Sazuna/UAT_keywords huggingface dataset:
GASP. XXXII. Measuring the Diffuse Ionized Gas Fraction in Ram-pressure-stripped Galaxies. The diffuse ionized gas (DIG) is an important component of the interstellar medium, and it can be affected by many physical processes in galaxies. Measuring its distribution and contribution in emission allows us to properly study both its ionization and star formation in galaxies. Here, we measure for the first time the DIG emission in 38 gas-stripped galaxies in local clusters drawn from the GAs Stripping Phenomena in galaxies with the MUSE survey (GASP). These galaxies are at different stages of stripping. We also compare the DIG properties to those of 33 normal galaxies from the same survey. To estimate the DIG fraction (CDIG) and derive its maps, we combine the attenuation-corrected Hα surface brightness with the [S II]/Hα line ratio. Our results indicate that we cannot use either a single Hα or [S II]/Hα value, or a threshold in equivalent width of Hα emission line to separate spaxels dominated by DIG and non-DIG emission. Assuming a constant surface brightness of the DIG across galaxies underestimates CDIG. Contrasting stripped and nonstripped galaxies, we find no clear differences in CDIG. The DIG emission contributes between 20% and 90% of the total integrated flux and does not correlate with the galactic stellar mass and star formation rate (SFR). The CDIG anticorrelates with the specific SFR, which may indicate an older (&gt;108 yr) stellar population as the ionizing source of the DIG. The DIG fraction shows anticorrelations with the SFR surface density, which could be used for a robust estimation of integrated CDIG in galaxies.

Keywords: Galaxy clusters, Galaxy groups, Interstellar medium
Designing a New Coronal Magnetic Field Energy Diagnostic. In the solar corona, the free energy, i.e., the excess in magnetic energy over a ground-state potential field, forms the reservoir of energy that can be released during solar flares and coronal mass ejections. Such free energy provides a measure of the magnetic field nonpotentiality. Recent theoretical and observational studies indicate that the presence of nonpotential magnetic fields is imprinted into the structures of infrared, off-limb, coronal polarization. In this paper, we investigate the possibility of exploiting such observations for mapping and studying the accumulation and release of coronal free magnetic energy, with the goal of developing a new tool for identifying "hot spots" of coronal free energy such as those associated with twisted and/or sheared coronal magnetic fields. We applied forward modeling of infrared coronal polarimetry to three-dimensional models of nonpotential and potential magnetic fields. From these we defined a quantitative diagnostic of nonpotentiality that in the future could be calculated from a comparison of infrared, off-limb, coronal polarization observations from, e.g., the Coronal Multi-channel Polarimeter or the Daniel K. Inouye Solar Telescope, and the corresponding polarization signal forward-modeled from a potential field extrapolated from photospheric magnetograms. We considered the relative diagnostic potential of linear and circular polarization, and the sensitivities of these diagnostics to coronal density distributions and assumed boundary conditions of the potential field. Our work confirms the capacity of polarization measurements for diagnosing nonpotentiality and free energy in the solar corona.

Keywords: Infrared astronomy, Solar corona, Solar flares, Solar magnetic fields
A Cosmic Zevatron Based on Cyclotron Auto-resonance. A Zevatron is an accelerator scheme envisaged to accelerate particles to ZeV energies (1 ZeV = 1021 eV). Schemes, most notably the internal shock model, have been proposed to explain the acceleration of ultra-high-energy cosmic-ray particles that have been sporadically detected reaching Earth since 1962. Here, the cyclotron auto-resonance acceleration (CARA) mechanism is tailored and used to demonstrate the possible acceleration of particles ejected as a result of violent astrophysical processes such as the merger of a binary system or a supernova explosion. Such events result in emission of highly energetic particles and ultra-intense beamed radiation. In the simultaneous presence of a super-strong magnetic field, the condition for cyclotron auto-resonance may be met. Thus CARA can act like a booster for particles pre-accelerated inside their progenitor by shock waves, possibly among other means. As examples, it is shown that nuclei of hydrogen, helium, and iron-56, may reach ZeV energies by CARA, under which conditions the particles, while gyrating around the lines of an ultra-strong magnetic field, also surf on the waves of a super-intense radiation field. When radiation-reaction is taken into account, it is shown that the ZeV energy gained by a particle can fall off by less than an order of -magnitude if the resonance condition is missed by roughly less than 20%.

