Sazuna/UAT_keywords huggingface dataset:
Kinematics and Metallicity of the Dwarf Spheroidal Galaxy Andromeda XVIII. Andromeda XVIII is an isolated dwarf galaxy 579 kpc away from the nearest large galaxy, M31. It is a candidate "backsplash galaxy" that might have been affected by a close passage to M31. We present new Keck/DEIMOS spectroscopy of Andromeda XVIII to assess the likelihood that it is a backsplash galaxy. We estimated the velocities, metallicities ([Fe/H]), and α-enhancements ([α/Fe]) for 56 probable members. Based on the abundances of 38 stars with low errors (δ[Fe/H] &lt; 0.3), parameters for the simplest chemical evolution models were estimated using the maximum likelihood coupled with a Markov Chain Monte Carlo (MCMC) method. The metallicity distribution is inconsistent with these models, due to a sharp metal-rich cutoff. We estimated Andromeda XVIII's mean heliocentric velocity, rotation velocity, position angle of the rotation axis, and velocity dispersion using the maximum likelihood coupled with an MCMC. There is no evidence for bulk rotation, though subpopulations might be rotating. The mean heliocentric velocity is ‑337.2 km s‑1, such that the line-of-sight velocity relative to M31 is lower than the escape velocity from M31. Together, the metallicity distribution and the mean velocity are consistent with a sudden interruption of star formation. For possible causes of this quenching, we considered gas loss due to ram pressure stripping during a close passage by M31 or due to a past major merger. However, we cannot rule out internal feedback (i.e., a terminal wind).

Keywords: Local Group, Stellar abundances, Dwarf galaxies, Galaxy chemical evolution
Super-Earth Formation with Slow Migration from a Ring in an Evolving Peaked Disk Compatible with Terrestrial Planet Formation. For the origin of the radially concentrated solar system's terrestrial planets, planet formation from a ring of solids at about 1 au from the Sun with convergent/suppressed type I migration is preferred. On the other hand, many super-Earths and sub-Neptunes are found in the close-in region with orbital periods of 10–100 days, so that planet formation from rings in the 1 au region would require some degree of inward migration. One way to realize these different formation scenarios is to use different gas disk models. In this study, we investigate whether different scenarios can be realized within a single framework. We consider a disk model that evolves via disk winds and develops a density peak, and study planet formation and orbital evolution using N-body simulations. Planets with masses less than an Earth mass formed from a low-mass ring resembling the solar system do not migrate inward even in the evolving disk and remain near 1 au orbits, maintaining a high radial mass concentration. On the other hand, planets with masses greater than an Earth mass formed from a massive ring slowly migrate inward above the outward migration region. As a result, the innermost planet can move to an orbit of about 10 days. The simulation results also reproduce the characteristics (e.g., mass distribution, eccentricity, orbital separation) of the solar system and super-Earth/sub-Neptune systems. Our model predicts that Earths and sub-Earths formed by migration from rings near the 1 au region are less abundant in the close-in region.

Keywords: Planetary migration, Exoplanet formation, Solar system formation, N-body simulations
Metals in Star-forming Galaxies with KCWI. I. Methodology and First Results on the Abundances of Iron, Magnesium, and Oxygen. Understanding the chemical enrichment of different elements is crucial to gaining a complete picture of galaxy chemical evolution. In this study, we present a new sample of 46 low-redshift, low-mass star-forming galaxies at M * ∼ 108‑10 M ⊙ along with two quiescent galaxies at M * ∼ 108.8 M ⊙ observed with the Keck Cosmic Web Imager, aiming to investigate the chemical evolution of galaxies in the transition zone between Local Group satellites and massive field galaxies. We develop a novel method to simultaneously determine stellar abundances of iron and magnesium in star-forming galaxies. With the gas-phase oxygen abundance (O/H)g measured using the strong-line method, we are able to make the first-ever apples-to-apples comparison of α elements in the stars and the interstellar medium. We find that the [Mg/H]*–[O/H]g relation is much tighter than the [Fe/H]*–[O/H]g relation, which can be explained by the similar production processes of α elements. Most galaxies in our sample exhibit higher [O/H]g than [Fe/H]* and [Mg/H]*. In addition, we construct mass–metallicity relations (MZRs) measured as three different elements (Fe*, Mg*, Og). Compared to the gas O-MZR, the stellar Fe- and Mg-MZRs show larger scatter driven by variations in specific star formation rates (sSFR), with star-forming galaxies exhibiting higher sSFR and lower stellar abundances at fixed mass. The excess of [O/H]g compared to stellar abundances as well as the anticorrelation between sSFR and stellar abundance suggests that galaxy quenching of intermediate-mass galaxies at M * ∼ 108‑10 M ⊙ is primarily driven by starvation.

