adsabs/SciX_UAT_keywords huggingface dataset:
Confirmation of an Anomalously Low Dark Matter Content for the Galaxy NGC 1052-DF4 from Deep, High-resolution Continuum Spectroscopy

NGC 1052-DF4 was found to be the second "galaxy lacking dark matter" in the NGC 1052 group, based on its velocity dispersion of ${\sigma }_{\mathrm{gc}}={4.2}_{-2.2}^{+4.4}$ km s-1 as measured from the radial velocities of seven of its globular clusters. Here we verify this result by measuring the stellar velocity dispersion of the galaxy. We observed the diffuse stellar light in NGC 1052-DF4 with the Keck Cosmic Web Imager in its highest-resolution mode, with ${\sigma }_{\mathrm{instr}}\approx 7$ km s-1. With a total science + sky exposure time of 34 hr, the resulting spectrum is exceptional in both its spectral resolution and its signal-to-noise ratio of 23 Å-1. We find a stellar velocity dispersion of ${\sigma }_{\mathrm{stars}}={8.0}_{-1.9}^{+2.3}$ km s-1, consistent with the previous measurement from the globular clusters. Combining both measurements gives a fiducial dispersion of ${\sigma }_{{\rm{f}}}={6.3}_{-1.6}^{+2.5}$ km s-1. The implied dynamical mass within the half-light radius is ${8}_{-4}^{+6}\times {10}^{7}{M}_{\odot }$ . The expected velocity dispersion of NGC 1052-DF4 from the stellar mass alone is 7 ± 1 km s-1, and for a Navarro-Frenk-White (NFW) halo that follows the stellar mass-halo mass relation and the halo mass-concentration relation, the expectation is ~30 km s-1. The low velocity dispersion rules out a normal NFW dark matter halo, and we confirm that NGC 1052-DF4 is one of at least two galaxies in the NGC 1052 group that have an anomalously low dark matter content. While any viable model for their formation should explain the properties of both galaxies, we note that NGC 1052-DF4 now poses the largest challenge, as it has the most stringent constraints on its dynamical mass.

Keywords: high resolution spectroscopy; galaxy kinematics; stellar kinematics
Microwave and Hard X-Ray Flare Observations by NoRH/NoRP and RHESSI: Peak-flux Correlations

This paper presents initial results from a statistical study of solar microwave and hard X-ray flares jointly observed over the past two solar cycles by the Nobeyama Radio Polarimeters, the Nobeyama Radio Heliograph, and the Reuven Ramaty High Energy Solar Spectroscopic Imager. As has been previously demonstrated, the microwave (17 GHz and 34 GHz) peak flux shows a linear correlation with the nonthermal hard X-ray bremsstrahlung peak emission seen above 50 keV. The correlation holds for the entire rise phase of each individual burst, while the decay phases tend to show more extended emission at microwaves than is generally attributed to particle trapping. While the correlation is highly significant (coefficient of 0.92) and holds over more than four orders of magnitude, individual flares can be above or below the fitted line by an average factor of about 2. By restricting the flare selection to source morphologies with the radio emission from the top of the flare loop, the correlation tightens significantly, with a correlation coefficient increasing to 0.99 and the scatter reduced to a factor of 1.3. These findings corroborate the assumption that gyrosynchrotron microwave and hard X-ray bremsstrahlung emissions are produced by the same flare-accelerated electron population. The extent of the linear correlation over four orders of magnitude suggests that magnetic field strengths within nonthermal 17 GHz sources are surprisingly similar over a wide range of flare sizes.

Keywords: solar x-ray flares
Multiline Assessment of Narrow-line Regions in z 3 Radio Galaxies

In this paper, we use high-quality rest-UV spectra of three radio galaxies at z ~ 3 observed with the FORS2 camera on the Very Large Telescope to measure the flux of several emission lines, including relatively faint ones, such as N IV]λ1486, O III]λ1663, and [Ne IV]λ2424. Additionally, we collect fluxes of faint rest-UV emission lines in 12 z ~ 3 radio galaxies from the literature. Previously, physical and chemical properties of narrow-line regions (NLRs) in high-z active galactic nuclei (AGNs) have been investigated mostly by using only strong rest-UV emission lines (e.g., N V λ1240, C IV λ1549, He II λ1640, and C III]λ1909). Such strong-line diagnostics are based on various assumptions due to the limitation in the number of available emission-line constraints. In this work, both physical and chemical properties of NLR clouds in each object are estimated by fitting detailed photoionization models to the measured emission-line fluxes. We confirm that the metallicity of NLRs in AGNs at z ~ 3 is solar or supersolar, without assumptions about the gas density and ionization parameter thanks to the constraints from the faint emission lines. This result suggests that high-z radio galaxies are already chemically mature at z ~ 3.