Keywords: Gamma-ray bursts, Compact radiation sources, Interstellar cyclotron emission, Cosmic ray sources, Compact objects, Ultra-high-energy cosmic radiation
A Search for Hard X-Ray Bursts Occurring Simultaneously with Fast Radio Bursts in the Repeating FRB 121102. The nature of fast radio bursts (FRBs) is currently unknown. Repeating FRBs offer better observation opportunities than nonrepeating FRBs because their simultaneous multiwavelength counterparts might be identified. The magnetar flare model of FRBs is one of the most promising models that predict high-energy emission in addition to radio burst emission. To investigate such a possibility, we have searched for simultaneous and quasi-simultaneous short-term hard X-ray bursts in all Swift/BAT event mode data, which covered the periods when FRB detections were reported in the repeating FRB 121102, by making use of BAT's arcminute-level spatial resolution and wide field of view. We did not find any significant hard X-ray bursts that occurred simultaneously with those radio bursts. We also investigated potential short X-ray bursts that occurred quasi-simultaneously with those radio bursts (occurrence time differs in the range from hundreds of seconds to thousands of seconds) and concluded that even the best candidates are consistent with background fluctuations. Therefore, our investigation concluded that there were no hard X-ray bursts detectable with Swift/BAT that occurred simultaneously or quasi-simultaneously with those FRBs in the repeating FRB 121102.

Keywords: Neutron stars, Radio bursts, X-ray transient sources, Non-thermal radiation sources, Magnetars, Radio transient sources
Modeling of Cosmic-Ray Production and Transport and Estimation of Gamma-Ray and Neutrino Emissions in Starburst Galaxies. Starburst galaxies (SBGs) with copious massive stars and supernova (SN) explosions are the sites of active cosmic-ray production. Based on the predictions of nonlinear diffusive shock acceleration theory, we model the cosmic-ray proton (CRP) production by both pre-SN stellar winds (SWs) and supernova remnants (SNRs) from core-collapse SNe inside the starburst nucleus. Adopting different models for the transport of CRPs, we estimate the nbsp;gamma;-ray and neutrino emissions due to pp collisions from nearby SBGs such as M82, NGC 253, and Arp 220. We find that with the current γ-ray observations by Fermi-LAT, Veritas, and H.E.S.S., it would be difficult to constrain CRP production and transport models. Yet, the observations are better reproduced with (1) the combination of a single power-law (PL) momentum distribution for SNR-produced CRPs and a diffusion model in which the CRP diffusion is mediated by the strong Kolmogorov-type turbulence of $\delta B/B\sim 1$ , and (2) the combination of a double-PL model for SNR-produced CRPs and a diffusion model in which the scattering of CRPs is controlled mostly by self-excited waves rather than the preexisting turbulence. The contribution of SW-produced CRPs could be substantial in Arp 220, where the star formation rate is higher and the slope of the initial mass function would be flatter. We suggest that M82 and NGC 253 might be detectable as point sources of high-energy neutrinos in the upcoming KM3NET and IceCube-Gen2, when optimistic models are applied. Future observations of neutrinos, as well as γ-rays, would provide constraints for the production and diffusion of CRPs in SBGs.

Keywords: Starburst galaxies, Neutrino astronomy, Supernova remnants, Stellar winds, Gamma-rays, Cosmic rays
THOR 42: A Test of Magnetic Models for Pre-main-sequence Stars. Precise masses and radii have been reported by Murphy et al. for the components of the THOR 42 binary. Murphy et al. provide evidence that, in their opinion, supports an earlier suggestion by Bell et al. that THOR 42 is a member of the 32 Ori moving group, which, according to Bell et al., has an age of about 24 Myr. From the positions of the THOR 2 components in the mass-radius diagram (MRD), Murphy et al. derive ages of 22-26 Myr using standard (nonmagnetic) models. However, they also find that these models cannot simultaneously reproduce the observed masses, radii, effective temperatures, and luminosities of the assumed coeval components. Their Hertzsprung-Russell diagram (HRD) ages are found to be 2-4 times younger than the MRD ages, and the masses determined from the HRD are found to be ∼50% smaller than the dynamical masses. Here, we attempt to replicate the precise global properties of THOR 24 by applying a model of magnetoconvection. We find that MRD isochrones and HRD isochrones lead to consistent ages provided that the surface magnetic fields have strengths of 300-400 G. However, the ages that our models yield for THOR 24 are in the vicinity of 40 Myr. If this age estimate is correct, it could call into question the membership of THOR 42 in the 32 Ori moving group.

