Sazuna/UAT_keywords huggingface dataset:
Atomic Gas Scaling Relations of Star-forming Galaxies at z ≈ 1. We use the Giant Metrewave Radio Telescope Cold-HI AT z ≈ 1 (CATz1) survey, a 510 hr HI 21 cm emission survey of galaxies at z = 0.74-1.45, to report the first measurements of atomic hydrogen (HI) scaling relations at z ≈ 1. We divide our sample of 11,419 blue star-forming galaxies at z ≈ 1 into three stellar-mass (M *) subsamples and obtain detections (at ≥4σ significance) of the stacked HI 21 cm emission signal from galaxies in all three subsamples. We fit a power-law relation to the measurements of the average HI mass (M HI) in the three stellar-mass subsamples to find that the slope of the M HI-M * relation at z ≈ 1 is consistent with that at z ≈ 0. However, we find that the M HI-M * relation has shifted downwards from z ≈ 1 to z ≈ 0, by a factor of 3.54 ± 0.48. Further, we find that the HI depletion timescales (t dep,HI) of galaxies in the three stellar-mass subsamples are systematically lower than those at z ≈ 0, by factors of ≈2-4. We divide the sample galaxies into three specific star formation rate (sSFR) subsamples, again obtaining ≥4σ detections of the stacked HI 21 cm emission signal in all three subsamples. We find that the relation between the ratio of HI mass to stellar mass and the sSFR evolves between z ≈ 1 and z ≈ 0. Unlike the efficiency of conversion of molecular gas to stars, which does not evolve significantly with redshift, we find that the efficiency with which HI is converted to stars is much higher for star-forming galaxies at z ≈ 1 than those at z ≈ 0.

Keywords: High-redshift galaxies, Galaxy evolution, Neutral hydrogen clouds
Interior Heating of Rocky Exoplanets from Stellar Flares with Application to TRAPPIST-1. Many stars of different spectral types with planets in the habitable zone are known to emit flares. Until now, studies that address the long-term impact of stellar flares and associated coronal mass ejections (CMEs) assumed that the planet's interior remains unaffected by interplanetary CMEs, only considering the effect of plasma/UV interactions on the atmosphere of planets. Here, we show that the magnetic flux carried by flare-associated CMEs results in planetary interior heating by ohmic dissipation and leads to a variety of interior-exterior interactions. We construct a physical model to study this effect and apply it to the TRAPPIST-1 star whose flaring activity has been constrained by Kepler observations. Our model is posed in a stochastic manner to account for uncertainty and variability in input parameters. Particularly for the innermost planets, our results suggest that the heat dissipated in the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate volcanism and outgassing of the TRAPPIST-1 planets. Furthermore, our model predicts that Joule heating can further be enhanced for planets with an intrinsic magnetic field compared to those without. The associated volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the atmosphere caused by the direct impact of flares and CMEs. To maintain consistency of atmospheric and geophysical models, the impact of stellar flares and CMEs on atmospheres of close-in exoplanetary systems needs to be studied in conjunction with the effect on planetary interiors.

Keywords: Planetary interior, Stellar flares, Exoplanet atmospheres
Revisiting the Space Weather Environment of Proxima Centauri b. Close-in planets orbiting around low-mass stars are exposed to intense energetic photon and particle radiation and harsh space weather. We have modeled such conditions for Proxima Centauri b, a rocky planet orbiting in the habitable zone of our closest neighboring star, finding a stellar wind pressure 3 orders of magnitude higher than the solar wind pressure on Earth. At that time, no Zeeman-Doppler observations of the surface magnetic field distribution of Proxima Cen were available and a proxy from a star with a similar Rossby number to Proxima was used to drive the MHD model. Recently, the first Zeeman-Doppler imaging (ZDI) observation of Proxima Cen became available. We have modeled Proxima b's space weather using this map and compared it with the results from the proxy magnetogram. We also computed models for a high-resolution synthetic magnetogram for Proxima b generated by a state-of-the-art dynamo model. The resulting space weather conditions for these three scenarios are similar with only small differences found between the models based on the ZDI observed magnetogram and the proxy. We conclude that our proxy magnetogram prescription based on the Rossby number is valid, and provides a simple way to estimate stellar magnetic flux distributions when no direct observations are available. Comparisons with models based on the synthetic magnetogram show that the exact magnetogram details are not important for predicting global space weather conditions of planets, reinforcing earlier conclusions that the large-scale (low-order) field dominates, and that the small-scale field does not have much influence on the ambient stellar wind.