Keywords: Galaxy chemical evolution, Chemical abundances, Galaxy stellar content, Scaling relations, Galaxy abundances, Galaxy spectroscopy, Metallicity, Galaxies
The Nature of the High-energy γ-Ray Radiation Associated with the High-redshift Blazar B3 1343+451. High-redshift blazars are the most powerful extragalactic astrophysical sources ever detected in the high-energy γ-ray band. In this study, we present a temporal and spectral analysis of the high-redshift blazar B3 1343+451 based on 14 yr of the Fermi Large Area Telescope observations, spanning from 2008 August 4 to 2022 June 6 (MJD = 54686–59733). We extract a 7 day binned γ-ray light curve in the energy range 0.1–500 GeV and identify seven outburst periods with a peak flux of &gt;4.32 × 10‑7  ph cm‑2 s‑1. The highest 7 day flux (above 100 MeV) reaches (8.06 ± 0.56) × 10‑7  erg cm‑2 s‑1 on MJD = 56177.16, which is 10 times higher than the flux in the quiescent period. To understand the properties of distant blazar jets, we employ a standard one-zone leptonic scenario and model the multiwavelength spectral energy distributions of one quiescent and seven flaring periods. We find that the γ-ray spectrum is better reproduced when the dissipation region of the jet, R diss, is located within the molecular torus, where infrared emission is the dominant external photon field. We infer that the jets in higher-redshift blazars have larger power and kinetic energy, where the kinetic energy is significantly greater than the radiation power, and the jet production efficiency suggests that we need to lower the accretion efficiency. These results imply that B3 1343+451 may have a standard thin disk surrounding its massive black hole, and the jets of B3 1343+451 may not be fully explained by the Blandford–Payne process.

Keywords: Jets, Non-thermal radiation sources, Active galactic nuclei, Gamma-rays
Environments of Luminous Low-frequency Radio Galaxies Since Cosmic Noon: Jet-mode Feedback Dominates in Groups. Coupling between relativistic jets launched by accreting supermassive black holes and the surrounding gaseous media is a vital ingredient in galaxy evolution models. To constrain the environments in which this feedback takes place over cosmic time, we study the host-halo properties of luminous low-frequency radio galaxies (L 150 MHz ≳ 1025.25 W Hz−1) selected with the International Low-Frequency Array Telescope out to z ∼ 2 through tomographic clustering and cosmic microwave background lensing measurements. We find that these systems occupy halos characteristic of galaxy groups (M  h  = 1013─1014 h −1   M ⊙), evolving at a rate consistent with the mean growth rate of halos over the past ∼10 Gyr. The coevolution of the clustering and the luminosity function reveals that the duty cycle of these systems is of order ∼10% but has been mildly increasing since z ∼ 2, while the duty cycle of quasars has been declining. We estimate the characteristic kinetic heating power injected by powerful jets per halo as a function of mass, and compare to the same quantity injected by quasar winds. We find that powerful jet heating dominates over quasar winds in halos M  h  ≳ 1013   h −1   M ⊙ at z &lt; 2. These results conform to the paradigm of galaxy evolution in which mechanical jet power feedback is the dominant heating mechanism of the gas content of groups and clusters.

Keywords: Large-scale structure of the universe, Radio galaxies, Active galactic nuclei, Galaxy evolution, Clustering
Resolving a Candidate Dual Active Galactic Nucleus with ∼100 pc Separation in MCG-03-34-64. We report the serendipitous multiwavelength discovery of a candidate dual black hole system with a separation of ∼100 pc, in the gas-rich luminous infrared galaxy MCG-03-34-64 (z = 0.016). Hubble Space Telescope/Advanced Camera for Surveys observations show three distinct optical centroids in the [O III] narrow-band and F814W images. Subsequent analysis of Chandra/ACIS data shows two spatially resolved peaks of equal intensity in the neutral Fe Kα (6.2─6.6 keV) band, while high-resolution radio continuum observations with the Very Large Array at 8.46 GHz (3.6 cm band) show two spatially coincident radio peaks. Fast shocks as the ionizing source seem unlikely, given the energies required for the production of Fe Kα. If confirmed, the separation of ∼100 pc would represent the closest dual active galactic nuclei reported to date with spatially resolved, multiwavelength observations.