Keywords: Eclipsing binary stars, Pre-main sequence stars, Stellar evolutionary models, Stellar magnetic fields
Phase Shift of Planetary Waves and Wave-Jet Resonance on Tidally Locked Planets. Recent studies found that atmospheric superrotation (i.e., west-to-east winds over the equator) on tidally locked planets can modify the phase of planetary waves. But a clear relationship between the superrotation and the magnitude of the phase shift was not examined. In this study, we re-investigate this problem using a 2D linear shallow-water model with a specified uniform zonal flow. We find that the degree of the phase shift is a monotonic but nonlinear function of the strength of the mean flow and the phase shift has two limits of -π and +π. The existence of these limits can be explained using the energy balance of the whole system. We further show that a resonance between the Rossby wave and the mean flow occurs when the speed of an eastward jet approaches to the westward phase speed of the Rossby wave, or a resonance between the Kelvin wave and the mean flow happens when the speed of a westward jet approaches to the eastward phase speed of the Kelvin wave. The resonance mechanism is the same as that found in the previous studies on Earth and hot Jupiters. Moreover, in the spin-up period of a 3D global atmospheric general circulation simulation for tidally locked rocky planet, we also find these two phenomena: phase shift and wave-jet resonance. This study improves the understanding of wave-mean-flow interactions on tidally locked planets.

Keywords: Exoplanets, Earth atmosphere, Atmospheric circulation, Planetary atmospheres, Analytical mathematics, Transit photometry, Exoplanet atmospheres, Atmospheric science
Resolving the Dust-to-Metals Ratio and CO-to-H<SUB>2</SUB> Conversion Factor in the Nearby Universe. We investigate the relationship between the dust-to-metals ratio (D/M) and the local interstellar medium environment at ∼2 kpc resolution in five nearby galaxies: IC 342, M31, M33, M101, and NGC 628. A modified blackbody model with a broken power-law emissivity is used to model the dust emission from 100 to 500 μm observed by Herschel. We utilize the metallicity gradient derived from auroral line measurements in H I regions whenever possible. Both archival and new CO rotational line and H I 21 cm maps are adopted to calculate gas surface density, including new wide-field CO and H I maps for IC 342 from IRAM and the VLA, respectively. We experiment with several prescriptions of the CO-to-H2 conversion factor and compare the resulting D/M-metallicity and D/M-density correlations, both of which are expected to be nonnegative from depletion studies. The D/M is sensitive to the choice of the conversion factor. The conversion factor prescriptions based on metallicity only yield too much molecular gas in the center of IC 342 to obtain the expected correlations. Among the prescriptions tested, the one that yields the expected correlations depends on both metallicity and surface density. The 1σ range of the derived D/M spans 0.40-0.58. Compared to chemical evolution models, our measurements suggest that the dust growth timescale is much shorter than the dust destruction timescale. The measured D/M is consistent with the D/M in galaxy-integrated studies derived from infrared dust emission. Meanwhile, the measured D/M is systematically higher than the D/M derived from absorption, which likely indicates a systematic offset between the two methods.

Keywords: Interstellar dust, Molecular gas, Dust continuum emission, Interstellar dust processes, Metallicity
Cloudy Atmospheres on Directly Imaged Exoplanets: The Need for Accurate Particulate Representation in Photopolarimetric Simulations. Missions like the upcoming Roman Space Telescope and its follow-on missions, Habitable Exoplanet Observatory (HabEx) and the Large UV/Optical/IR Surveyor (LUVOIR), will provide direct imaging observations of stellar light reflected by exoplanets with successively closer orbits. The synergistic use of ground-based polarimeters like Gemini Planet Imager and Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet Research instrument (SPHERE) would allow us to characterize cloudy exoplanet atmospheres using spectropolarimetric direct imaging. We present an extension of our semianalytic 3D radiative transfer modeling framework for brown dwarfs to include stellar light reflected by exoplanets with cloudy atmospheres. Using Mie theory to compute scattering by cloud and haze consisting of spherical particles, we show that the currently widespread use of approximations like the scalar Two-Term Henyey-Greenstein or the vector Henyey-Greenstein Rayleigh (HGR) composite result in a blurring of the phase-dependent features of exoplanet lightcurves, causing a 10%-39% loss of sensitivity to atmospheric parameters in an average measurement for signal-to-noise ratios (S/Ns) between 5 and 500. The HGR approximation creates the misleading impression that clouds are as polarizing as Rayleigh scatterers, regardless of their droplet size. This not only causes significant errors in the scientific interpretation of polarimetric measurements, but also results in a negligible sensitivity of HGR simulations to polarization measurements at the S/Ns considered, whereas Mie simulations show a 10%-30% gain in parametric sensitivity through the addition of polarimetry.

