adsabs/SciX_UAT_keywords huggingface dataset:
Independent Evidence for Earlier Formation Epochs of Fossil Groups of Galaxies through the Intracluster Light: The Case for RX J100742.53+380046.6

Fossil groups (FG) of galaxies still present a puzzle to theories of structure formation. Despite the low number of bright galaxies, they have relatively high velocity dispersions and ICM temperatures often corresponding to cluster-like potential wells. Their measured concentrations are typically high, indicating early formation epochs as expected from the originally proposed scenario for their origin as being older undisturbed systems. This is, however, in contradiction with the typical lack of expected well developed cool cores. Here, we apply a cluster dynamical indicator recently discovered in the intracluster light fraction (ICLf) to a classic FG, RX J1000742.53+380046.6, to assess its dynamical state. We also refine that indicator to use as an independent age estimator. We find negative radial temperature and metal abundance gradients, the abundance achieving supersolar values at the hot core. The X-ray flux concentration is consistent with that of cool core systems. The ICLf analysis provides an independent probe of the system's dynamical state and shows that the system is very relaxed, more than all clusters, where the same analysis has been performed. The specific ICLf is about 6 times higher, than any of the clusters previously analyzed, which is consistent with an older noninteractive galaxy system that had its last merging event within the last ~5 Gyr. The specific ICLf is predicted to be an important new tool to identify fossil systems and to constrain the relative age of clusters.

Keywords: galaxy clusters; intracluster medium; cooling flows; galaxy formation
A Dynamic Trajectory Fit to Multisensor Fireball Observations

Meteorites with known orbital origins are key to our understanding of solar system formation and the source of life on Earth. Fireball networks have been developed globally in a unified effort to record and ultimately retrieve these cosmic samples. However, the accuracy of the determined orbit and the likelihood of meteorite recovery depend directly on the accuracy of the chosen meteoroid triangulation method. There are three leading techniques for meteoroid triangulation discussed in the literature: the method of planes, the straight-line least-squares method, and the multiparameter fit method. Here we describe an alternative method to meteoroid triangulation, called the dynamic trajectory fit. This approach uses the meteoroid's 3D dynamic equations of motion to fit a realistic trajectory directly to multisensor line-of-sight observations. This method has the ability to resolve fragmentation events, fit systematic observatory timing offsets, and determine mass estimates of the meteoroid along its observable trajectory. Through a comprehensive Monte Carlo analysis of over 100,000 trajectory simulations, we find this new method to more accurately estimate meteoroid trajectories of slow entry events (<25 km s-1) and events observed from low convergence angles (<10°) compared to existing meteoroid triangulation techniques. Additionally, we triangulate an observed fireball event with visible fragmentation using the various triangulation methods to show that the proposed dynamic trajectory fit implementing fragmentation to best match the captured multisensor line-of-sight data.

Keywords: meteoroids; fireballs
Giant-planet Influence on the Collective Gravity of a Primordial Scattered Disk

Axisymmetric disks of high-eccentricity, low-mass bodies on near-Keplerian orbits are unstable to an out-of-plane buckling. This "inclination instability" exponentially grows the orbital inclinations, raises perihelion distances, and clusters in the argument of perihelion. Here we examine the instability in a massive primordial scattered disk including the orbit-averaged gravitational influence of the giant planets. We show that differential apsidal precession induced by the giant planets will suppress the inclination instability unless the primordial mass is ≳20 Earth masses. We also show that the instability should produce a "perihelion gap" at semimajor axes of hundreds of astronomical units, as the orbits of the remnant population are more likely to have extremely large perihelion distances ( ${ \mathcal O }(100\,\mathrm{au})$ ) than intermediate values.

Keywords: celestial mechanics; solar system; orbits
Bright Beacons? ALMA Non-detection of a Supposedly Bright [O I] 63 μm Line in a Redshift-6 Dusty Galaxy

We report a non-detection of the [O I] 63 μm emission line from the z = 6.03 galaxy G09.83808 using ALMA Band 9 observations, refuting the previously claimed detection with APEX by Rybak et al.; the new upper limit on the [O I] 63 μm flux is almost 20-times lower. [O I] 63 μm line could be a powerful tracer of neutral gas in the Epoch of Reionization: yet our null result shows that detecting [O I] 63 μm from z ≥ 6 galaxies is more challenging than previously hypothesized.