Keywords: AGN host galaxies, Seyfert galaxies, High energy astrophysics
Measurements of the Low-acceleration Gravitational Anomaly from the Normalized Velocity Profile of Gaia Wide Binary Stars and Statistical Testing of Newtonian and Milgromian Theories. Low-acceleration gravitational anomaly is investigated with a new method of exploiting the normalized velocity profile  v∼≡vp/vc  of wide binary stars as a function of the normalized sky-projected radius s/r M, where v  p  is the sky-projected relative velocity between the pair, v  c  is the Newtonian circular velocity at the sky-projected separation s, and r M is the MOND radius. With a Monte Carlo method, Gaia observed binaries and their virtual Newtonian counterparts are probabilistically distributed on the s/r M versus  v∼  plane, and a logarithmic velocity ratio parameter Γ is measured in the bins of s/r M. With three samples of binaries covering a broad range in size, data quality, and implied fraction of hierarchical systems including a new sample of 6389 binaries selected with accurate distances and radial velocities, I find a unanimous systematic variation from the Newtonian flat line. With Γ = 0 at s/r M ≲ 0.15 or s ≲ 1 kau, I get Γ = 0.068 ± 0.015 (stat)  ‑0.015+0.024  (syst) for s/r M ≳ 0.7 or s ≳ 5 kau. The gravitational anomaly (i.e., acceleration boost) factor given by γ  g  = 102Γ is measured to be  γg=1.37‑0.09+0.10  (stat)  ‑0.09+0.16  (syst). With a reduced χ 2 test of Newtonian and Milgromian nonrelativistic theories, I find that Newtonian gravity is ruled out at 5.8σ ( χν2=9.4 ) by the new sample (and 9.2σ by the largest sample used). The Milgromian AQUAL theory is acceptable with  0.7≲χν2≲3.1 . These results agree well with earlier results with the "acceleration-plane analysis" for a variety of samples and the "stacked velocity profile analysis" for a pure binary sample.

Keywords: Binary stars, Gravitation, Non-standard theories of gravity, Wide binary stars, Modified Newtonian dynamics
Improving the Automated Coronal Jet Identification with U-NET. Coronal jets are one of the most common eruptive activities in the solar atmosphere. They are related to rich physics processes, including, but not limited to, magnetic reconnection, flaring, instabilities, and plasma heating. Automated identification of off-limb coronal jets has been difficult due to their abundant nature, complex appearance, and relatively small size compared to other features in the corona. In this paper, we present an automated jet identification algorithm (AJIA) that utilizes true and fake jets previously detected by a laborious semiautomated jet detection algorithm (SAJIA) as the input of an image segmentation neural network U-NET. It is found that AJIA can achieve a much higher (0.81) detecting precision than SAJIA (0.34) while giving the possibility of whether each pixel in an input image belongs to a jet. We demonstrate that with the aid of artificial neural networks, AJIA can enable fast, accurate, and real-time off-limb coronal jet identification from Solar Dynamics Observatory/Atmospheric Imaging Assembly 304 Å observations, which are essential in studying the collective and long-term behavior of coronal jets and their relation to the solar activity cycles.

Keywords: Observational astronomy, Solar cycle, Neural networks, Plasma jets, Solar activity, Astronomy image processing
Magnetosonic Waves Excited by Maxwellian Ring Protons in Space Plasma Environment. A comprehensive theoretical model for a homogeneous plasma system of hot, tenuous Maxwellian ring-distributed protons and the cold background of Maxwellian ions and electrons is used to study the resonant instabilities of magnetosonic (MS) waves. The perpendicular velocity integrals associated with the Maxwellian ring distribution have no analytical solution, hence, are solved numerically, while the parallel velocity integrals are solved analytically by invoking series expansion of the plasma dispersion function. For the plasma parameters relevant to Earth's inner magnetosphere, the theoretical model generates MS waves with frequencies from 5 times the local proton cyclotron frequency to above the lower hybrid frequency for a propagation angle of 89.5°. Hydrogen (H+) band electromagnetic ion cyclotron waves are also excited by the Maxwellian ring protons for the same set of plasma parameters. A detailed analysis reveals that a sufficiently large ring velocity, as well as a smaller perpendicular and parallel thermal velocity, can enhance the MS wave growth. The study also explores the role of background plasma parameters in modulating the waves. The present theoretical model reproduces the harmonics of the MS waves observed by the Van Allen Probes in the Earth's inner magnetosphere. Further, the model can generate MS waves in other plasma environments, e.g., Mars, where the presence of ring protons has been established by MAVEN in connection with the MS wave observations.