Keywords: Exoplanet atmospheric composition , Earth's clouds, Direct imaging, Atmospheric composition, Polarimetry
Testing the Kerr Black Hole Hypothesis with GX 339-4 by a Combined Analysis of Its Thermal Spectrum and Reflection Features. We analyze simultaneous observations with NuSTAR and Swift of the black hole binary GX 339-4 in which we clearly detect both a strong thermal component and prominent relativistic reflection features. We employ nkbb and relxill_nk, which are the state of the art of, respectively, the thermal and reflection models to test the Kerr black hole hypothesis. We obtain unprecedented precise measurements of the Johannsen deformation parameter α13: ${\alpha }_{13}=-{0.012}_{-0.039}^{+0.011}$ (lamppost coronal geometry) and ${\alpha }_{13}=-{0.010}_{-0.018}^{+0.024}$ (broken power-law emissivity profile) at a 90% confidence level, where the Kerr metric corresponds to α13 = 0. We investigate the systematic uncertainties by fitting the data with different models.

Keywords: X-ray astronomy, Stellar mass black holes, Kerr metric, Astrophysical black holes
The Coma Cluster at LOw Frequency ARray Frequencies. I. Insights into Particle Acceleration Mechanisms in the Radio Bridge. Radio synchrotron emission from the bridges of low-density gas connecting galaxy clusters and groups is a challenge for particle acceleration processes. In this work, we analyze the Coma radio bridge using new LOw Frequency ARray (LOFAR) observations at 144 MHz. LOFAR detects the bridge and its substructures with unprecedented sensitivity and resolution. We found that the radio emission peaks on the NGC 4839 group. Toward the halo, in front of the NGC 4839 group, the radio brightness decreases and streams of radio emission connect the NGC 4839 group to the radio relic. Using X-ray observations, we found that thermal and non-thermal plasma are moderately correlated with a sublinear scaling. We use archival radio data at 326 MHz to constrain the spectral index in the bridge, and quantify the distribution of particles and magnetic field at different frequencies. We found that the spectrum is steeper than -1.4 ± 0.2, and that the emission is clumpier at 326 MHz than at 144 MHz. Using cosmological simulations and a simplified approach to compute particle acceleration, we derive under which conditions turbulent acceleration of mildly relativistic electrons generate the radio emission in the bridge. Assuming that the initial energy ratio of the seed electrons is 3 · 10-4 with respect to the thermal gas, we are able to reproduce the observed luminosity. Our results suggest that the seed electrons released by radio galaxies in the bridge and the turbulence generated by the motion of gas and galaxies are essential to producing the radio emission.

Keywords: Galaxy clusters, Plasma astrophysics, Coma Cluster, Intergalactic medium, Radio continuum emission, Intracluster medium, Extragalactic magnetic fields
The JCMT BISTRO Survey: Alignment between Outflows and Magnetic Fields in Dense Cores/Clumps. We compare the directions of molecular outflows of 62 low-mass Class 0 and I protostars in nearby (&lt;450 pc) star-forming regions with the mean orientations of the magnetic fields on 0.05-0.5 pc scales in the dense cores/clumps where they are embedded. The magnetic field orientations were measured using the JCMT POL-2 data taken by the BISTRO-1 survey and from the archive. The outflow directions were observed with interferometers in the literature. The observed distribution of the angles between the outflows and the magnetic fields peaks between 15° and 35°. After considering projection effects, our results could suggest that the outflows tend to be misaligned with the magnetic fields by 50° ± 15° in three-dimensional space and are less likely (but not ruled out) randomly oriented with respect to the magnetic fields. There is no correlation between the misalignment and the bolometric temperatures in our sample. In several sources, the small-scale (1000-3000 au) magnetic field is more misaligned with the outflow than the large-scale magnetic field, suggesting that the small-scale magnetic field has been twisted by the dynamics. In comparison with turbulent MHD simulations of core formation, our observational results are more consistent with models in which the energy densities in the magnetic field and the turbulence of the gas are comparable. Our results also suggest that the misalignment alone cannot sufficiently reduce the efficiency of magnetic braking to enable formation of the observed number of large Keplerian disks with sizes larger than 30-50 au.