Keywords: active galaxies; interstellar medium; active galactic nuclei
The Archival Discovery of a Strong Lyα and [C II] Emitter at z = 7.677

We report the archival discovery of Lyα emission from the bright ultraviolet galaxy Y002 at z = 7.677, spectroscopically confirmed by its ionized carbon [C II] 158 μm emission line. The Lyα line is spatially associated with the rest-frame UV stellar emission (M UV ~ -22, 2× brighter than ${M}_{\mathrm{UV}}^{\star }$ ), and it appears offset from the peak of the extended [C II] emission at the current ~1″ spatial resolution. We derive an estimate of the unobscured SFRUV = (22 ± 1) M ⊙ yr-1 and set an upper limit of SFRIR < 15 M ⊙ yr-1 from the far-infrared (FIR) wavelength range, which globally places Y002 on the SFR(UV+IR)-L [C II] correlation observed at lower redshifts. In terms of velocity, the peak of the Lyα emission is redshifted by Δv Lyα ~ 500 km s-1 from the systemic redshift set by [C II] and a high-velocity tail extends up to ~1000 km s-1. The velocity offset is up to ~3.5× higher than the average estimate for similarly UV-bright emitters at z ~ 6-7, which might suggest that we are witnessing the merging of two clumps. A combination of strong outflows and the possible presence of an extended ionized bubble surrounding Y002 would likely facilitate the escape of copious Lyα light, as indicated by the large equivalent width EW0(Lyα) $\,=\,{24}_{-6}^{+5}$ Å. Assuming that [C II] traces the neutral hydrogen, we estimate a H I gas fraction of M H I/M ⋆ ≳ 8 for Y002 as a system and speculate that patches of high H I column densities could contribute to explaining the observed spatial offsets between Lyα- and [C II]-emitting regions. The low dust content, implied by the nondetection of the FIR continuum emission at rest frame ~160 μm, would be sufficient to absorb any potential Lyα photons produced within the [C II] clump as a result of large H I column densities.

Keywords: lyman-alpha galaxies; lyman-break galaxies; high-redshift galaxies; reionization; galaxy evolution; interstellar medium
Planetesimal Growth in Evolving Protoplanetary Disks: Constraints from the Pebble Supply

In the core accretion model, planetesimals grow by mutual collisions and engulfing millimeter-to-centimeter particles, i.e., pebbles. Pebble accretion can significantly increase the accretion efficiency and help explain the presence of planets on wide orbits. However, the pebble supply is typically parameterized as a coherent pebble mass flux, sometimes being constant in space and time. Here we solve the dust advection and diffusion within viciously evolving protoplanetary disks to determine the pebble supply self-consistently. The pebbles are then accreted by planetesimals interacting with the gas disk via gas drag and gravitational torque. The pebble supply is variable with space and decays with time quickly, with a pebble flux below 10 M ⊕ Myr-1 after 1 Myr in our models. As a result, only when massive planetesimals (>0.01 M ⊕) are luckily produced by the streaming instability or the disk has low viscosity (α ~ 0.0001) can the herd of planetesimals grow over a Mars mass within 2 Myr. By then, planetesimals only capture pebbles about 50 times their mass and as little as 10 times beyond 20 au due to limited pebble supply. Further studies considering multiple dust species in various disk conditions are warranted to fully assess the realistic pebble supply and its influence on planetesimal growth.

