Sazuna/UAT_keywords huggingface dataset:
The Universe is Brighter in the Direction of Our Motion: Galaxy Counts and Fluxes are Consistent with the CMB Dipole. An observer moving with respect to the cosmic rest frame should observe a concentration and brightening of galaxies in the direction of motion and a spreading and dimming in the opposite direction. The velocity inferred from this dipole should match that of the cosmic microwave background (CMB) temperature dipole if galaxies are on average at rest with respect to the CMB rest frame. However, recent studies have claimed a many-fold enhancement of galaxy counts and flux in the direction of the solar motion compared to the CMB expectation, calling into question the standard cosmology. Here we show that the sky distribution and brightness of extragalactic radio sources are consistent with the CMB dipole in direction and velocity. We use the first epoch of the Very Large Array Sky Survey combined with the Rapid Australian Square Kilometer Array Pathfinder Continuum Survey to estimate the dipole via several different methods, and all show similar results. Typical fits find a ${331}_{-107}^{+161}$ km s-1 velocity dipole with apex $({\ell },b)=({271}_{-58}^{+55},{56}_{-35}^{+13})$ in Galactic coordinates from source counts and ${399}_{-199}^{+264}$ km s-1 toward $({\ell },b)=({301}_{-30}^{+30},{43}_{-17}^{+19})$ from radio fluxes. These are consistent with the CMB-solar velocity, 370 km s-1 toward (ℓ, b) = (264, 48), and show that galaxies are on average at rest with respect to the rest frame of the early universe, as predicted by the canonical cosmology.

Keywords: Cosmological models, Radio source catalogs, Extragalactic radio sources, Observational cosmology, Special relativity, Cosmic anisotropy, Relativistic cosmology, Relativistic aberration, Radio source counts, Solar motion
Ellipsars: Ring-like Explosions from Flattened Stars. The stellar cataclysms producing astronomical transients have long been modeled as either a point-like explosion or jet-like engine ignited at the center of a spherically symmetric star. However, many stars are observed, or are expected on theoretical grounds, not to be precisely spherically symmetric, but rather to have a slightly flattened geometry similar to that of an oblate spheroid. Here we present axisymmetric two-dimensional hydrodynamical simulations of the dynamics of point-like explosions initiated at the center of an aspherical massive star with a range of oblateness. We refer to these exploding aspherical stars as "ellipsars" in reference to the elliptical shape of the isodensity contours of their progenitors in the two-dimensional axisymmetric case. We find that ellipsars are capable of accelerating expanding rings of relativistic ejecta. which may lead to the production of astronomical transients including low-luminosity gamma-ray bursts, relativistic supernovae, and fast blue optical transients

Keywords: Supernovae, Gamma-ray bursts, Transient sources, Relativistic fluid dynamics
Solar-like Dynamos and Rotational Scaling of Cycles from Star-in-a-box Simulations. Magnetohydrodynamic star-in-a-box simulations of convection and dynamos in a solar-like star with different rotation rates are presented. These simulations produce solar-like differential rotation with a fast equator and slow poles and magnetic activity that resembles that of the Sun with equatorward migrating activity at the surface. Furthermore, the ratio of rotation to cycle period is almost constant, as the rotation period decreases in the limited sample considered here. This is reminiscent of the suggested inactive branch of stars from observations and differs from most earlier simulation results from spherical shell models. While the exact excitation mechanism of the dynamos in the current simulations is not yet clear, it is shown that it is plausible that the greater freedom that the magnetic field has due to the inclusion of the radiative core and regions exterior to the star are important in shaping the dynamo.