Keywords: Interstellar magnetic fields, Protostars, Star forming regions, Star formation
Observations of the Disk/Jet Coupling of MAXI J1820+070 during Its Descent to Quiescence. Black hole X-ray binaries in the quiescent state (Eddington ratios typically ≲10-5) display softer X-ray spectra (photon indices Γ ∼ 2) compared to higher-luminosity black hole X-ray binaries in the hard state (Γ ∼ 1.7). However, the cause of this softening and its implications for the underlying accretion flow are still uncertain. Here, we present quasi-simultaneous X-ray and radio spectral monitoring of the black hole X-ray binary MAXI J1820+070 during the decay of its 2018 outburst and of a subsequent reflare in 2019, providing an opportunity to monitor a black hole X-ray binary as it actively transitions into quiescence. We probe 1-10 keV X-ray luminosities as low as LX ∼ 4 × 1032 erg s-1, equivalent to Eddington fractions of ∼4 × 10-7. During its decay toward quiescence, the X-ray spectrum of MAXI J1820+070 softens from Γ ∼ 1.7 to Γ ∼ 2, with the softening taking ∼30 days and completing at LX ≈ 1034 erg s-1 (≈10-5 LEdd). While the X-ray spectrum softens, the radio spectrum generally remains flat or inverted throughout the decay. We also find that MAXI J1820+070 follows a radio (LR)-X-ray luminosity correlation of the form LR ∝ LX0.52±0.07, making it the fourth black hole system to follow the so-called "standard track" unbroken over several (in this case, four) decades in LX. Comparing the radio/X-ray spectral evolution(s) with the LR-LX plane, we find that the X-ray softening is consistent with X-rays produced by Comptonization processes in a radiatively inefficient accretion flow. We generally disfavor X-ray emission originating solely from within the jet, with the possible exception of X-rays produced via synchrotron self-Compton processes.

Keywords: Accretion, X-ray transient sources, Low-mass x-ray binary stars, Black holes
Strongly Lensed Supernova Refsdal: Refining Time Delays Based on the Supernova Explosion Models. We explore the properties of supernova (SN) "Refsdal"—the first discovered gravitationally lensed SN with multiple images. A large magnification provided by the galactic-scale lens, augmented by the cluster lens, gave us a unique opportunity to perform a detailed modeling of a distant SN at $z\simeq 1.5$ . We present results of radiation hydrodynamics modeling of SN Refsdal. According to our calculations, the SN Refsdal progenitor is likely to be a more massive and energetic version of SN 1987A, i.e., a blue supergiant star with the following parameters: the progenitor radius ${R}_{0}=(50\pm 1){R}_{\odot }$ , the total mass ${M}_{\mathrm{tot}}=(25\pm 2){M}_{\odot }$ , the radioactive 56Ni mass ${M}_{{}^{56}\mathrm{Ni}}=(0.26\pm 0.05)\,{M}_{\odot }$ , and the total energy release ${E}_{\mathrm{burst}}=(4.7\pm 0.8)\times {10}^{51}$ erg. Reconstruction of SN light curves allowed us to obtain time delays and magnifications for the images S2-S4 relative to S1 with higher accuracy than previous template-based estimates of Rodney et al. (2016). The measured time delays are ${\rm{\Delta }}{t}_{S2-S1}={9.5}_{-2.7}^{+2.6}$ days, ${\rm{\Delta }}{t}_{S3-S1}={4.2}_{-2.3}^{+2.3}$ days, and ${\rm{\Delta }}{t}_{S4-S1}={30}_{-8.2}^{+7.8}$ days. The obtained magnification ratios are ${\mu }_{S2/S1}=1.14\pm 0.02$ , ${\mu }_{S3/S1}=1.01\pm 0.02$ , and ${\mu }_{S4/S1}=0.35\pm 0.02$ . We estimate the Hubble constant ${H}_{0}={68.6}_{-9.7}^{+13.6}$ km s-1 Mpc-1 via rescaling the time delays predicted by different lens models to match the values obtained in this work. With more photometric data on the fifth image SX, we will be able to further refine the time delay and magnification estimates for SX and obtain competitive constraints on H0.

Keywords: Galaxy clusters, Type II supernovae, Strong gravitational lensing