Sazuna/UAT_keywords huggingface dataset:
Galaxy Mergers up to z &lt; 2.5. II. AGN Incidence in Merging Galaxies at Separations of 3-15 kpc. We present a study of the incidence of active galactic nucleus (AGN) in a sample of major merging systems at 0.3 &lt; z &lt; 2.5. Galaxies in this merger sample have projected separations between 3 and 15 kpc and are selected from the CANDELS/3D-Hubble Space Telescope catalogs using a peak-finding algorithm. AGNs in mergers and non-mergers are identified on the basis of their X-ray emission, optical lines, mid-infrared colors, and radio emission. Among galaxies with adequate measurements to find potential AGNs, we find a similar fraction of AGNs in mergers (16.4 ${\pm }_{3.1}^{5.0}$ %) compared to the fraction found in non-merging galaxies (15.4% ± 0.6%). In mergers, this fraction is obtained by assuming that, in unresolved observations, only one of the merging galaxies is the AGN source (16 merging systems have at least one AGN galaxy). The similarity between the fractions is possibly due to the higher availability of cold gas at high redshifts, where the excess of nuclear activity as a result of merging is less important than at lower redshifts. Star-forming galaxies have a higher incidence of AGNs than quiescent galaxies. In particular, starbursts in mergers are the most common sites of AGN activity, since they present higher AGN fractions and black hole accretion rates. We find no clear correlation between the black hole accretion rate and the galaxy properties (i.e., star formation rate, stellar mass) in mergers and non-mergers. However, mergers seem to have a higher correlation with star formation than non-mergers, which possibly indicates that the merging process is starting to influence the star formation and AGN activity even at this pre-coalescence stage.

Keywords: Galaxy formation, Galaxy interactions, Galaxy pairs, Active galaxies, Active galactic nuclei, Galaxy evolution, Galaxy mergers, High-redshift galaxies
Buckling Bars in Nearly Face-on Galaxies Observed with MaNGA. Over half of disk galaxies are barred, yet the mechanisms for bar formation and the lifetime of bar buckling remain poorly understood. In simulations, a thin bar undergoes a rapid (&lt;1 Gyr) event called "buckling," during which the inner part of the bar is asymmetrically bent out of the galaxy plane and eventually thickens, developing a peanut/X-shaped profile when viewed side-on. Through analyzing stellar kinematics of N-body model snapshots of a galaxy before, during, and after the buckling phase, we confirm a distinct quadrupolar pattern of out-of-plane stellar velocities in nearly face-on galaxies. This kinematic signature of buckling allows us to identify five candidates of currently buckling bars among 434 barred galaxies in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Survey, an integral field unit spectroscopic survey that measures the composition and kinematic structure of nearby galaxies. The frequency of buckling events detected is consistent with the 0.5-1 Gyr timescale predicted by simulations. The five candidates we present more than double the total number of candidate buckling bars and are the only ones found using the kinematic signature.

Keywords: Galaxy structure, Barred spiral galaxies, Galaxy kinematics
Swift Follow-up Observations of Gravitational-wave and High-energy Neutrino Coincident Signals. Electromagnetic observations of gravitational-wave and high-energy neutrino events are crucial in understanding the physics of their astrophysical sources. X-ray counterparts are especially useful in studying the physics of the jet, the energy of the outflow, and the particle acceleration mechanisms in the system. Ultraviolet and optical observations can help us constrain the mass and velocity of the outflow and provide hints on the viewing angle. We present the Neil Gehrels Swift Observatory prompt searches for X-ray and UV/optical counterparts to the joint gravitational-wave and high-energy neutrino coincident events that happened during the third observing run of LIGO/Virgo. Swift observed the overlap between gravitational-wave and neutrino error regions for three of the considerable (p-value &lt; 1%) joint gravitational-wave and high-energy neutrino coincident alerts, which were generated by the IceCube Neutrino Observatory in real time after triggering by the LIGO/Virgo gravitational-wave public alerts. The searches did not associate any X-ray or UV/optical counterparts with any of the joint gravitational-wave and high-energy neutrino coincident events; however, the follow-up of these alerts significantly improved the tiling techniques covering regions between the gravitational-wave sky maps and the neutrino's error regions, making the real-time system ready for future potential discoveries. We discuss the details of each follow-up procedure, the results of each search, and the plans for future searches.