Keywords: Van Allen radiation belts, Planetary magnetospheres, Space plasmas
Competitive Entrapment of Hypervolatiles in Interstellar and Cometary Water Ice Analogs. The distribution of chemical species in protoplanetary disks around young stars, especially their division between gas and solid phases, fundamentally shapes the composition of future planets and planetesimals. This distribution is likely affected by entrapment, a mechanism whereby volatile species are mechanically or chemically bound within a less volatile ice. In this study, we investigate the entrapment efficiencies of four hypervolatiles (CH4, CO, N2, and Ar) in multicomponent water ice mixtures deposited at different temperatures and mixture ratios. At low ice deposition temperatures, we observe small differences in entrapment efficiency (CH4&gt;CO&gt;N2∼Ar) up to a factor of two across species. The differences in entrapment between species increase by up to an order of magnitude with increasing deposition temperature. The relative entrapment efficiencies are also impacted by changes in the overall hypervolatile concentration of the ice mixtures. Collectively, these experiments suggest that relative entrapment efficiencies are mainly regulated by small differences in binding energies to the ice matrix, though competition for the best sites also influences entrapment in more concentrated ices. We use these results to better inform interpretations of hypervolatile observations in comets and related objects.

Keywords: Laboratory astrophysics, Chemical abundances, Astrochemistry, Planetary system formation, Protoplanetary disks, Comet volatiles , Planet formation
A Comprehensive Analysis of Insight-HXMT Gamma-Ray Burst Data. I. Power Density Spectrum. The power density spectrum (PDS) is a powerful tool to study light curves of gamma-ray bursts (GRBs). We show the average PDS and individual PDS analysis with GRB data from the Hard X-ray Modulation Telescope (also named Insight-HXMT). The values of the power-law index of the average PDS ( αP¯ ) for long GRBs (LGRBs) vary from 1.58 to 1.29 (for 100–245, 245–600, and 600–2000 keV). The Insight-HXMT data allow us to extend the energy of the LGRBs up to 2000 keV, and a relation between  αP¯  and energy E is obtained:  αP¯∝E‑0.09  (8–2000 keV). We first systematically investigate the average PDS and individual PDSs for short GRBs (SGRBs), and obtain  αP¯∝E‑0.07  (8–1000 keV), where the values of  αP¯  vary from 1.86 to 1.34. The distribution of the power-law index of an individual PDS (α) of an SGRB is consistent with that of an LGRB, and the α value for the group with a dominant timescale (the bent power law) is higher than that for the group with no dominant timescale (the single power law). Both LGRBs and SGRBs show similar α and  αP¯ , which indicates that they may be the result of similar stochastic processes. Typical values of the dominant timescale τ for LGRBs and SGRBs are 1.58 s and 0.02 s, respectively. It seems that τ varies in proportion to the duration of GRBs T 90, with a relation  τ∝T900.86 . The GRB light curve may result from superposing a number of pulses with different timescales. No periodic or quasi-periodic signal above the 3σ significance threshold is found in our sample.

Keywords: Gamma-ray bursts
Rest-frame Optical Spectroscopy of Ten z ∼ 2 Weak Emission-line Quasars. We present near-infrared spectroscopy of 10 weak emission-line quasars (WLQs) at redshifts of z ∼ 2, obtained with the Palomar 200 inch Hale Telescope. WLQs are an exceptional population of type 1 quasars that exhibit weak or no broad emission lines in the ultraviolet (e.g., the C IV λ1549 line), and they display remarkable X-ray properties. We derive Hβ-based single-epoch virial black hole masses (median value 1.7 × 109 M ⊙) and Eddington ratios (median value 0.5) for our sources. We confirm the previous finding that WLQ Hβ lines, as a major low-ionization line, are not significantly weak compared to typical quasars. The most prominent feature of the WLQ optical spectra is the universally weak/absent [O III] λ5007 emission. They also display stronger optical Fe II emission than typical quasars. Our results favor the super-Eddington accretion scenario for WLQs, where the weak lines are a result of a soft ionizing continuum; the geometrically thick inner accretion disk and/or its associated outflow is responsible for obscuring the nuclear high-energy radiation and producing the soft ionizing continuum. We also report candidate extreme [O III] outflows (blueshifts of ≍500 and 4900 km s−1) in one object.

