Sazuna/UAT_keywords huggingface dataset:
Discovery of a Low-redshift Hot Dust-obscured Galaxy. We report the discovery of the hyperluminous, highly obscured active galactic nuclei (AGN) WISE J190445.04+485308.9 (W1904+4853, hereafter, L bol ~ 1.1 × 1013 L ☉) at z = 0.415. Its well-sampled spectral energy distribution (SED) is dominated by infrared dust emission, though broad emission lines are detected in the optical spectra. These features suggest that W1904+4853 contains an actively accreting supermassive black hole hidden in its dusty cocoon, resembling the observed properties of hot dust-obscured galaxies (Hot DOGs), a population previously only identified at z &gt; 1.0. Using the broad component of the Mg II 2798 Å emission line, we estimate a black hole mass of $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })=8.4\pm 0.4$ . The corresponding Eddington ratio (η) of ${1.4}_{-0.7}^{+1.3}$ implies that the central black hole accretion is at the theoretical limit of isotropic accretion. The rest-frame UV-optical SED also indicates that the host galaxy of W1904+4853 harbors strong star formation activity at the rate of 6-84 M ☉ yr-1 with an independent estimate of star formation rate up to ~45 M ☉ yr-1 using the [O II] emission line. With an estimated stellar mass of 3 × 1010 M ☉, the host galaxy appears to be a starburst system with respect to the main sequence of the star-forming galaxies at the same redshift. Although blueshifted and asymmetric [O III] emission provides evidence of an outflow, we estimate it to be an order of magnitude smaller than the star formation rate, indicating that the current obscured AGN activity at the center has not yet produced significant feedback on the host galaxy star formation activity. W1904+4853 supports the interpretation that Hot DOGs are a rare transitional phase of AGN accretion in galaxy evolution, a phase that can persist into the present-day Universe.

Keywords: Supermassive black holes, Active galaxies, Ultraluminous infrared galaxies
Cannonball or Bowling Ball: Proper Motion and Parallax for PSR J0002+6216. We report the results of careful astrometric measurements of the cannonball pulsar J0002+6216 carried out over 3 yr using the High Sensitivity Array. We significantly refine the proper motion to μ = 35.3 ± 0.6 mas yr-1 and place new constraints on the distance, with the overall effect of lowering the velocity and increasing the inferred age to 47.60 ± 0.80 kyr. Although the pulsar is brought more in line with the standard natal kick distribution, this new velocity has implications for the morphology of the pulsar wind nebula that surrounds it, the density of the interstellar medium through which it travels, and the age of the supernova remnant (CTB 1) from which it originates.

Keywords: Parallax, Pulsars, Supernova remnants, Proper motions, Interstellar medium, Pulsar wind nebulae, Astrometry
Inferring the Magnetic Field from the Rayleigh-Taylor Instability. By extending the potential approach of Layzer and Goncharov to the magnetohydrodynamics equations, we find the nonlinear solutions to the single-mode Rayleigh-Taylor instability subjected to uniform magnetic fields at various inclinations. This allows us to derive the analytical prediction of the terminal bubble and spike velocities at arbitrary Atwood numbers, which are assessed against various 2D and 3D direct numerical simulations. Contrary to the linear phase, where the magnetic field inhibits or delays the instability, the growth rate may be enhanced in the nonlinear regime, exhibiting velocities faster than the Alfvén speed. This sheds light on the importance of the nondimensional number expressing the competition between the magnetic and buoyancy effects. Conversely, we show how the orientation and the intensity of the magnetic field can be simply inferred from these solutions.

Keywords: Magnetohydrodynamics, Magnetohydrodynamical simulations
Limits on the Density of the Lunar Ionosphere: ARTEMIS Observations. The Moon of our Earth has a tenuous atmosphere, known as an exosphere. The ionization of this exosphere is speculated to possibly form a weak ionosphere. Some radio occultation (RO) experiments have suggested the presence of a dense ionosphere with an electron density on the order of hundreds of cm-3 near the surface. Using in situ measurements from the ARTEMIS mission during 2012-2021, we conduct statistical analyses and case studies to investigate the plasma density at near-surface altitudes. ARTEMIS measurements reveal no plasma densities at altitudes between 10 and 50 km that exceed 35 cm-3, and therefore they provide no evidence for a steady-state or global lunar ionosphere at the level suggested by some RO observations. Density profiles with local time and altitude show higher density in the sunlit sector than in the shadowed sector. These observations suggest that the natural variation of solar wind plasma flux with solar zenith angle plays a critical role in controlling the plasma population near the surface. This research provides a reference for a comparison with RO observations and a statistical view of the low-altitude plasma environment near the lunar surface.