Keywords: X-ray astronomy, Cosmological neutrinos, Gravitational waves, X-ray sources, Particle astrophysics
Relationship between Polytropic Index and Temperature Anisotropy in Space Plasmas. The paper develops a theoretical relationship between the polytropic index and the temperature anisotropy that may characterize space plasmas. The derivation is based on the correlation among the kinetic energies of particles with velocities described by anisotropic kappa distributions. The correlation coefficient depends on the effective dimensionality of the velocity distribution, which is determined by the temperature anisotropy caused by the ambient magnetic field; on the other hand, the effective dimensionality is directly dependent on the polytropic index. This analysis leads to the connection between the correlation coefficient, effective dimensionality of the velocity space, and the polytropic index, with the temperature anisotropy. Moreover, a data and statistical analysis is performed to test the developed model in the solar wind proton plasma near 1 au. The derived theoretical relationship is in good agreement with observations, showing that the lowest and classical value of the adiabatic polytropic index occurs in the isotropic case, while higher values of the adiabatic index characterize more anisotropic plasmas. Finally, possible extensions of the theory considering (i) nonadiabatic polytropic behavior and (ii) more general distributions, are further discussed.

Keywords: Slow solar wind, Space plasmas, Heliosphere, Solar wind, Plasma astrophysics, Astronomy data analysis
Influence of Biomass Emissions on Habitability, Biosignatures, and Detectability in Earth-like Atmospheres. We investigate the atmospheric responses of modeled hypothetical Earth-like planets in the habitable zone of the M-dwarf AD Leonis to reduced oxygen (O2), removed biomass ("dead" Earth), and varying carbon dioxide (CO2) and surface relative humidity (sRH). Results suggest large O2 differences between the reduced-O2 and dead scenarios in the lower but not the upper atmosphere layers. Ozone (O3) and nitrous oxide (N2O) also show this behavior. Methane depends on hydroxyl (OH), its main sink. Abiotic production of N2O occurs in the upper layers. Chloromethane (CH3Cl) decreases everywhere on decreasing biomass. Changing CO2 (from ×1 to ×100 present atmospheric levels (PALs)) and sRH (from 0.1% to 100%) does not influence CH3Cl as much as lowering biomass. Therefore, CH3Cl can be considered a good biosignature. Changing sRH and CO2 has a greater influence on temperature than changing O2 or biomass alone. Changing the biomass produces an ∼6 km effective height in transmission compared with changing CO2 and sRH (∼25 km). In transmission O2 is discernible at 0.76 μm for &gt;0.1 PAL. The O3 9.6 μm band is weak for the low-O2 runs and difficult to discern from dead Earth; however O3 at 0.3 μm could serve as an indicator to distinguish between reduced-O2 and dead Earth. The spectral features of N2O and CH3Cl correspond to effective heights of a few kilometers. CH4 could be detectable tens of parsecs away with the Extremely Large Telescope except for the 10-4 and 10-6 PAL O2 scenarios. O2 is barely detectable for the 1 PAL O2 case and unfeasible at lower abundances.

Keywords: Exoplanet atmospheres
The HectoMAP Redshift Survey: First Data Release. HectoMAP is a dense, red-selected redshift survey to a limiting r = 21.3 mag covering 55 deg2 in a contiguous 1°5 strip across the northern sky. This region is also covered by the Subaru/Hyper Suprime-Cam (HSC) Subaru Strategic Program photometric survey enabling a range of applications that combine a dense foreground redshift survey with both strong and weak lensing maps. The median redshift of HectoMAP exceeds 0.3 throughout the survey region, and the mean density of the redshift survey is ∼2000 galaxies deg-2. Here we report a total of 17,313 redshifts in a first data release covering 8.7 deg2. We include the derived quantities Dn4000 and stellar mass for nearly all of the objects. Among these galaxies, 8117 constitute a 79% complete red-selected subsample with r ≤ 20.5 mag, and an additional 4318 constitute a 68% complete red-selected subsample with 20.5 &lt; r(mag) &lt; 21.3. As examples of the strengths of HectoMAP data, we discuss two applications: refined membership of redMaPPer photometrically selected clusters and a test of HSC photometric redshifts. We highlight a remarkable redMaPPer strong lensing system. The comparison of photometric redshifts with spectroscopic redshifts in a dense survey uncovers subtle systematic issues in the photometric redshifts.