Keywords: Space weather, Stellar winds, Stellar activity
Formation of Lunar Basins from Impacts of Leftover Planetesimals. The Moon holds important clues to the early evolution of the solar system. Some 50 impact basins (crater diameter D &gt; 300 km) have been recognized on the lunar surface, implying that the early impact flux was much higher than it is now. The basin-forming impactors were suspected to be asteroids released from an inner extension of the main belt (1.8-2.0 au). Here we show that most impactors were instead rocky planetesimals left behind at ~0.5-1.5 au after the terrestrial planet accretion. The number of basins expected from impacts of leftover planetesimals largely exceeds the number of known lunar basins, suggesting that the first ~200 Myr of impacts are not recorded on the lunar surface. The Imbrium basin formation (age ≃3.92 Gyr; impactor diameter d ≳ 100 km) occurs with a 15%-35% probability in our model. Imbrium must have formed unusually late to have only two smaller basins (Orientale and Schrödinger) forming afterwards. The model predicts ≃20 d &gt; 10 km impacts on the Earth 2.5-3.5 Gyr ago (Ga), which is comparable to the number of known spherule beds in the late Archean.

Keywords: Lunar impacts, Solar system formation
Neutrinos from the Brightest Gamma-Ray Burst?. We discuss implications that can be obtained by searches for neutrinos from the brightest gamma-ray burst (GRB), GRB 221009A. We derive constraints on GRB model parameters such as the cosmic-ray loading factor and dissipation radius, taking into account both neutrino spectra and effective areas. The results are strong enough to constrain proton acceleration near the photosphere, and we find that the single burst limits are comparable to those from stacking analysis. Quasi-thermal neutrinos from subphotospheres and ultra-high-energy neutrinos from external shocks are not yet constrained. We show that GeV-TeV neutrinos originating from neutron collisions are detectable, and urge dedicated analysis on these neutrinos with DeepCore and IceCube as well as ORCA and KM3NeT.

Keywords: Neutrino astronomy, Gamma-ray bursts, High energy astrophysics, Cosmic rays
What Are Those Tiny Things? A First Study of Compact Star Clusters in the SMACS0723 Field with JWST. We use the unprecedented resolution and depth of the JWST NIRCam Early Release Observations at 1-5 μm to study the stellar mass, age, and metallicity of compact star clusters in the neighborhood of the host galaxies in the SMACS J0723.3-7327 galaxy cluster field at z = 0.39. The measured colors of these star clusters show a similar distribution as quiescent galaxies at the same redshift, but are &gt;3 mag fainter than the current depths of wide-field galaxy survey. The star clusters are unresolved in the NIRCam/F150W data suggesting sizes smaller than 50 pc. This is significantly smaller than star-forming clumps or dwarf galaxies in local galaxies. From fitting their photometry with simple stellar population (SSP) models, we find stellar metallicities consistent with 0.2-0.3 Z ⊙ and ages of ${1.5}_{-0.5}^{+0.5}\,\mathrm{Gyr}$ . We rule out metallicities &lt;0.2 Z ⊙ and solar/supersolar at 4σ significance. Assuming mass-to-light ratios obtained from the best-fit SSP, we estimate stellar masses of ${2.4}_{-1.5}^{+3.0}\times {10}^{6}\,{M}_{\odot }$ . These are between average masses of local globular clusters and dwarf galaxies. Our analysis suggests middle-aged globular cluster with relatively recent formation times at z = 0.5-0.7, which could have been subsequently stripped away from their host galaxies due to interactions in the cluster environment or formed in cold flows onto the cluster core. However, we cannot rule out these objects being compact cores of stripped dwarf galaxies.

Keywords: Globular star clusters, Galaxy clusters, Galaxy formation, Stellar populations, Dwarf galaxies, Metallicity
Observational Signatures of Frame Dragging in Strong Gravity. Objects orbiting in the presence of a rotating massive body experience a gravitomagnetic frame-dragging effect, known as the Lense-Thirring effect, that has been experimentally confirmed in the weak-field limit. In the strong-field limit, near the horizon of a rotating black hole, frame dragging becomes so extreme that all objects must co-rotate with the black hole's angular momentum. In this work, we perform general relativistic numerical simulations to identify observable signatures of frame dragging in the strong-field limit that appear when infalling gas is forced to flip its direction of rotation as it is being accreted. In total intensity images, infalling streams exhibit "S"-shaped features due to the switch in the tangential velocity. In linear polarization, a flip in the handedness of spatially resolved polarization ticks as a function of radius encodes a transition in the magnetic field geometry that occurs due to magnetic flux freezing in the dragged plasma. Using a network of telescopes around the world, the Event Horizon Telescope collaboration has demonstrated that it is now possible to directly image black holes on event horizon scales. We show that the phenomena described in this work would be accessible to the next-generation Event Horizon Telescope and extensions of the array into space, which would produce spatially resolved images on event horizon scales with higher spatial resolution and dynamic range.