Keywords: Solar wind, The Moon, Space plasmas, Lunar science
Ghostly Galaxies: Accretion-dominated Stellar Systems in Low-mass Dark Matter Halos. Wide-area deep imaging surveys have discovered large numbers of extremely low surface brightness (LSB) dwarf galaxies, which challenge galaxy formation theory and, potentially, offer new constraints on the nature of dark matter. Here we discuss one as-yet-unexplored formation mechanism that may account for a fraction of LSB dwarfs. We call this the "ghost galaxy" scenario. In this scenario, inefficient radiative cooling prevents star formation in the "main branch" of the merger tree of a low-mass dark matter halo, such that almost all its stellar mass is acquired through mergers with less massive (but nevertheless star-forming) progenitors. Present-day systems formed in this way would be "ghostly" isolated stellar halos with no central galaxy. We use merger trees based on the extended Press-Schechter formalism and the Copernicus Complexio cosmological N-body simulation to demonstrate that mass assembly histories of this kind can occur for low-mass halos in ΛCDM, but they are rare. They are most probable in isolated halos of present-day mass ~4 × 109 M ⊙, occurring for ~5% of all halos of that mass under standard assumptions about the timing and effect of cosmic reionization. The stellar masses of star-forming progenitors in these systems are highly uncertain; abundance-matching arguments imply a bimodal present-day mass function having a brighter population (median M ⋆ ~ 3 × 106 M ⊙) consistent with the tail of the observed luminosity function of ultradiffuse galaxies. This suggests that observable analogs of these systems may await discovery. We find that a stronger ionizing background (globally or locally) produces brighter and more extended ghost galaxies.

Keywords: Reionization, Dwarf galaxies, Cold dark matter
Metallicity Distribution Functions of 13 Ultra-faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging. We present uniformly measured stellar metallicities of 463 stars in 13 Milky Way (MW) ultra-faint dwarf galaxies (UFDs; M  V  = -7.1 to -0.8) using narrowband CaHK (F395N) imaging taken with the Hubble Space Telescope. This represents the largest homogeneous set of stellar metallicities in UFDs, increasing the number of metallicities in these 13 galaxies by a factor of 5 and doubling the number of metallicities in all known MW UFDs. We provide the first well-populated MDFs for all galaxies in this sample, with &lt;[Fe/H]&gt; ranging from -3.0 to -2.0 dex, and σ [Fe/H] ranging from 0.3-0.7 dex. We find a nearly constant [Fe/H]~ -2.6 over 3 decades in luminosity (~102-105 L ☉), suggesting that the mass-metallicity relationship does not hold for such faint systems. We find a larger fraction (24%) of extremely metal-poor ([Fe/H]&lt; -3) stars across our sample compared to the literature (14%), but note that uncertainties in our most metal-poor measurements make this an upper limit. We find 19% of stars in our UFD sample to be metal-rich ([Fe/H] &gt; -2), consistent with the sum of literature spectroscopic studies. MW UFDs are known to be predominantly &gt;13 Gyr old, meaning that all stars in our sample are truly ancient, unlike metal-poor stars in the MW, which have a range of possible ages. Our UFD metallicities are not well matched to known streams in the MW, providing further evidence that known MW substructures are not related to UFDs. We include a catalog of our stars to encourage community follow-up studies, including priority targets for ELT-era observations.

Keywords: Local Group, Stellar abundances, Dwarf galaxies, HST photometry
Rapid Dust Growth during Hydrodynamic Clumping due to Streaming Instability. Streaming instability is considered to be one of the dominant processes in promoting planetesimal formation by the gravitational collapse of dust clumps. The development of streaming instability is expected to form dust clumps in which the local dust density is strongly enhanced and even greater than the Roche density. The resulting clumps can collapse to form planetesimals. Recent simulations showed that such strong clumping occurs in a wider parameter space than previously expected. However, the indicated timescale for strong clumping can be on the order of tens to hundreds of Keplerian periods. In this paper, we estimate the growth time of dust grains during the pre-clumping phase. We find that the dust growth proceeds considerably before the strong clumping because even the moderate clumping due to streaming instability increases the local dust-to-gas ratio to ≳10. Depending on the sound speed, the dust collision velocity can be kept below ~1 m s-1 once sufficiently strong dust clumping occurs. Thus, even silicate grains might have the potential to grow safely toward the size whose Stokes number is unity during the clumping. Our results demonstrate the importance of local dust coagulation during dust clumping due to streaming instability.