Keywords: Galaxy clusters, Redshift surveys, Large-scale structure of the universe
Ultrafaint [C II] Emission in a Redshift = 2 Gravitationally Lensed Metal-poor Dwarf Galaxy. Extreme emission-line galaxies (EELGs) at redshift z = 1-2 provide a unique view of metal-poor, starburst sources that are the likely drivers of the cosmic reionization at z ≥ 6. However, the molecular gas reservoirs of EELGs—the fuel for their intense star formation—remain beyond the reach of current facilities. We present ALMA [C II] and PdBI CO(2-1) observations of the z = 1.8, strongly lensed EELG SL2S 0217, a bright Lyα emitter with a metallicity 0.05 Z⊙. We obtain a tentative (∼3σ-4σ) detection of the [C II] line and set an upper limit on the [C II]/SFR (star-forming rate) ratio of ≤1 × 106 L⊙/(M⊙ yr-1), based on the synthesized images and visibility-plane analysis. The CO(2-1) emission is not detected. Photoionization modeling indicates that up to 80% of the [C II] emission originates from neutral or molecular gas, although we cannot rule out that the gas is fully ionized. The very faint [C II] emission is in line with both nearby metal-poor dwarfs and high-redshift Lyα emitters, and predictions from hydrodynamical simulations. However, the [C II] line is 30× fainter than predicted by the De Looze et al. [C II]-SFR relation for local dwarfs, illustrating the danger of extrapolating locally calibrated relations to high-redshift, metal-poor galaxies.

Keywords: Dwarf galaxies, Gravitational lensing, Lyman-alpha galaxies, Submillimeter astronomy, High-redshift galaxies
SDSS-IV MaNGA: A Star Formation-Baryonic Mass Relation at Kiloparsec Scales. Star formation rate density, ΣSFR, has shown a remarkable correlation with both components of the baryonic mass kiloparsec scales (i.e., the stellar mass density and molecular gas mass density, Σ* and Σmol, respectively) for galaxies in the nearby universe. In this study, we propose an empirical relation between ΣSFR and the baryonic mass surface density (Σb = Σmol,Av + Σ*, where Σmol,Av is the molecular gas derived from the optical extinction, AV) at kiloparsec scales using the spatially resolved properties of the MaNGA survey, the largest sample of galaxies observed via integral field spectroscopy (∼8400 objects). We find that ΣSFR tightly correlates with Σb. Furthermore, we derive an empirical relation between ΣSFR and a second-degree polynomial of Σb, yielding a one-to-one relation between these two observables. Both Σb and its polynomial form show a stronger correlation and smaller scatter with respect to ΣSFR than the relations derived using the individual components of Σb. Our results suggest that these three parameters are indeed physically correlated, suggesting a scenario in which the two components of the baryonic mass regulate the star formation activity at kiloparsec scales.

Keywords: Spiral galaxies, Disk galaxies, Surveys, Star forming regions, Scaling relations
Detection of Dust Particles Using Faraday Cup Instruments. Faraday cups can measure velocity distribution functions of space plasmas and are frequent instruments on heliophysics missions. A new version of a Faraday cup instrument is in development for the Luna 26 mission and will be used for fast monitoring of the solar wind plasma parameters. The prototype of this instrument is exposed to dust impacts in a velocity range of 0.2-60 km s-1 using an electrostatic dust accelerator. The collected data are used to evaluate the sensitivity and detection efficiency of dust particles on two different surfaces. The results indicate that the sensitivity is sufficient for detection of the interplanetary dust as well as for the registration of the dust lifted from the lunar surface. A simple modification of the FC electronics would increase the detection efficiency by an order of magnitude.