Keywords: Accretion, High energy astrophysics, Quasars, X-ray quasars, X-ray active galactic nuclei
The Most Sensitive Radio Recombination Line Measurements Ever Made of the Galactic Warm Ionized Medium. Diffuse ionized gas pervades the disk of the Milky Way. We detect extremely faint emission from this Galactic warm ionized medium (WIM) using the Green Bank Telescope to make radio recombination line (RRL) observations toward two Milky Way sight lines: G20, (ℓ, b) = (20°, 0°), and G45, (ℓ, b) = (45°, 0°). We stack 18 consecutive Hnα transitions between 4.3 and 7.1 GHz to derive &lt;Hnα&gt; spectra that are sensitive to RRL emission from plasmas with emission measures EM ≳ 10 cm‑6 pc. Each sight line has two Gaussian-shaped spectral components with emission measures that range between ∼100 and ∼300 cm‑6 pc. Because there is no detectable RRL emission at negative LSR velocities, the emitting plasma must be located interior to the solar orbit. The G20 and G45 emission measures imply rms densities of 0.15 and 0.18 cm‑3, respectively, if these sight lines are filled with homogeneous plasma. The observed &lt;Hnβ&gt;/&lt;Hnα&gt; line ratios are consistent with LTE excitation for the strongest components. The high-velocity component of G20 has a narrow line width, 13.5 km s‑1, that sets an upper limit of ≲4000 K for the plasma electron temperature. This is inconsistent with the ansatz of a canonically pervasive, low-density, ∼10,000 K WIM plasma.

Keywords: Radio spectroscopy, Warm ionized medium, Milky Way disk, Interstellar line emission
Studying Binary Formation under Dynamical Friction Using Hill's Problem. Using the equations of motion from Hill's problem, with added accelerations for different forms of dynamical friction, we provide the (to-date) broadest scale-free study of friction-driven binary formation in gaseous disks and stellar clusters. We focus mainly on binary formation between stellar-mass black holes in active galactic nuclei (AGNs), considering both gas dynamical friction (GDF) from AGN disks and stellar dynamical friction (SDF) from the nuclear star cluster. We first find simple, dimensionless friction coefficients that approximate the effects of standard models for GDF and SDF. We perform extensive simulations of Hill's problem under such friction, and we present a picture of binary formation through encounters between single stars on nearby orbits, as a function of friction parameter, eccentricity, and inclination. Notably, we find that the local binary formation rate is a linear function of the friction coefficient so long as the friction is weak. Due to the dimensionless nature of our model problem, our findings are generalizable to binary formation at all scales (e.g., intermediate-mass black holes in a star cluster, planetesimals in a gaseous disk).

Keywords: Black holes, Orbits, Gravitational wave sources, Galaxy nuclei, Three-body problem, Dynamical friction
SN 2022oqm: A Bright and Multipeaked Calcium-rich Transient. We present the photometric and spectroscopic evolution of SN 2022oqm, a nearby multipeaked hydrogen- and helium-weak calcium-rich transient (CaRT). SN 2022oqm was detected 13.1 kpc from its host galaxy, the face-on spiral galaxy NGC 5875. Extensive spectroscopic coverage reveals an early hot (T ≥ 40,000 K) continuum and carbon features observed ∼1 day after discovery, SN Ic-like photospheric-phase spectra, and strong forbidden calcium emission starting 38 days after discovery. SN 2022oqm has a relatively high peak luminosity (M  B  = ‑17 mag) for CaRTs, making it an outlier in the population. We determine that three power sources are necessary to explain the light curve (LC), with each corresponding to a distinct peak. The first peak is powered by an expanding blackbody with a power-law luminosity, suggesting shock cooling by circumstellar material (CSM). Subsequent LC evolution is powered by a double radioactive decay model, consistent with two sources of photons diffusing through optically thick ejecta. From the LC, we derive an ejecta mass and 56Ni mass of ∼0.6 M ⊙ and ∼0.09 M ⊙. Spectroscopic modeling ∼0.6 M ⊙ of ejecta, and with well-mixed Fe-peak elements throughout. We discuss several physical origins for SN 2022oqm and find either a surprisingly massive white dwarf progenitor or a peculiar stripped envelope model could explain SN 2022oqm. A stripped envelope explosion inside a dense, hydrogen- and helium-poor CSM, akin to SNe Icn, but with a large 56Ni mass and small CSM mass could explain SN 2022oqm. Alternatively, helium detonation on an unexpectedly massive white dwarf could also explain SN 2022oqm.

Keywords: White dwarf stars, Binary stars, Supernovae