Keywords: high-redshift galaxies; interstellar medium; submillimeter astronomy
Robust Field-level Likelihood-free Inference with Galaxies

We train graph neural networks to perform field-level likelihood-free inference using galaxy catalogs from state-of-the-art hydrodynamic simulations of the CAMELS project. Our models are rotational, translational, and permutation invariant and do not impose any cut on scale. From galaxy catalogs that only contain 3D positions and radial velocities of ~1000 galaxies in tiny ${(25\,{h}^{-1}\mathrm{Mpc})}^{3}$ volumes our models can infer the value of Ωm with approximately 12% precision. More importantly, by testing the models on galaxy catalogs from thousands of hydrodynamic simulations, each having a different efficiency of supernova and active galactic nucleus feedback, run with five different codes and subgrid models-IllustrisTNG, SIMBA, Astrid, Magneticum, SWIFT-EAGLE-we find that our models are robust to changes in astrophysics, subgrid physics, and subhalo/galaxy finder. Furthermore, we test our models on 1024 simulations that cover a vast region in parameter space-variations in five cosmological and 23 astrophysical parameters-finding that the model extrapolates really well. Our results indicate that the key to building a robust model is the use of both galaxy positions and velocities, suggesting that the network has likely learned an underlying physical relation that does not depend on galaxy formation and is valid on scales larger than ~10 h -1 kpc.

Keywords: magnetohydrodynamical simulations; astrostatistics; cosmological parameters; cosmology; hydrodynamical simulations
Mass Ejection in Failed Supernovae: Equation of State and Neutrino Loss Dependence

A failed core-collapse supernova from a nonrotating progenitor can eject mass due to a weakening of gravity associated with neutrino emission from the protoneutron star. This mechanism yields observable transients and sets an upper limit on the mass of the black hole (BH) remnant. Previous global simulations of this mechanism have included neutrino losses parametrically, however, with direct implications for the ejecta mass and energy. Here we evolve the inner supernova core with a spherically symmetric, general-relativistic neutrino radiation-hydrodynamic code until BH formation. We then use the result in a Newtonian code that follows the response of the outer layers of the star to the change in gravity and resolves the surface pressure scale height. We find that the dense-matter equation of state (EOS) can introduce a factor of ∼2 variation in gravitational mass lost to neutrinos, with a stiff EOS matching previous parametric results and a soft EOS yielding lower ejecta masses and energies by a factor of several. This difference is caused primarily by the longer time to BH formation in stiffer EOSs. With a soft EOS, our red and yellow supergiant progenitors fail to unbind mass if hydrogen recombination energy is not included. Using a linear ramp in time for mass-energy lost to neutrinos (with suitable parameters) yields a stellar response within ∼10% of that obtained using the detailed history of neutrino losses. Our results imply quantitative but not qualitative modifications to previous predictions for shock breakout, plateau emission, and final BH masses from these events.

Keywords: gravitation; hydrodynamics; supernova neutrinos; shocks; black holes; core-collapse supernovae
Constraint on the Ejecta Mass for Black Hole-Neutron Star Merger Event Candidate S190814bv

We derive the upper limit to the ejecta mass of S190814bv, a black hole-neutron star (BH-NS) merger candidate, through radiative transfer simulations for kilonovae with realistic ejecta density profiles, as well as detailed opacity and heating rate models. The limits to the ejecta mass strongly depend on the viewing angle. For the face-on observations (≤45°), the total ejecta mass should be smaller than 0.1 M⊙ for the average distance of S190814bv (D = 267 Mpc), while a larger mass is allowed for the edge-on observations. We also derive the conservative upper limits of the dynamical ejecta mass to be 0.02, 0.03, and 0.05 M⊙ for the viewing angles ≤20°, ≤50°, and ≤90°, respectively. We show that an iz-band observation deeper than 22 mag within 2 days after the gravitational-wave trigger is crucial to detect a kilonova with a total ejecta mass of 0.06 M⊙ at a distance of D = 300 Mpc. We also show that a strong constraint on the NS mass-radius relation can be obtained if future observations put an upper limit of 0.03 M⊙ on the dynamical ejecta mass for a BH-NS event with a chirp mass smaller than ≲3 M⊙ and effective spin larger than ≳0.5.