Keywords: planetesimals; protoplanetary disks; circumstellar dust; planet formation
The Impact of Baryonic Physics on the Abundance, Clustering, and Concentration of Halos

We examine the impact of baryonic physics on the halo distribution in hydrodynamic simulations compared to that in dark matter-only (DMO) simulations. We find that, in general, DMO simulations produce halo mass functions (HMFs) that are shifted to higher halo masses than their hydrodynamic counterparts due to the lack of baryonic physics. However, the exact nature of this mass shift is a complex function of mass, halo definition, redshift, and larger-scale environment, and it depends on the specifics of the baryonic physics implemented in the simulation. We present fitting formulae for the corrections one would need to apply to each DMO halo catalog in order to reproduce the HMF found in its hydrodynamic counterpart. Additionally, we explore the dependence on environment of this HMF discrepancy and find that, in most cases, halos in low-density environments are slightly more impacted by baryonic physics than halos in high-density environments. We thus also provide environment-dependent mass correction formulae that can reproduce the conditional, as well as global, HMF. We show that our mass corrections also repair the large-scale clustering of halos, though the environment-dependent corrections are required to achieve an accuracy better than 2%. Finally, we examine the impact of baryonic physics on the halo mass-concentration relation and find that its slope in hydrodynamic simulations is consistent with that in DMO simulations. Ultimately, we recommend that any future work relying on DMO halo catalogs incorporate our mass corrections to test the robustness of their results to baryonic effects.

Keywords: galaxy dark matter halos; hydrodynamical simulations; n-body simulations
The Full Extent of the Tidal Tail in Arp 93

Arp 93 consists of two interacting galaxies, NGC 7284 and NGC 7284 and a long tidal tail. However, it has not been depicted in its fullest extent in previous images. I present a deep, new image that illustrates the tail's wide path, that is more than double the previously recorded angular distance from the interacting pair of galaxies.

Keywords: tidal tails; interacting galaxies
Chemical Abundances of Young Massive Clusters in NGC 1313

We analyze spectroscopic observations of five young massive clusters (YMCs) in the barred spiral galaxy NGC 1313 to obtain detailed abundances from their integrated light. Our sample of YMCs was observed with the X-shooter spectrograph on the Very Large Telescope. We make use of theoretical isochrones to generate synthetic integrated-light spectra, iterating on the individual elemental abundances until converging on the best fit to the observations. We measure abundance ratios for [Ca/Fe], [Ti/Fe], [Mg/Fe], [Cr/Fe], and [Ni/Fe]. We estimate an Fe abundance gradient of -0.124 ± 0.034 dex kpc-1, and a slightly shallower α gradient of -0.093 ± 0.009 dex kpc-1. This is in contrast to previous metallicity studies that focused on the gas-phase abundances, which have found NGC 1313 to be the highest-mass barred galaxy known not to have a radial abundance gradient. We propose that the gradient discrepancy between the different studies originates from the metallicity calibrations used to study the gas-phase abundances. We also observe an age-metallicity trend that supports a scenario of constant star formation throughout the galaxy, with a possible burst in star formation in the southwest region where YMC NGC 1313-379 is located. ∗ Based on observations made with ESO telescopes at the La Silla Paranal Observatory under program ID 084.B-0468(A).

Keywords: chemical abundances; stellar abundances; extragalactic astronomy; young star clusters; star clusters
Far-UV and Optical Emissions from Three Very Large Supernova Remnants Located at Unusually High Galactic Latitudes

Galactic supernova remnants (SNRs) with angular dimensions greater than a few degrees are relatively rare, as are remnants located more than 10° off the Galactic plane. Here we report a UV and optical investigation of two previously suspected SNRs more than 10° in both angular diameter and Galactic latitude. One is a proposed remnant discovered in 2008 through 1420 MHz polarization maps near Galactic coordinates l = 353°, b = -34°. GALEX far-UV (FUV) and Hα emission mosaics show the object's radio emission coincident with an 11° × 14° shell of UV filaments that surrounds a diffuse Hα emission ring. Another proposed high-latitude SNR is the 20° × 26° Antlia nebula (G275.5+18.4) discovered in 2002 through low-resolution all-sky Hα and ROSAT soft X-ray emissions. GALEX FUV and Hα mosaics along with optical spectra indicate the presence of shocks throughout the Antlia nebula with estimated shock velocities of 70 to over 100 km s-1. We also present evidence that it has collided with the NE rim of the Gum Nebula. We find both of these large nebulae are bona fide SNRs with ages less than 105 yr despite their unusually large angular dimensions. We also present FUV and optical images along with optical spectra of a new high-latitude SNR (G249.7+24.7) some 4.5° in diameter which has also been independently discovered in X-rays and radio (Becker at al. 2021). We find this remnant's distance to be ≤400 pc based on the detection of red and blue Na I absorption features in the spectra of two background stars.