Keywords: Interstellar dust, Interplanetary dust, Solid matter physics
The Photospheric Footpoints of Solar Coronal Hole Jets. We study the photospheric footpoints of a set of 35 coronal jets in a coronal hole as observed by Hinode/EIS. We use SDO/AIA data to coalign the spectroscopic EIS data with SDO/HMI line-of-sight magnetograms and calculate the plane-of-sky flow field using local correlation tracking (LCT) on SDO/HMI white light images. The jets are put into categories according to the changes observed in the photospheric magnetic flux at the footpoints of the coronal bright point where the jets originate: flux cancellation, complex flux changes (flux appearance/emergence and cancellation), and no flux changes. We also present three jets in detail. Observed magnetic flux evolution, LCT flow field structure and location of the jet footpoints at supergranular boundaries do not support the flux emergence scenario used in most jet simulations and are also not consistent with a rotational photospheric driver. Detailed numerical jet simulations using our observed photospheric features, in particular converging flows and flux cancellation do not currently exist, although such models would provide a realistic eruptive event scenario.

Keywords: Solar coronal transients, Solar atmospheric motions, Solar photosphere, Solar ultraviolet emission, Solar magnetic reconnection, Solar physics, Eruptive phenomena, Solar magnetic fields, Solar corona, Solar coronal holes, Solar magnetic bright points
Exact Theory of Nonrelativistic Quadrupole Bremsstrahlung. The quantum mechanical treatment of quadrupole radiation due to bremsstrahlung exact to all orders in the Coulomb interaction of two nonrelativistically colliding charged spin-0 and unpolarized spin-1/2 particles is presented. We calculate the elements of the quadrupole tensor, and present analytical solutions for the double-differential photon emission cross section of identical and nonidentical particles. Contact is made to Born-level and quasi-classical results in the respective kinematic limits and effective energy loss rates are obtained. A generally valid formula for soft-photon emission is established and an approximate formula across the entire kinematic regime is constructed. The results apply to bremsstrahlung emission in the scattering of pairs of electrons and are hence relevant in the study of astrophysical phenomena. A definition of a Gaunt factor is proposed which should facilitate broad applicability of the results.

Keywords: Interstellar thermal emission, Interstellar emissions, Interstellar medium
Particle Dynamics in 3D Self-gravitating Disks. I. Spirals. Spiral arms are distinctive features of many circumstellar disks, observed in scattered light, which traces the disk surface; millimeter dust emission, which probes the disk midplane; as well as molecular emission. The two leading explanations for spirals are wakes generated by a massive planet and the density waves excited by disk self-gravity. We use stratified 3D hydrodynamic shearing-box simulations including dust particles and disk self-gravity to investigate how gas and dust spirals in a self-gravitating disk depend on the simulation size, the cooling efficiency, and the aerodynamic properties of particles. We find that the opening angles of spirals are universal (∼10°) and not significantly affected by the size of the computational domain, the cooling time, or the particle size. In simulations with the biggest domain, the spirals in the gaseous disk become slightly more open with a higher cooling efficiency. Small dust follows the gaseous spirals very well, while intermediate-sized dust with dimensionless stopping time (St) close to 1 is more concentrated in the spirals and shows stronger spirals. However, large dust with St &gt; 1 also shows spirals, which is different from some previous simulations. We identify that this is due to the gravity from the gas to the dust component. We show that when St ≳ Q, the gravitational force from the gaseous spirals on the dust particles becomes stronger than the particles' aerodynamic drag force, so that the gas significantly affects these large particles through gravitational interaction. This has important implications for both spiral observations and planetesimal formation/dynamics.