Keywords: Astrophysical fluid dynamics, Stellar magnetic fields, Magnetohydrodynamical simulations
Neutrino Mass Bounds in the Era of Tension Cosmology. The measurements of cosmic microwave background (CMB) anisotropies made by the Planck satellite provide extremely tight upper bounds on the total neutrino mass scale (Σm  ν  &lt; 0.26 eV at 95% C.L.). However, as recently discussed in the literature, the Planck data show anomalies that could affect this result. Here we provide new constraints on neutrino masses using the recent and complementary CMB measurements from the Atacama Cosmology Telescope DR4 and the South Pole Telescope SPT-3G experiments. We found that both the ACT-DR4 and SPT-3G data, when combined with WMAP, mildly suggest a neutrino mass with Σm  ν  = 0.68 ± 0.31 and ${0.46}_{-0.36}^{+0.14}$ eV at 68% C.L., respectively. Moreover, when CMB lensing from the Planck experiment is included, the ACT-DR4 data now indicate a neutrino mass above the two standard deviations, with ${\rm{\Sigma }}{m}_{\nu }={0.60}_{-0.50}^{+0.44}$ eV at 95% C.L., while WMAP+SPT-3G provides a weak upper limit of Σm  ν  &lt; 0.37 eV at 68% C.L. Interestingly, these results are consistent with the Planck CMB+lensing constraint of ${\rm{\Sigma }}{m}_{\nu }={0.41}_{-0.25}^{+0.17}$ eV at 68% C.L. when variations in the A lens parameter are considered. We also show that these indications are still present after the inclusion of BAO or Type Ia supernova data in extended cosmologies that are usually considered to solve the so-called Hubble tension. In this respect, we note that in these models, CMB+BAO constraints prefer a higher neutrino mass for higher values of the Hubble constant. A combination of ACT-DR4, WMAP, BAO, and constraints on the Hubble constant from the SH0ES collaboration gives ${\rm{\Sigma }}{m}_{\nu }={0.39}_{-0.25}^{+0.13}$ eV at 68% C.L. in extended cosmologies.

Keywords: Cosmological neutrinos, Cosmological parameters
Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics. We monitored the position of the close-by (about 370 Mpc) gamma-ray burst GRB 190829A, which originated from a massive star collapse, through very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array, carrying out a total of nine observations between 9 and 117 days after the gamma-ray burst at 5 and 15 GHz, with a typical resolution of a few milliarcseconds. From a state-of-the art analysis of these data, we obtained valuable limits on the source size and expansion rate. The limits are in agreement with the size evolution entailed by a detailed modeling of the multiwavelength light curves with a forward-plus-reverse shock model, which agrees with the observations across almost 18 orders of magnitude in frequency (including the HESS data at TeV photon energies) and more than 4 orders of magnitude in time. Thanks to the multiwavelength, high-cadence coverage of the afterglow, inherent degeneracies in the afterglow model are broken to a large extent, allowing us to capture some unique physical insights; we find a low prompt emission efficiency of ≲10-3, a low fraction of relativistic electrons in the forward shock downstream χ  e  &lt; 13% (90% credible level), and a rapid decay of the magnetic field in the reverse shock downstream after the shock crossing. While our model assumes an on-axis jet, our VLBI astrometry is not sufficiently tight as to exclude any off-axis viewing angle, but we can exclude the line of sight to have been more than ~2° away from the border of the gamma-ray-producing region based on compactness arguments.

Keywords: Gamma-ray bursts, Very long baseline interferometry, Relativistic jets, Relativistic aberration, Shocks
When Do Stars Go Boom?. The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in young star clusters in which only massive stars have had time to evolve and where the mass of the progenitor can be established from the cooling time of the WD together with the age of the cluster. Searches in young Milky Way clusters have not thus far yielded WD members more massive than about 1.1 M ⊙, well below the Chandrasekhar mass of 1.38 M ⊙, nor progenitors with masses in excess of about 6 M ⊙. However, the hunt for potentially massive WDs that escaped their cluster environs is yielding interesting candidates. To expand the cluster sample further, we used HST to survey four young and massive star clusters in the Magellanic Clouds for bright WDs that could have evolved from stars as massive as 10 M ⊙. We located five potential WD candidates in the oldest of the four clusters examined, the first extragalactic single WDs thus far discovered. As these hot WDs are very faint at optical wavelengths, final confirmation will likely have to await spectroscopy with 30 m class telescopes.