Keywords: supernova remnants
The Behavior of HgMn Stars in the Far UV-Paper 18: HD 209459

The analysis of 14 high resolution spectra of the Hg star HD 209459 recorded by the SWP camera on board the International Ultraviolet Explorer reveals large variations of the far ultraviolet flux of this star over the 18 yr of the mission. The two available Transiting Exoplanet Survey Satellite lightcurves of HD 209459 are periodic. The period, measured between two successive minima, is close to 6.25 ± 0.03 days which could be the rotational period of HD 209459. The FUV variations, which are unexpected for a late normal B-type star or a Hg-rich star, could be caused by large horizontal chemical or occasional thermal gradients.

Keywords: chemically peculiar stars; mercury-manganese stars
Detecting the Early Optical Flashes of Gamma-Ray Bursts with Small Telescope Arrays

We present an observational approach for the independent detection of the early optical emission of long gamma-ray bursts (GRBs). For this purpose, we explore the potential of the Large Array Survey Telescope (LAST). This array of small optical telescopes can be used to scan a wide region of the sky, and to focus on a smaller field of view with increased sensitivity, as needed. The modularity of the array facilitates dynamic scanning of multiple fields, by shifting telescope pointing directions with high cadence. This can significantly increase the effective sky-coverage of a blind survey on short timescales. For events associated with gamma-ray counterparts, the valuable early time data can supplement high-energy observations. Regardless of gamma-ray association, detections can potentially be used to explore various phenomena associated with GRBs, such as orphan afterglows; dirty fireballs; and choked jets. We simulate a sample of GRBs and their respective optical signals at early times. After accounting for dynamic cadence, the light curves are given as input to a machine-learning classifier, used to identify astrophysical transients. We find that, by dedicating half of an LAST array to a blind search, one would expect to independently detect 7–11 GRBs yr–1, corresponding to an approximate intrinsic event rate of 0.12 deg–2 yr–1.

Keywords: gamma-ray bursts; optical astronomy; transient detection
Panning for Gold: New Emission Lines from UV-VIS Spectroscopy of Au I and Au II

The recent detection of a neutron star merger by the LIGO collaboration has renewed interest in laboratory studies of r-process elements. Accurate modeling and interpretation of the electromagnetic transients following the mergers requires computationally expensive calculations of both the structure and opacity of all trans-iron elements. To date, the necessary atomic data to benchmark structure codes are incomplete or, in some cases, absent entirely. Within the available laboratory studies, the literature on Au I and Au II provides incomplete reports of the emission lines and level structures. We present a new study of Au I and Au II lines and levels by exposing a solid gold target to plasma in the Compact Toroidal Hybrid (CTH) experiment at Auburn University. A wavelength range from 187 to 800 nm was studied. In Au I, 86 lines are observed, 43 of which are unreported in the literature, and the energies of 18 $5{d}^{9}6s6p$ levels and 16 of the 18 known $5{d}^{9}6s6d$ levels are corroborated by a least-squares level energy optimization. In Au II, 76 emission lines are observed, and 51 of the lines are unreported in the literature. For both Au I and Au II, the new lines predominantly originate from the most energetic of the known levels, and over half of the new Au II lines have wavelengths longer than 300 nm. For the estimated electron parameters of CTH plasmas at the gold target (ne ∼ 1012 cm-3, Te ∼ 10 eV), two-electron transitions are similar in intensity to LS-allowed one-electron transitions.