Keywords: Protoplanetary disks, Planetesimals
Acceleration and Spectral Redistribution of Cosmic Rays in Radio-jet Shear Flows. A steady-state, semi-analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity obtained by Webb et al. is generalized to take into account more general cosmic-ray boundary spectra. This involves solving a mixed Dirichlet-Von Neumann boundary value problem at the edge of the jet. The energetic particle distribution function f 0(r, p) at cylindrical radius r from the jet axis (assumed to lie along the z-axis) is given by convolving the particle momentum spectrum ${f}_{0}(\infty ,p^{\prime} )$ with the Green's function $G(r,p;p^{\prime} )$ , which describes the monoenergetic spectrum solution in which ${f}_{0}\to \delta (p-p^{\prime} )$ as r → ∞ . Previous work by Webb et al. studied only the Green's function solution for $G(r,p;p^{\prime} )$ . In this paper, we explore for the first time, solutions for more general and realistic forms for ${f}_{0}(\infty ,p^{\prime} )$ . The flow velocity u = u(r) e  z  is along the axis of the jet (the z-axis). u is independent of z, and u(r) is a monotonic decreasing function of r. The scattering time $\tau {(r,p)={\tau }_{0}(p/{p}_{0})}^{\alpha }$ in the shear flow region 0 &lt; r &lt; r 2, and $\tau {(r,p)={\tau }_{0}(p/{p}_{0})}^{\alpha }{(r/{r}_{2})}^{s}$ , where s &gt; 0 in the region r &gt; r 2 is outside the jet. Other original aspects of the analysis are (i) the use of cosmic ray flow lines in (r, p) space to clarify the particle spatial transport and momentum changes and (ii) the determination of the probability distribution ${\psi }_{p}(r,p;p^{\prime} )$ that particles observed at (r, p) originated from r → ∞ with momentum $p^{\prime} $ . The acceleration of ultrahigh-energy cosmic rays in active galactic nuclei jet sources is discussed. Leaky box models for electron acceleration are described.

Keywords: Relativistic jets, Radio jets, Ultra-high-energy cosmic radiation, High-energy cosmic radiation
Environmental Impacts on the Rest-frame UV Size and Morphology of Star-forming Galaxies at z   2. We report the measurement of rest-frame UV size and morphology of Hα-emission-selected star-forming galaxies (HAEs) in four protoclusters at z ~ 2 (PKS 1138-262, USS 1558-003, PHz G237.0+42.5, and CC 2.2) using archival Hubble Space Telescope Advanced Camera Survey (HST/ACS) F814W data. We compare the measurement of 122 HAEs in protoclusters detected by HST/ACS to a coeval comparison field sample of 436 HAEs. We find the size distributions of protocluster and field HAEs are similar with a typical half-light radius of ~2.5 kpc. At fixed stellar mass, there is no significant difference between HAEs in the protocluster and in the field, which is also supported by stacking analyses. This result suggests that the environment does not significantly affect the size of galaxies during the star-forming phase at this epoch. Based on the Sérsic index and nonparametric morphologies, HAE morphologies in both environments at z ~ 2 in rest-frame UV are consistent with disk-like star-forming galaxies, although we also find 29% ± 4% HAEs showing disturbed morphologies. The fraction of disturbed galaxies is higher in the protocluster environment, with 39% ± 8% protocluster HAEs showing disturbed morphologies, compared to 26% ± 4% in the comparison field. The apparent disturbed morphologies are correlated with higher star formation activity and may be caused by either in situ giant clumps or mergers.