Keywords: Open star clusters, White dwarf stars, Chandrasekhar limit, Stellar evolution
On the Energization of Pickup Ions Downstream of the Heliospheric Termination Shock by Comparing 0.52-55 keV Observed Energetic Neutral Atom Spectra to Ones Inferred from Proton Hybrid Simulations. We present an unprecedented comparison of ~0.52-55 keV energetic neutral atom (ENA) heliosheath measurements, remotely sensed by the Interstellar Boundary Explorer (IBEX) mission and the Ion and Neutral Camera (INCA) on the Cassini mission, with modeled ENAs inferred from interstellar pickup protons that have been accelerated at the termination shock, using hybrid simulations, to assess the pickup ion energetics within the heliosheath. This is the first study to use hybrid simulations that are able to accurately model the acceleration of ions to tens of keV energies, which is essential in order to model ENA fluxes in the heliosheath, covering the full energy range observed by IBEX and CASSINI/INCA. The observed ENA intensities are an average value over the time period from 2009 to the end of 2012, along the Voyager 2 (V2) trajectory. The hybrid simulations upstream of the termination shock, where V2 crossed, are constrained by observations. We report an energy-dependent discrepancy between observed and simulated ENA fluxes, with the observed ENA fluxes being persistently higher than the simulated ones. Our analysis reveals that the termination shock may not accelerate pickup ions to sufficient energies to account for the observed ENA fluxes. We, thus, suggest that the further acceleration of these pickup ions is most likely occurring within the heliosheath, via additional physical processes like turbulence or magnetic reconnection. However, the redistribution of energy inside the heliosheath remains an open question.

Keywords: Heliosphere, Termination shock, Solar wind, Pickup ions, Interstellar medium, Heliosheath
Enhanced Star Formation Activity of Extreme Jellyfish Galaxies in Massive Clusters and the Role of Ram Pressure Stripping. Jellyfish galaxies are an excellent tool to investigate the short-term effects of ram pressure stripping (RPS) on star formation in cluster environments. It has been thought that the star formation activity of jellyfish galaxies may depend on the host-cluster properties, but previous studies have not yet found a clear correlation. In this study, we estimate the Hα-based star formation rates (SFRs) of five jellyfish galaxies in massive clusters (σ  v,cl ≳ 1000 km s-1) at z ~ 0.3-0.4 using Gemini GMOS/IFU observations to explore the relationship. Combining our results with those in the literature, we find that the star formation activity of jellyfish galaxies shows a positive correlation with their host-cluster velocity dispersion as a proxy of cluster mass and dynamical states. We divide the jellyfish galaxy sample into two groups with strong and weak RPS signatures using a morphological class. In the phase-space diagram, the jellyfish galaxies with strong RPS features show a higher SFR and a stronger central concentration than those with weak RPS features. We estimate their SFR excess relative to the star formation main sequence (starburstiness; R SB = SFR/SFRMS(z)) and the density of the surrounding intracluster medium (ICM) using scaling relations with the cluster velocity dispersion. As a result, the starburstiness of jellyfish galaxies with strong RPS signatures clearly exhibits positive correlations with cluster velocity dispersion, ICM density, and strength of ram pressure. This shows that the relation between RPS and star formation activity of jellyfish galaxies depends on the host-cluster properties and strength of the ram pressure.

Keywords: Galaxy clusters, Starburst galaxies, Galaxy spectroscopy, Ram pressure stripped tails, Galaxy environments, Intracluster medium
GRB 211227A as a Peculiar Long Gamma-Ray Burst from a Compact Star Merger. Long-duration gamma-ray bursts (GRBs) associated with supernovae (SNe) are believed to originate from massive star core-collapse events, whereas short-duration GRBs that are related to compact star mergers are expected to be accompanied by kilonovae. GRB 211227A, which lasted about 84 s, had an initial short/hard spike followed by a series of soft gamma-ray extended emission at redshift z = 0.228. We performed follow-up observations of the optical emission using BOOTES, LCOGT, and the Lijiang 2.4 m telescope, but we detected no associated supernova signature, even down to very stringent limits at such a low redshift. We observed the host galaxy within a large error circle and roughly estimated the physical offset of GRB 211227A as 20.47 ± 14.47 kpc from the galaxy center. These properties are similar to those of GRB 060614, and suggest that the progenitor of GRB 211227A is not favored to be associated with the death of massive stars. Hence, we propose that GRB 211227A originates from a compact star merger. Calculating pseudo-kilonova emission for this case by adopting the typical parameters, we find that any associated pseudo-kilonova is too faint to be detected. If this is the case, it explains naturally the characteristics of the prompt emission, the lack of SN and kilonova emission, and the large physical offset from the galaxy center.