Keywords: atomic spectroscopy; laboratory astrophysics; spectral line lists; spectral line identification; r-process; chemically peculiar stars
Pluto's Surface Mapping Using Unsupervised Learning from Near-infrared Observations of LEISA/Ralph

We map the surface of Pluto using an unsupervised machine-learning technique using the near-infrared observations of the LEISA/Ralph instrument on board NASA's New Horizons spacecraft. The principal-component-reduced Gaussian mixture model was implemented to investigate the geographic distribution of the surface units across the dwarf planet. We also present the likelihood of each surface unit at the image pixel level. Average I/F spectra of each unit were analyzed-in terms of the position and strengths of absorption bands of abundant volatiles such as N2, CH4, and CO and nonvolatile H2O-to connect the unit to surface composition, geology, and geographic location. The distribution of surface units shows a latitudinal pattern with distinct surface compositions of volatiles-consistent with the existing literature. However, previous mapping efforts were based primarily on compositional analysis using spectral indices (indicators) or implementation of complex radiative transfer models, which need (prior) expert knowledge, label data, or optical constants of representative end-members. We prove that an application of unsupervised learning in this instance renders a satisfactory result in mapping the spatial distribution of ice compositions without any prior information or label data. Thus, such an application is specifically advantageous for a planetary surface mapping when label data are poorly constrained or completely unknown, because an understanding of surface material distribution is vital for volatile transport modeling at the planetary scale. We emphasize that the unsupervised learning used in this study has wide applicability and can be expanded to other planetary bodies of the solar system for mapping surface material distribution.

Keywords: pluto; surface ices; astronomy data analysis; astrostatistics techniques; astroinformatics
Determination of Lens Mass Density Profile from Strongly Lensed Gravitational-wave Signals

As the interferometers detecting gravitational waves are upgraded, improving their sensitivity, the probability of observing strong lensing increases. Once a detection is made, it will be critical to gain as much information as possible about the lensing object from these observations. In this work, we present a methodology to rapidly perform model selection between differing mass density profiles for strongly lensed gravitational-wave signals, using the results of the fast strong-lensing analysis pipeline GOLUM. We demonstrate the validity of this methodology using some illustrative examples adopting the idealized singular isothermal sphere and point-mass lens models. We take several simulated lensed signals, analyze them with GOLUM, and subject them to our methodology to recover both the model and its parameters. To demonstrate the methodology's stability, we show how the result varies with the number of samples used for a subset of these injections. In addition to the analysis of simulations, we also apply our methodology to the gravitational-wave event pair GW191230-LGW200104, two events with similar frequency evolutions and sky locations, which was analyzed in detail as a potential lensing candidate but ultimately discarded when considering the full population and the uncertain nature of the second event. We find a preference for the singular isothermal sphere model over the point mass, though our posteriors are much wider than for the lensed injections, in line with the expectations for a nonlensed event. The methodology developed in this work is made available as part of the GRAVELAMPS software package.

Keywords: gravitational lensing; gravitational waves; strong gravitational lensing
GRB 200829A: External-shock Origin of the Very Early Prompt Emission?

Long-duration GRB 200829A was detected by Fermi-GBM and Swift-BAT/XRT, and then rapidly observed by other ground-based telescopes. It has a weak γ-ray emission in the very early phase and is followed by a bright spiky γ-ray emission pulse. The radiation spectrum of the very early emission is best fitted by a power-law function with index ~-1.7. However, the bright spiky γ-ray pulse, especially the time around the peak, exhibits a distinct two-component radiation spectrum, i.e., Band function combined with a blackbody radiation spectrum. We infer the photospheric properties and reveal a medium magnetization at a photospheric position by adopting the initial size of the outflow as r 0 = 109 cm. It implies that the Band component in this pulse may be formed during the dissipation of the magnetic field. The power-law radiation spectra found in the very early prompt emission may imply the external-shock origination of this phase. Then, we perform the Markov Chain Monte Carlo method fitting on the light curves of this burst, where the jet corresponding to the γ-ray pulse at around 20 s is used to refresh the external shock. It is shown that the light curves of the very early phase and X-ray afterglow after 40 s, involving the X-ray bump at around 100 s, can be well modeled in the external-shock scenario. For the obtained initial outflow, we estimate the minimum magnetization factor of the jet based on the fact that the photospheric emission of this jet is missed in the very early phase.

Keywords: gamma-ray bursts