helioseismic methods have already been developed to image the Sun’s far-side ARs using near-side high-cadence Doppler-velocity observations; however, the existing methods primarily explore the 3-, 4-, and 5-skip helioseismic waves, leaving room for further improvement in the imaging quality by including waves with more multiskip waves. Taking advantage of the fact that 6-skip waves have the same target-annuli geometry as 3- and 4-skip waves and that 8-skip waves have the same target-annuli geometry as 4-skip waves, we further develop a time-distance helioseismic code to include a total of 14 sets of measurement schemes. We then apply the new code on the Solar Dynamics Observatory/Helioseismic and Magnetic Imager observed Dopplergrams and find that the new code provides substantial improvements over the existing codes in mapping newly emerged ARs and ARs near both far-side limbs. Comparing 3 months of far-side helioseismic images with the Solar TErrestrial RElations Observatory/Extreme UltraViolet Imager observed 304 Å images, we find that 97.3% of the helioseismically detected far-side ARs that are larger than a certain size correspond to an observed region with strong EUV brightening. The high reliability of the new imaging tool will potentially allow us to further calibrate the far-side helioseismic images into maps of magnetic flux.

Keywords: Solar ultraviolet emission, Helioseismology, Sunspots, Solar active regions, Solar magnetic fields, Solar oscillations
Radiation Pressure from Interstellar Hydrogen Observed by IBEX through Solar Cycle 24. As the Sun moves through the local interstellar medium (LISM), neutral atoms travel through the heliosphere and can be detected by IBEX. We consider interstellar neutral (ISN) hydrogen atoms with a drifting Maxwellian distribution function in the LISM that travel on almost hyperbolic trajectories to the inner heliosphere. They are subject to solar gravity and radiation pressure, as well as ionization processes. For ISN H, the radiation pressure, which exerts an effective force comparable to gravitation, decelerates individual atoms and shifts the longitude of their observed peak relative to that of ISN He. We used the peak longitude of the observed flux in the lowest energy channel of IBEX-Lo to investigate how radiation pressure shifts the ISN H signal over almost an entire solar cycle (2009-2018). Thus, we have created a new methodology to determine the Lyα effective radiation pressure from IBEX ISN H data. The resulting effective ratio of the solar radiation pressure and gravitation (μ eff = 1.074 ± 0.038), averaged over cycle 24, appears to agree within the uncertainties with simulations based on total irradiance observations7 while being higher by ∼21%. Our analysis indicates an increase of μ eff with solar activity, albeit with substantial uncertainties. Further study of IBEX H response functions and future Interstellar Mapping and Acceleration Probe data should provide significant reduction of the uncertainties and improvements in our understanding of the effects of radiation pressure on ISN atoms.

Keywords: Space plasmas, Heliosphere, Interstellar atomic gas, Solar wind, Interstellar medium, Solar activity
The Spectral Evolution of AT 2018dyb and the Presence of Metal Lines in Tidal Disruption Events. We present light curves and spectra of the tidal disruption event (TDE) ASASSN-18pg/AT 2018dyb spanning a period of one year. The event shows a plethora of strong emission lines, including the Balmer series, He II, He I, and metal lines of O III λ3760 and N III λλ4100, 4640 (blended with He II). The latter lines are consistent with originating from the Bowen fluorescence mechanism. By analyzing literature spectra of past events, we conclude that these lines are common in TDEs. The spectral diversity of optical TDEs is thus larger than previously thought and includes N-rich events besides H- and He-rich events. We study how the spectral lines evolve with time, by means of their width, relative strength, and velocity offsets. The velocity width of the lines starts at ∼13,000 km s-1 and decreases with time. The ratio of He II to N III increases with time. The same is true for ASASSN-14li, which has a very similar spectrum to AT 2018dyb but its lines are narrower by a factor of &gt;2. We estimate a black hole mass of M BH = {3.3}-2.0+5.0× {10}6 M ☉ by using the M-σ relation. This is consistent with the black hole mass derived using the MOSFiT transient fitting code. The detection of strong Bowen lines in the optical spectrum is an indirect proof for extreme ultraviolet and (reprocessed) X-ray radiation and favors an accretion origin for the TDE optical luminosity. A model where photons escape after multiple scatterings through a super-Eddington thick disk and its optically thick wind, viewed at an angle close to the disk plane, is consistent with the observations.

Keywords: Supermassive black holes, Tidal disruption, Spectral line identification, Spectroscopy
Gamma-Ray Burst Host Galaxies: Specific Star Formation Rate versus Metallicity. The observed properties of long gamma-ray burst (GRB) host galaxies show them to often be of a rather low metallicity and/or of high specific star formation rate (SFR). It is not clear which of these properties is a dominant factor in determining if a galaxy will host a GRB or not. In fact there are indications, at least in the local universe, that the two may be anticorrelated and that the metallicity is the deciding parameter. Here, we consider GRB production models dependent on both quantities and show that when compared to the best available data, the respective star formation fractions appear indistinguishable out to a redshift of z ∼ 4. However, the fraction of galaxies hosting a GRB, as determined by the specific SFR, is less at tension with the observed host galaxy fraction than the corresponding metallicity determined fraction, but this conclusion is model dependent. Well established galaxy stellar mass and star formation rate functions at high redshift are crucial in breaking the apparent degeneracy between the specific rate and metallicity in GRB production probability.

Keywords: Star formation, Gamma-ray sources, High-redshift galaxies, Galaxy evolution