Keywords: Accretion, Supermassive black holes, Very long baseline interferometry, Low-luminosity active galactic nuclei, General relativity, Radiative transfer, Ergosphere, Submillimeter astronomy, Polarimetry, Magnetohydrodynamical simulations
CORINOS. I. JWST/MIRI Spectroscopy and Imaging of a Class 0 Protostar IRAS 15398–3359. The origin of complex organic molecules (COMs) in young Class 0 protostars has been one of the major questions in astrochemistry and star formation. While COMs are thought to form on icy dust grains via gas-grain chemistry, observational constraints on their formation pathways have been limited to gas-phase detection. Sensitive mid-infrared spectroscopy with JWST enables unprecedented investigation of COM formation by measuring their ice absorption features. Mid-infrared emission from disks and outflows provide complementary constraints on the protostellar systems. We present an overview of JWST/Mid-Infrared Instrument (MIRI) Medium Resolution Spectroscopy (MRS) and imaging of a young Class 0 protostar, IRAS 15398‑3359, and identify several major solid-state absorption features in the 4.9–28 μm wavelength range. These can be attributed to common ice species, such as H2O, CH3OH, NH3, and CH4, and may have contributions from more complex organic species, such as C2H5OH and CH3CHO. In addition to ice features, the MRS spectra show many weaker emission lines at 6–8 μm, which are due to warm CO gas and water vapor, possibly from a young embedded disk previously unseen. Finally, we detect emission lines from [Fe II], [Ne II], [S I], and H2, tracing a bipolar jet and outflow cavities. MIRI imaging serendipitously covers the southwestern (blueshifted) outflow lobe of IRAS 15398‑3359, showing four shell-like structures similar to the outflows traced by molecular emission at submillimeter wavelengths. This overview analysis highlights the vast potential of JWST/MIRI observations and previews scientific discoveries in the coming years.

Keywords: Stellar jets, Astrochemistry, Stellar winds, Star formation, Protostars, Complex organic molecules
The X-Ray Polarimetry View of the Accreting Pulsar Cen X-3. The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in the presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ~20 in flux. In the low-luminosity state, no significant polarization was found in either pulse phase-averaged (with a 3σ upper limit of 12%) or phase-resolved (the 3σ upper limits are 20%-30%) data. In the bright state, the polarization degree of 5.8% ± 0.3% and polarization angle of 49.°6 ± 1.°5 with a significance of about 20σ were measured from the spectropolarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anticorrelation between the flux and the polarization degree, as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49° and a magnetic obliquity of 17°. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain.

Keywords: Neutron stars, Accretion, X-ray binary stars, Polarimetry, Pulsars, Magnetic fields
Satellite Constellation Avoidance with the Rubin Observatory Legacy Survey of Space and Time. We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial satellite constellations in low-Earth orbit on the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate the orbits of currently planned Starlink and OneWeb constellations (~40,000 satellites) to test how effectively an upgraded Rubin scheduler algorithm can avoid them, and assess how the overall survey is affected. Given a reasonably accurate satellite orbit forecast, we find it is possible to adjust the scheduler algorithm to effectively avoid some satellites. Overall, sacrificing 10% of LSST observing time to avoid satellites reduces the fraction of LSST visits with streaks by a factor of 2. Whether such a mitigation will be required depends on the overall impact of streaks on science, which is not yet well quantified. This is due to a lack of adequate information about satellite brightness distributions as well as the impact of glints and low surface brightness residuals on alert purity and systematic errors in cosmological parameter estimation. A significant increase in the number of satellites or their brightness during Rubin Operations may make implementing this satellite avoidance strategy worthwhile.

Keywords: Artificial satellites, Light pollution, Sky surveys, Ground-based astronomy
Hard X-Ray Observations of the Hydrogen-poor Superluminous Supernova SN 2018hti with NuSTAR. Some hydrogen-poor superluminous supernovae are likely powered by a magnetar central engine, making their luminosity larger than common supernovae. Although a significant amount of X-ray flux is expected from the spin-down of the magnetar, direct observational evidence is still to be found, giving rise to the "missing energy" problem. Here we present NuSTAR observations of nearby SN 2018hti 2.4 yr (rest frame) after its optical peak. We expect that, by this time, the ejecta have become optically thin for photons more energetic than ~15 keV. No flux is detected at the position of the supernova down to F 10-30 keV = 9.0 × 10-14 erg cm-2 s-1, or an upper limit of 7.9 × 1041 erg s-1 at a distance of 271 Mpc. This constrains the fraction of bolometric luminosity from the putative spinning down magnetar to be f X ≲ 36% in the 10-30 keV range in a conservative case, f X ≲ 11% in an optimistic case.