Keywords: Gamma-ray bursts
Radiative Transfer Modeling of Chang'e-4 Spectroscopic Observations and Interpretation of the South Pole-Aitken Compositional Anomaly. Chang'e-4 landed in the Von Kármán basaltic zone affected by Finsen ejecta from the South Pole-Aitken (SPA) "compositional anomaly" (SPACA), providing an opportunity to untangle the origin of the SPACA. We developed a mineral abundance unmixing model and built a spectral library composed of mineral mixtures of plagioclase, low-Ca pyroxene, high-Ca pyroxene, and olivine. Based on the mineral abundances returned by our model, the average plagioclase abundance (60.4 vol.%) of SPACA is beyond the high-plagioclase end of the mineralogical range of SPA impact melt differentiation products and would require an additional contribution from crustal materials. We suggest that either the crust was not entirely removed in the SPA-forming impact or the ejecta from post-SPA basins fed feldspathic materials back onto the SPA basin floor. Our unmixing analyses indicate that the surface regolith of the SPACA is a mixture of 70.2% crustal materials and 29.8% Fe- and incompatible-element-enriched materials.

Keywords: Lunar composition, Lunar probes, The Moon, Lunar science, Lunar surface, Lunar mineralogy, Lunar evolution
The Age of Discovery with the James Webb Space Telescope: Excavating the Spectral Signatures of the First Massive Black Holes. The James Webb Space Telescope (JWST) will open a new window into the most distant universe and unveil the early growth of supermassive black holes (BHs) in the first galaxies. In preparation for deep JWST imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed BHs. We model the spectral energy distribution of super-Eddington accreting BHs with millions of solar masses in metal-poor galaxies at z ≳ 8, applying postprocess line transfer calculations to radiation hydrodynamical simulation results. Exposures of 10 ks with the NIRCam and MIRI broadband filters are sufficient to detect the radiation flux from the seed BHs with bolometric luminosities of L bol ≃ 1045 erg s-1. While the continuum colors are similar to those of typical low-z quasars, strong Hα line emission with a rest-frame equivalent width EWrest ≃ 1300 Å is so prominent that the line flux affects the broadband colors significantly. The unique colors, for instance, F356W - F560W ≳ 1 at 7 &lt; z &lt; 8 and F444W - F770W ≳ 1 at 9 &lt; z &lt; 12, provide robust criteria for photometric selection of rapidly growing seed BHs. Moreover, NIRSpec observations of low-ionization emission lines can test whether the BH is fed via a dense accretion disk at super-Eddington rates.

Keywords: Supermassive black holes, High-redshift galaxies, Quasars
Resolving the Collimation Zone of an Intermediate-mass Protostellar Jet. We report new VLA and e-MERLIN high-resolution and -sensitivity images of the triple radio continuum source in the Serpens star-forming region. These observations allowed us to perform a deep multifrequency, multiepoch study by exploring the innermost regions (≲100 au) of an intermediate-mass young stellar object for the first time, with a physical resolution of ~15 au. The kinematic analysis of knots recently ejected by the protostar indicates that the jet is undergoing episodic variations in velocity. In addition, our multifrequency images reveal striking characteristics, e.g., a highly collimated ionized stream that would be launched at a radial distance of ~0.4 au from the protostar and a narrow (~28 au wide) ionized cavity that would be excited by the interaction of a wide-angle component with the surrounding toroid of infalling material. In light of these results, we propose the scenario in which both a highly collimated jet and a wide-angle wind coexist as the most plausible to explain our observations, either launched by the X-wind or X-plus-disk-wind mechanism.