Keywords: Gravitation, Circumstellar dust, Protoplanetary disks, Hydrodynamics
Particle Dynamics in 3D Self-gravitating Disks. II. Strong Gas Accretion and Thin Dust Disks. Observations suggest that protoplanetary disks have moderate accretion rates onto the central young star, especially at early stages (e.g., HL Tau), indicating moderate disk turbulence. However, recent ALMA observations suggest that dust is highly settled, implying weak turbulence. Motivated by such tension, we carry out 3D stratified local simulations of self-gravitating disks, focusing on the settling of dust particles in actively accreting disks. We find that gravitationally unstable disks can have moderately high accretion rates while maintaining a relatively thin dust disk for two reasons. First, accretion stress from the self-gravitating spirals (self-gravity stress) can be stronger than the stress from turbulence (Reynolds stress) by a factor of 5-20. Second, the strong gravity from the gas to the dust decreases the dust scale height by another factor of ∼2. Furthermore, the turbulence is slightly anisotropic, producing a larger Reynolds stress than the vertical dust diffusion coefficient. Thus, gravitoturbulent disks have unusually high vertical Schmidt numbers (Scz) if we scale the total accretion stress with the vertical diffusion coefficient (e.g., Scz ∼ 10-100). The reduction of the dust scale height by the gas gravity should also operate in gravitationally stable disks (Q &gt; 1). Gravitational forces between particles become more relevant for the concentration of intermediate dust sizes, forming dense clouds of dust. After comparing with HL Tau observations, our results suggest that self-gravity and gravity among different disk components could be crucial for solving the conflict between the protoplanetary disk accretion and dust settling, at least at the early stages.

Keywords: Gravitation, Circumstellar dust, Protoplanetary disks, Hydrodynamics
Exact Semianalytical Calculation of Rotation Curves with Bekenstein-Milgrom Nonrelativistic MOND. Astronomers derive MOdified Newtonian Dynamics (MOND) rotation curves using the simple algebraic rule of calculating the acceleration as equal to the Newtonian acceleration (a) divided by some factor μ(a). However, there are velocity differences between this simple rule and the calculation derived from more sophisticated MOND versions such as AQUAL or QMOND, created to expand MOND heuristic law and preserve the conservation of momentum, angular momentum, and energy, and follow the weak equivalence principle. Here we provide recipes based on Milgrom's proposal to calculate semianalytically (without numerical simulations) MOND rotation curves for any density distribution based on AQUAL, applying it to different models of thin disks. The application of this formalism is equivalent to the creation of a fictitious phantom mass whose field may be used in a Newtonian way to calculate iteratively the MOND accelerations. In most cases, the differences between the application of the simple algebraic rule and the AQUAL-MOND calculations are small, ≲5%. However, the error of the algebraic solution is larger than 5% when more than half of the mass is in the MONDian regime (where Newtonian and MOND rotation speeds differ by more than 10%), reaching in some cases &gt;70% discrepancy, such as in Maclaurin disks, representative of galaxies for which the rotational velocity rises to the edge of the disk as is seen in irregular galaxies. The slope of the rotation speed in the dependence with the radius or the vertical distance of the plane is also significantly changed.

Keywords: Galaxy dynamics, Spiral galaxies
Multiwavelength Observations of the RV Tauri Variable System U Monocerotis: Long-term Variability Phenomena That Can Be Explained by Binary Interactions with a Circumbinary Disk. We present an X-ray through submillimeter observations of the classical RV Tauri (RVb-type) variable U Mon, a post-asymptotic giant branch (AGB) binary with a circumbinary disk (CBD). Our SMA observations indicate a CBD diameter of ≲550 au. Our XMM-Newton observations make U Mon the first RV Tauri variable detected in X-rays. The X-ray emission is characteristic of a hot plasma (∼10 MK), with LX =5 × 1030 erg s-1, and we consider its possible origin from U Mon, its companion, and/or binary system interactions. Combining DASCH and AAVSO data, we extend the time-series photometric baseline back to the late 1880s and find evidence that U Mon has secular changes that appear to recur on a timescale of ∼60 yr, possibly caused by a feature in the CBD. From literature radial velocities we find that the binary companion is a ∼2 M☉ A-type main-sequence star. The orientation of the binary's orbit lies along our line of sight (ω = 95°), such that apastron corresponds to photometric RVb minima, consistent with the post-AGB star becoming obscured by the near side of the CBD. In addition, we find the size of the inner-CBD hole (∼4.5-9 au) to be comparable to the binary separation, implying that one or both stars may interact with the CBD at apastron. The obscuration of the post-AGB star implicates the companion as the likely source of the enhanced Hα observed at RVb minima and of the X-ray emission that may arise from accreted material.

Keywords: X-ray astronomy, Binary stars, Post-asymptotic giant branch stars, Circumstellar matter, Spectral energy distribution, Submillimeter astronomy, RV Tauri variable stars