Keywords: gravitational wave astronomy; neutron stars; black holes; radiative transfer simulations
Detecting Anomalous Images in Astronomical Datasets

Environmental and instrumental conditions can cause anomalies in astronomical images, which can potentially bias all kinds of measurements if not excluded. Detection of the anomalous images is usually done by human eyes, which is slow and sometimes not accurate. This is an important issue in weak lensing studies, particularly in the era of large-scale galaxy surveys, in which image qualities are crucial for the success of galaxy shape measurements. In this work we present two automatic methods for detecting anomalous images in astronomical data sets. The anomalous features can be divided into two types: one is associated with the source images, and the other appears on the background. Our first method, called the entropy method, utilizes the randomness of the orientation distribution of the source shapes and the background gradients to quantify the likelihood of an exposure being anomalous. Our second method involves training a neural network (autoencoder) to detect anomalies. We evaluate the effectiveness of the entropy method on the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) and Dark Energy Camera Legacy Survey (DECaLS DR3) data. In CFHTLenS, with 1171 exposures, the entropy method outperforms human inspection by detecting 12 of the 13 anomalous exposures found during human inspection and uncovering 10 new ones. In DECaLS DR3, with 17112 exposures, the entropy method detects a significant number of anomalous exposures while keeping a low false-positive rate. We find that although the neural network performs relatively well in detecting source anomalies, its current performance is not as good as the entropy method.

Keywords: astronomy data analysis; sky surveys; telescopes; gravitational lensing
The VLA Frontier Field Survey: A Comparison of the Radio and UV/Optical Size of 0.3 ≲ z ≲ 3 Star-forming Galaxies

To investigate the growth history of galaxies, we measure the rest-frame radio, ultraviolet (UV), and optical sizes of 98 radio-selected, star-forming galaxies (SFGs) distributed over 0.3 ≲ z ≲ 3 with a median stellar mass of $\mathrm{log}({M}_{\star }/{M}_{\odot })\approx 10.4$ . We compare the size of galaxy stellar disks, traced by rest-frame optical emission, relative to the overall extent of star formation activity that is traced by radio continuum emission. Galaxies in our sample are identified in three Hubble Frontier Fields: MACS J0416.1-2403, MACS J0717.5+3745, and MACS J1149.5+2223. Radio continuum sizes are derived from 3 and 6 GHz radio images (≲0"6 resolution, ≈0.9 μJy beam-1 noise level) from the Karl G. Jansky Very Large Array. Rest-frame UV and optical sizes are derived using observations from the Hubble Space Telescope and the Advanced Camera for Surveys and Wide Field Camera 3 instruments. We find no clear dependence between the 3 GHz radio size and stellar mass of SFGs, which contrasts with the positive correlation between the UV/optical size and stellar mass of galaxies. Focusing on SFGs with $\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 10$ , we find that the radio/UV/optical emission tends to be more compact in galaxies with high star formation rates (≳100 M⊙ yr-1), suggesting that a central, compact starburst (and/or an active galactic nucleus) resides in the most luminous galaxies of our sample. We also find that the physical radio/UV/optical size of radio-selected SFGs with log(M⋆/M⊙) > 10 increases by a factor of 1.5-2 from z ≈ 3 to z ≈ 0.3, yet the radio emission remains two to three times more compact than that from the UV/optical. These findings indicate that these massive, radio-selected SFGs at 0.3 ≲ z ≲ 3 tend to harbor centrally enhanced star formation activity relative to their outer disks.