Keywords: Radio jets, Stellar winds, Interstellar medium, Radio continuum emission, Protostars
Prevalence of Thermal Nonequilibrium over an Active Region. Recent observations have shown that besides the characteristic multimillion degree component, the corona also contains a large amount of cool material called coronal rain, whose clumps are 10-100 times cooler and denser than the surroundings and are often organized in larger events, termed showers. Thermal instability (TI) within a coronal loop in a state of thermal nonequilibrium (TNE) is the leading mechanism behind the formation of coronal rain but no investigation on showers exists to date. In this study, we conduct a morphological and thermodynamic multiwavelength study of coronal rain showers observed in an active region (AR) off-limb with IRIS and the Solar Dynamics Observatory, spanning chromospheric to transition region and coronal temperatures. Rain showers were found to be widespread across the AR over the 5.45 hr observing time, with an average length, width, and duration of 27.37 ± 11.95 Mm, 2.14 ± 0.74 Mm, and 35.22 ± 20.35 minutes, respectively. We find a good correspondence between showers and the cooling coronal structures consistent with the TNE-TI scenario, thereby properly identifying coronal loops in the "coronal veil", including the strong expansion at low heights and an almost zero expansion in the corona. This agrees with previous work suggesting that the observed zero expansion in the EUV is due to specific cross-field temperature distribution. We estimate the total number of showers to be 155 ± 40, leading to a TNE volume of 4.56 ± [3.71] × 1028 cm3, i.e., on the same order of the AR volume. This suggests a prevalence of TNE over the AR indicating strongly stratified and high-frequency heating on average.

Keywords: Solar prominences, Solar coronal loops, Solar coronal heating, Solar transition region, Solar chromosphere
Quasi-periodic Accelerations of Energetic Particles during a Solar Flare. We report the observation of nonstationary quasi-periodic pulsations (QPPs) in high-energy particles during the impulsive phase of an X4.8 flare on 2002 July 23 (SOL2002-07-23T00:35). The X4.8 flare was simultaneously measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Polarimeters, and Nobeyama Radioheliograph. The quasi-period of ~50 ± 15 s, determined by the wavelet transform, is detected in the γ-ray line emission. Using the same method, a quasi-period of ~90 ± 20 s is found in the γ-ray continuum, hard X-ray (HXR), and radio emissions during almost the same time. Our observations suggest that the flare QPPs should be associated with energetic ions and nonthermal electrons that are quasi-periodically accelerated by the repetitive magnetic reconnection. The different quasi-periods between the γ-ray line and continuum/HXR/radio emissions indicate an apparent difference in acceleration or propagation between energetic ions and nonthermal electrons of this solar flare.

Keywords: Solar flares, Solar gamma-ray emission, Solar x-ray emission, Solar radio emission, Solar oscillations
Cosmological Constraints on the Global Star Formation Law of Galaxies: Insights from Baryon Acoustic Oscillation Intensity Mapping. Originally proposed as a cosmological probe of the large-scale structure, line intensity mapping (LIM) also offers a unique window into the astrophysics of galaxy evolution. Adding to the astrophysical explorations of the LIM technique that have traditionally focused on small, nonlinear scales, we present a novel method to study the global star formation law using forthcoming data from large-scale baryonic acoustic oscillation (BAO) intensity mapping. Using the amplitude of the percent-level but scale-dependent bias induced by baryon fraction fluctuations on BAO scales, we show that combining auto- and cross-correlation power spectra of two (or more) LIM signals allows to probe the star formation law power index ${ \mathcal N }$ . We examine the prospect for mapping Hα and [O III] lines across all scales, especially where imprints of the baryon fraction deviation exist, with space missions like SPHEREx. We show that although SPHEREx may only marginally probe ${ \mathcal N }$ by accessing a modest number of large-scale modes in its 200 deg2 deep survey, future infrared all-sky surveys reaching a comparable depth with an improved spectral resolution (R ≳ 400) are likely to constrain ${ \mathcal N }$ to a precision of 10%-30%, sufficient for distinguishing models with varying feedback assumptions, out to z ~ 4 using BAO intensity mapping. Leveraging this effect, large, cosmic-variance-limited LIM surveys in the far future can scrutinize the physical connection between galaxy evolution and the large-scale cosmological environment, while performing stringent tests of the standard cosmological model.

Keywords: Large-scale structure of the universe, Observational cosmology, Star formation, Galaxy evolution, Baryon acoustic oscillations