Keywords: X-ray transient sources, Supernovae, Transient sources
Hidden Hearts of Neutrino Active Galaxies. Recent multimessenger studies have provided evidence for high-energy neutrino sources that are opaque to GeV-TeV gamma rays. We present model-independent studies on the connection between neutrinos and gamma rays in the active galaxy NGC 1068, and find that the neutrinos most likely come from regions within ~30-100 Schwarzschild radii. This is especially the case if neutrinos are produced via the photomeson production process, although the constraints could be alleviated if hadronuclear interactions are dominant. We consider the most favorable neutrino production regions, and discuss coronae, jets, winds, and their interactions with dense material. The results strengthen the importance of understanding dissipation mechanisms near the coronal region and the outflow base. There could be a connection between active galactic nuclei with near-Eddington accretion and tidal disruptions events, in that neutrinos are produced in the obscured vicinity of supermassive black holes.

Keywords: Gamma-ray astronomy, Neutrino astronomy, Active galactic nuclei, Particle astrophysics
If Dark Matter is Fuzzy, the First Stars Form in Massive Pancakes. Fuzzy dark matter (FDM) is a proposed modification for the standard cold dark matter (CDM) model motivated by small-scale discrepancies in low-mass galaxies. Composed of ultralight (mass ~ 1022 eV) axions with kiloparsec-scale de Broglie wavelengths, this is one of a class of candidates that predicts that the first collapsed objects form in relatively massive dark matter halos. This implies that the formation history of the first stars and galaxies would be very different, potentially placing strong constraints on such models. Here we numerically simulate the formation of the first stars in an FDM cosmology, following the collapse in a representative volume all the way down to primordial protostar formation including a primordial nonequilibrium chemical network and cooling for the first time. We find two novel results: first, the large-scale collapse results in a very thin and flat gas "pancake"; second, despite the very different cosmology, this pancake fragments until it forms protostellar objects indistinguishable from those in CDM. Combined, these results indicate that the first generation of stars in this model are also likely to be massive and, because of the sheet morphology, do not self-regulate, resulting in a massive Population III starburst. We estimate the total number of first stars forming in this extended structure to be 104 over 20 Myr using a simple model to account for the ionizing feedback from the stars, and should be observable with the James Webb Space Telescope. These predictions provide a potential smoking gun signature of FDM and similar dark matter candidates.

Keywords: Cosmology, Galaxy formation, Population III stars, Dark matter
On the Injection Scale of the Turbulence in the Partially Ionized Very Local Interstellar Medium. The cascade of magnetohydrodynamic (MHD) turbulence is subject to ion-neutral collisional damping and neutral viscous damping in the partially ionized interstellar medium. By examining the damping effects in the warm and partially ionized local interstellar medium, we find that the interstellar turbulence is damped by neutral viscosity at ~261 au and cannot account for the turbulent magnetic fluctuations detected by Voyager 1 and 2. The MHD turbulence measured by Voyager in the very local interstellar medium (VLISM) should be locally injected in the regime where ions are decoupled from neutrals for its cascade to survive the damping effects. With the imposed ion-neutral decoupling condition and the strong turbulence condition for the observed Kolmogorov magnetic energy spectrum, we find that the turbulence in the VLISM is sub-Alfvénic, and its largest possible injection scale is ~194 au.

Keywords: Magnetohydrodynamics, Heliosphere, Interstellar plasma
Numerical Modeling of Energetic Electron Acceleration, Transport, and Emission in Solar Flares: Connecting Loop-top and Footpoint Hard X-Ray Sources. The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of nonthermal electrons and suggested that, in certain flare events, electrons are primarily accelerated in the loop top and likely experience trapping and/or scattering effects. By combining the focused particle transport equation with magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic particle model that naturally incorporates electron acceleration and transport. Our simulation results indicate that physical processes such as turbulent pitch-angle scattering can have important impacts on both electron acceleration in the loop top and transport in the flare loop, and their influences are highly energy-dependent. A spatial-dependent turbulent scattering with enhancement in the loop top can enable both efficient electron acceleration to high energies and transport of abundant electrons to the footpoints. We further generate spatially resolved synthetic hard X-ray (HXR) emission images and spectra, revealing both the loop-top and footpoint HXR sources. Similar to the observations, we show that the footpoint HXR sources are brighter and harder than the loop-top HXR source. We suggest that the macroscopic particle model provides new insights into understanding the connection between the observed loop-top and footpoint nonthermal emission sources by combining the particle model with dynamically evolving MHD simulations of solar flares.

Keywords: Solar flares, Solar magnetic reconnection, Solar energetic particles, Non-thermal radiation sources, Shocks, Solar particle emission