Keywords: galaxy structure; galaxy evolution; high-redshift galaxies; radio continuum emission
The Surface Composition of Six Newly Discovered Chemically Peculiar Stars. Comparison to the HgMn Stars mu Lep and beta Scl and the Superficially Normal B Star nu Cap

We report on a detailed abundance study of six bright, mostly southern, slowly rotating late B-stars: HD 1279 (B8III), HD 99803 (B9V), HD 123445 (B9V), HD 147550 (B9V), HD 171961 (B8III), and HD 202671 (B5II/III), hitherto reported as normal stars. We compare them to the two classical HgMn stars μ Lep and β Scl, and to the superficially normal star ν Cap. In the spectra of the six stars, the Hg II line at 3984 Å line is clearly seen and numerous lines of P, Ti, Mn, Fe, Ga, Sr, Y, and Zr appear to be strong absorbers. A comparison of newly acquired and archival spectra of these objects with a grid of synthetic spectra for selected unblended lines reveals large overabundances of P, Ti, Cr, Mn, Sr, Y, Zr, Ba, Pt, and Hg, and underabundances of He, Mg, Sc, and Ni. The effective temperatures, surface gravities, low projected rotational velocities, and the peculiar abundance patterns of the six investigated stars show that they are new chemically peculiar stars, mostly new HgMn stars, and are reclassified as such. The evolutionary status of these stars has been inferred, and their ages and masses estimated. The two most massive objects, HD 1279 and HD 202671, might have evolved away from the main sequence recently, the other stars are main-sequence objects. HD 99803A is a sharp lined HgMn star with grazing eclipses. From TESS and MASCARA photometry, we determine an orbital period of P orb = 26.12022 ± 0.00004 day.

Keywords: eclipsing binary stars; chemically peculiar stars
Exact Nonlinear Decomposition of Ideal-MHD Waves Using Eigenenergies

In this paper, we introduce a new method for exact decomposition of propagating, nonlinear magnetohydrodynamic (MHD) disturbances into their component eigenenergies associated with the familiar slow, Alfvén, and fast wave eigenmodes, and the entropy and field-divergence pseudoeigenmodes. First, the mathematical formalism is introduced, where it is illustrated how the ideal-MHD eigensystem can be used to construct a decomposition of the time variation of the total energy density into contributions from the eigenmodes. The decomposition method is then demonstrated by applying it to the output of three separate nonlinear MHD simulations. The analysis of the simulations confirms that the component wave modes of a composite wavefield are uniquely identified by the method. The slow, Alfvén, and fast energy densities are shown to evolve in exactly the way expected from comparison with known linear solutions and nonlinear properties, including processes such as mode conversion. Along the way, some potential pitfalls for the numerical implementation of the decomposition method are identified and discussed. We conclude that the exact, nonlinear decomposition method introduced is a powerful and promising tool for understanding the nature of the decomposition of MHD waves as well as analyzing and interpreting the output of dynamic MHD simulations.

Keywords: magnetohydrodynamics; magnetohydrodynamical simulations; solar physics; alfven waves
JWST/NIRCam Transmission Spectroscopy of the Nearby Sub-Earth GJ 341b

We present a JWST/Near Infrared Camera (NIRCam) transmission spectrum from 3.9 to 5.0 μm of the recently validated sub-Earth GJ 341b (R P = 0.92 R ⊕, T eq = 540 K) orbiting a nearby bright M1 star (d = 10.4 pc, K mag = 5.6). We use three independent pipelines to reduce the data from the three JWST visits and perform several tests to check for the significance of an atmosphere. Overall, our analysis does not uncover evidence of an atmosphere. Our null hypothesis tests find that none of our pipelines' transmission spectra can rule out a flat line, although there is weak evidence for a Gaussian feature in two spectra from different pipelines (at 2.3 and 2.9σ). However, the candidate features are seen at different wavelengths (4.3 μm versus 4.7 μm), and our retrieval analysis finds that different gas species can explain these features in the two reductions (CO2 at 3.1σ compared to O3 at 2.9σ), suggesting that they are not real astrophysical signals. Our forward-model analysis rules out a low-mean-molecular-weight atmosphere (<350× solar metallicity) to at least 3σ, and disfavors CH4-dominated atmospheres at 1–3σ, depending on the reduction. Instead, the forward models find our transmission spectra are consistent with no atmosphere, a hazy atmosphere, or an atmosphere containing a species that does not have prominent molecular bands across the NIRCam/F444W bandpass, such as a water-dominated atmosphere. Our results demonstrate the unequivocal need for two or more transit observations analyzed with multiple reduction pipelines, alongside rigorous statistical tests, to determine the robustness of molecular detections for small exoplanet atmospheres.