Keywords: Protoclusters, High-redshift galaxies
Magnetic Field Signatures of Intermediate-sized Impact Craters on Mars. Magnetic field signatures over impact craters provide constraints for the history of the Martian dynamo. Due to limitations of the spatial resolution of magnetic field models, previous studies primarily focused on large impact craters (mostly ≥ 500 km in diameter). To fill the impact crater age gaps of previous studies, we investigate the magnetic field signature of 23 intermediate-sized craters (150-500 km in diameter) on Mars using both MAVEN data and a magnetic field model. Ten impact craters located in the South Province, the unmagnetized primordial crust, exhibit no or weak magnetic field signatures. The other 13 impact craters produce stronger magnetic anomalies, with the ratio of the averaged magnetic field inside and outside the craters (B in/B out) ranging from 0.4 to 1.2. The B in/B out values exhibit correlation coefficients of -0.54, -0.57, and -0.69 with the diameters of craters, calculated from the MAVEN data, the crustal field model at the surface, and 150 km altitude, respectively. A B in/B out larger than 1.0 usually appears in craters with smaller diameters, which is also demonstrated by the forward modeling in this study. Furthermore, the results of the forward modeling indicate that the craters of stronger magnetizations show a larger B in/B out. According to this, the Martian dynamo can be associated with the magnetization of craters of different ages, and the characteristic time of the dynamo can be limited. Our study supports the hypothesis that the Martian dynamo weakened or ceased at ~4.0 Ga and a late dynamo was perhaps active at ~3.7 Ga.

Keywords: Impact phenomena, Mars, Magnetic fields, Planetary dynamics
Reconnection Rate and Transition from Ion-coupled to Electron-only Reconnection. Standard collisionless magnetic reconnection couples with both electron and ion dynamics. Recently, a new type of magnetic reconnection, electron-only magnetic reconnection without ion outflow, has been observed, and its reconnection rate has been found to be much higher than that in ion-coupled reconnection. In this paper, using 2D particle-in-cell simulations, we find that when the ion gyroradius is much smaller than the size of the simulation domain, magnetic reconnection is standard with ion outflows. As the ion gyroradius increases, the ion response gradually weakens, and the reconnection rate becomes higher. Electron-only reconnection occurs when the ion gyroradius is comparable to the size of the simulation domain. This trend applies to both strong and weak guide field situations. Therefore, the key factor that controls the transition from ion-coupled reconnection to electron-only reconnection is the ratio between the ion gyroradius and the size of the simulation domain. We further show that, in electron-only reconnection, when the initial electron current sheet is thinner, the reconnection rate and the electron outflow speed are higher.

Keywords: Space plasmas, Planetary magnetospheres, Plasma physics
An Asymmetric Double-degenerate Type Ia Supernova Explosion with a Surviving Companion Star. We present nebular spectroscopy of SN 2020hvf, a Type Ia supernova (SN Ia) with an early bump in its light curve. SN 2020hvf shares many spectroscopic and photometric similarities to the carbon-rich high-luminosity "03fg-like" SNe Ia. At &gt;240 days after peak brightness, we detect unambiguous emission from [Ca II] λ λ7291, 7324, which is rarely observed in normal SNe Ia and only seen in peculiar subclasses. SN 2020hvf displays "sawtooth" emission profiles near 7300 Å that cannot be explained with single symmetric velocity components of [Fe II], [Ni II], and [Ca II], indicating an asymmetric explosion. The broad [Ca II] emission is best modeled by two velocity components offset by 1220 km s-1, which could be caused by ejecta associated with each star in the progenitor system, separated by their orbital velocity. For the first time in an SN Ia, we identify narrow (FWHM = 180 ± 40 km s-1) [Ca II] emission, which we associate with a wind from a surviving, puffed-up companion star. Few published spectra have sufficient resolution and the signal-to-noise ratio necessary to detect similar narrow [Ca II] emission; however, we have detected similar line profiles in other 03fg-like SNe Ia. The extremely narrow velocity width of [Ca II] has only otherwise been observed in SNe Iax at late times. Since this event likely had a double-degenerate "super-Chandrasekhar" mass progenitor system, we suggest that a single white dwarf (WD) was fully disrupted and a wind from a surviving companion WD is producing the observed narrow emission. It is unclear whether this unique progenitor and explosion scenario can explain the diversity of 03fg-like SNe Ia, potentially indicating that multiple progenitor channels contribute to this subclass.