Keywords: extrasolar rocky planets; exoplanets
A Multiwavelength Study of PSR J1119-6127 after 2016 Outburst

The high magnetic field pulsar PSR J1119-6127, detected from radio to high-energy wavelengths, underwent a magnetar-like outburst beginning on 2016 July 27. In this paper, we study the postoutburst multiwavelength properties of this pulsar from the radio to GeV bands and discuss its similarity with the outburst of the magnetar XTE J1810-197. In phase-resolved spectral analysis of 0.5-10 keV X-ray data collected in 2016 August, the on- and off-pulse spectra are both characterized by two blackbody components and also require a power-law component similar to the hard X-ray spectra of magnetars. This power-law component is no longer distinguishable in data from 2016 December. We likewise find that there was no substantial shift between the radio and X-ray pulse peaks after the 2016 X-ray outburst. The gamma-ray pulsation after the X-ray outburst is confirmed with data taken after 2016 December, and the pulse structure and phase difference between the gamma-ray and radio peaks (∼0.4 cycle) are also consistent with those before the X-ray outburst. These multiwavelength observations suggest that the reconfiguration of the global magnetosphere after the 2016 magnetar-like outburst continued for at most about 6 months. We discuss the evolution of the X-ray emission after the 2016 outburst with the untwisting magnetosphere model.

Keywords: penumbra; periodic variable stars; photographic astrometry; polar caps; proton-proton reaction; x-ray bright point; x-ray point sources; plasma astrophysics; phase error; phase effect; model selection; neutron stars
Determination of Rotation Periods for a Large Sample of Asteroids from the K2 Campaign 9

The Kepler mission is a powerful tool for the study of different types of astrophysical objects or events in the distant universe. However, the spacecraft also provides an opportunity to study solar system objects passing in the telescope's field of view. The aim of this paper is to determine, for the first time, the rotation periods of a number of asteroids observed by the K2 satellite during the K2 Campaign 9. Using publicly available data from the Kepler mission, we have used the Modified Causal Pixel Model code to perform the aperture-like and point-response function-like photometry of 1026 asteroids. The results allowed us to determine the rotation periods for 188 asteroids. For asteroids with rotation periods that were previously measured, we compared the results and found very good agreement. There are an additional 20 asteroids for which we obtained lower limits on rotation periods and in all cases these limits are at least 100 hr.

Keywords: small solar system bodies; asteroids
Molecules with ALMA at Planet-forming Scales (MAPS). XV. Tracing Protoplanetary Disk Structure within 20 au

Constraining the distribution of gas and dust in the inner 20 au of protoplanetary disks is difficult. At the same time, this region is thought to be responsible for most planet formation, especially around the water ice line at 3-10 au. Under the assumption that the gas is in a Keplerian disk, we use the exquisite sensitivity of the Molecules with ALMA at Planet-forming Scales (MAPS) ALMA large program to construct radial surface brightness profiles with a ~3 au effective resolution for the CO isotopologue J = 2-1 lines using the line velocity profile. IM Lup reveals a central depression in 13CO and C18O that is ascribed to a pileup of ~500 M⊕ of dust in the inner 20 au, leading to a gas-to-dust ratio of around <10. This pileup is consistent with an efficient drift of grains (≳100 M⊕ Myr-1) and a local gas-to-dust ratio that suggests that the streaming instability could be active. The CO isotopologue emission in the GM Aur disk is consistent with a small (~15 au), strongly depleted gas cavity within the ~40 au dust cavity. The radial surface brightness profiles for both the AS 209 and HD 163296 disks show a local minimum and maximum in the C18O emission at the location of a known dust ring (~14 au) and gap (~10 au), respectively. This indicates that the dust ring has a low gas-to-dust ratio (>10) and that the dust gap is gas-rich enough to have optically thick C18O. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

Keywords: millimeter astronomy; protoplanetary disks; planet formation