Keywords: Observational astronomy, White dwarf stars, Type Ia supernovae, Supernovae
A Low-mass line-rich Core Found in Massive Star-forming Region IRAS 16351-4722. We present Atacama Large Millimeter/submillimeter Array subarcsecond-resolution observations of both continuum and molecular lines at 345 GHz toward the massive star-forming region IRAS 16351-4722 (hereafter I16351). A total of 12 dust cores were detected based on high-spatial-resolution observations of the continuum. Among them, a high-mass core (11.6 M ⊙) and a low-mass core (1.7 M ⊙) show abundant molecular line emissions. 164 molecular transitions from 29 species and 104 molecular transitions from 25 species are identified in the high-mass and low-mass cores, respectively. Complex organic molecules (COMs) such as CH3OH, CH3OCHO, CH3OCH3, C2H5OH, and C2H5CN are detected in the two cores. Under the assumption of local thermodynamic equilibrium, the rotational temperatures and column densities of the COMs are derived with the XCLASS software. The maximum rotation temperature values in the low-mass core and the high-mass core were found to be approximately 130 K and 198 K, respectively. Additionally, the line widths in the high-mass core are larger than those in the low-mass one. The abundant COM line transitions, high gas temperatures, and smaller line widths indicate the presence of a low-mass line-rich core in the massive star formation region for the first time, while the high-mass line-rich core shows hot core properties. When comparing the molecular abundances of CH3OH, CH3OCHO, CH3OCH3, and C2H5OH of the two cores with other hot cores and hot corinos reported in the literature, we further confirm that both a hot core and a low-mass line-rich core are simultaneously detected in I16351.

Keywords: Spectral line identification, Star formation, Interstellar medium, Astrochemistry
Deciphering the Pre-solar-storm Features of the 2017 September Storm From Global and Local Dynamics. We investigate whether global toroid patterns and the local magnetic field topology of solar active region (AR) 12673 together can hindcast the occurrence of the biggest X-flares of solar cycle (SC)-24. Magnetic toroid patterns (narrow latitude belts warped in longitude, in which ARs are tightly bound) derived from the surface distributions of ARs, prior and during AR 12673 emergence, reveal that the portions of the south toroid containing AR 12673 was not tipped away from its north-toroid counterpart at that longitude, unlike the 2003 Halloween storms scenario. During the minimum phase there were too few emergences to determine multimode longitudinal toroid patterns. A new emergence within AR 12673 produced a complex nonpotential structure, which led to the rapid buildup of helicity and winding that triggered the biggest X-flare of SC-24, suggesting that this minimum-phase storm can be anticipated several hours before its occurrence. However, global patterns and local dynamics for a peak-phase storm, such as that from AR 11263, behaved like the 2003 Halloween storms, producing the third biggest X-flare of SC-24. AR 11263 was present at the longitude where the north and south toroids tipped away from each other. While global toroid patterns indicate that prestorm features can be forecast with a lead time of a few months, their application to observational data can be complicated by complex interactions with turbulent flows. Complex nonpotential field structure development hours before the storm are necessary for short-term prediction. We infer that minimum-phase storms cannot be forecast accurately more than a few hours ahead, while flare-prone ARs in the peak phase may be anticipated much earlier, possibly months ahead from global toroid patterns.

Keywords: Solar activity, Solar storm, Solar active regions, Solar flares
PEARLS: JWST Counterparts of Microjansky Radio Sources in the Time Domain Field. The Time Domain Field (TDF) near the North Ecliptic Pole in JWST's continuous-viewing zone will become a premier "blank field" for extragalactic science. JWST/NIRCam data in a 16 arcmin2 portion of the TDF identify 4.4 μm counterparts for 62 of 63 3 GHz sources with S(3 GHz) &gt; 5 μJy. The one unidentified radio source may be a lobe of a nearby Seyfert galaxy, or it may be an infrared-faint radio source. The bulk properties of the radio-host galaxies are consistent with those found by previous work: redshifts range from 0.14-4.4 with a median redshift of 1.33. The radio emission arises primarily from star formation in ~2/3 of the sample and from an active galactic nucleus (AGN) in ~1/3, but just over half the sample shows evidence for an AGN either in the spectral energy distribution or by radio excess. All but three counterparts are brighter than magnitude 23 AB at 4.4 μm, and the exquisite resolution of JWST identifies correct counterparts for sources for which observations with lower angular resolution would misidentify a nearby bright source as the counterpart when the correct one is faint and red. Up to 11% of counterparts might have been unidentified or misidentified absent NIRCam observations.

Keywords: AGN host galaxies, Extragalactic radio sources, Radio galaxies, High-redshift galaxies