adsabs/SciX_UAT_keywords huggingface dataset:
The Ionized Warped Disk and Disk Wind of the Massive Protostar Monoceros R2-IRS2 Seen with ALMA

Theories of massive star formation predict that massive protostars accrete gas through circumstellar disks. Although several cases have been found already thanks to high angular-resolution interferometry, the internal physical structure of these disks remains unknown, in particular whether they present warps or internal holes, as observed in low-mass protoplanetary disks. Here, we report very high angular-resolution observations of the H21α radio recombination line carried out in Band 9 with the Atacama Large Millimeter/submillimeter Array (beam of 80 mas × 60 mas, or 70 au × 50 au) toward the IRS2 massive young stellar object in the Monoceros R2 star-forming cluster. The H21α line shows maser amplification, which allows us to study the kinematics and physical structure of the ionized gas around the massive protostar down to spatial scales of ∼1-2 au. Our ALMA images and 3D radiative transfer modeling reveal that the ionized gas around IRS2 is distributed in a Keplerian circumstellar disk and an expanding wind. The H21α emission centroids at velocities between -10 and 20 km s-1 deviate from the disk plane, suggesting a warping for the disk. This could be explained by the presence of a secondary object (a stellar companion or a massive planet) within the system. The ionized wind seems to be launched from the disk surface at distances ∼11 au from the central star, consistent with magnetically-regulated disk wind models. This suggests a similar wind-launching mechanism to that recently found for evolved massive stars such as MWC349A and MWC922.

Keywords: star formation
EPOCHS. II. The Ultraviolet Luminosity Function from 7.5 < z < 13.5 Using 180 arcmin2 of Deep, Blank Fields from the PEARLS Survey and Public JWST Data

We present an analysis of the ultraviolet luminosity function (UV LF) and star formation rate density of distant galaxies (7.5 < z < 13.5) in the "blank" fields of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) survey combined with Early Release Science data from the CEERS, GLASS, and NGDEEP surveys/fields and the first data release of JADES. We use strict quality cuts on EAZY photometric redshifts to obtain a reliable selection and characterization of high-redshift (z > 6.5) galaxies from a consistently processed set of deep, near-infrared imaging. Within an area of 180 arcmin2, we identify 1046 candidate galaxies at redshifts z > 6.5 and we use this sample to study the UV LF in four redshift bins between 7.5 < z < 13.5. The measured number density of galaxies at z = 8 and z = 9 matches those of past observations undertaken by the Hubble Space Telescope (HST). Our z = 10.5 measurements lie between early James Webb Space Telescope (JWST) results and past HST results, indicating cosmic variance may be the cause of previous high density measurements. However, the number densities of UV-luminous galaxies at z = 12.5 are high compared to predictions from simulations. When examining the star formation rate density of galaxies at this period, our observations are still largely consistent with a constant star formation efficiency, are slightly lower than previous early estimations using JWST, and support galaxy driven reionization at z ≤ 8.

Keywords: high-redshift galaxies; lyman-break galaxies; galaxy photometry; luminosity function; reionization
Where Are the Extrasolar Mercuries?

We utilize observations of 16 white dwarf stars to calculate and analyze the oxidation states of the parent bodies accreting onto stars. Oxygen fugacity, which is a measure of overall oxidation state for rocks, is as important as pressure and temperature in determining the structure of a planet. We find that most of the extrasolar rocky bodies formed under oxidizing conditions, but that ∼1/4 of the polluted white dwarfs have compositions that are consistent with more reduced parent bodies. The difficulty in constraining the oxidation states of relatively reduced bodies is discussed and a model for the time-dependent evolution of the apparent oxygen fugacity for a hypothetical reduced body engulfed by a WD is investigated. The differences in diffusive fluxes of various elements through the WD envelope yield spurious inferred bulk elemental compositions and oxidation states of the accreting parent bodies under certain conditions. The worst case for biasing against detection of reduced bodies occurs for high effective temperatures. For moderate and low effective temperatures, the evidence for relatively reduced parent bodies is preserved under most circumstances for at least several characteristic lifetimes of the debris disk.

Keywords: white dwarf stars; exoplanets; extrasolar rocky planets; minor planets
Exemplary Merging Clusters: Weak-lensing and X-Ray Analysis of the Double Radio Relic, Merging Galaxy Clusters MACS J1752.0+4440 and ZWCL 1856.8+6616

The investigation of merging galaxy clusters that exhibit radio relics is strengthening our understanding of the formation and evolution of galaxy clusters, the nature of dark matter, the intracluster medium, and astrophysical particle acceleration. Each merging cluster provides only a single view of the cluster formation process, and the variety of merging clusters is vast. Clusters hosting double radio relics are rare and extremely important because they allow tight constraints on the merger scenario. We present a weak-lensing and X-ray analysis of MACS J1752.0+4440 (z = 0.365) and ZWCL 1856.8+6616 (z = 0.304), two double radio relic clusters. Our weak-lensing mass estimates show that each cluster is a major merger with approximately 1:1 mass ratio. The total mass of MACS J1752.0+4440 (ZWCL 1856.8+6616) is ${M}_{200}={14.7}_{-3.3}^{+3.8}\times {10}^{14}$ M⊙ ( ${M}_{200}={2.4}_{-0.7}^{+0.9}\times {10}^{14}$ M⊙). We find that these two clusters have comparable features in their weak-lensing and gas distributions, even though the systems have vastly different total masses. From the likeness of the X-ray morphologies and the remarkable symmetry of the radio relics, we propose that both systems underwent nearly head-on collisions. However, revelations from the hot-gas features and our multiwavelength data analysis suggest that ZWCL 1856.8+6618 is likely at a later merger phase than MACS J1752.0+4440. We postulate that the SW radio relic in MACS J1752.0+4440 is a result of particle reacceleration.

Keywords: galaxy clusters; shocks; weak gravitational lensing; dark matter; hubble space telescope
Unraveling the Thermodynamic Enigma between Fast and Slow Coronal Mass Ejections

Coronal mass ejections (CMEs) are the most energetic expulsions of magnetized plasma from the Sun that play a crucial role in space weather dynamics. This study investigates the diverse kinematics and thermodynamic evolution of two CMEs (CME1: 2011 September 24 and CME2: 2018 August 20) at coronal heights where thermodynamic measurements are limited. The peak 3D propagation speed of CME1 is high (1885 km s-1) with two-phase expansion (rapid and nearly constant), while the peak 3D propagation speed of CME2 is slow (420 km s-1) with only a gradual expansion. We estimate the distance-dependent variations in the polytropic index, heating rate, temperature, and internal forces implementing the revised FRIS model, taking inputs of 3D kinematics estimated from the graduated cylindrical shell model. We find CME1 exhibiting heat release during its early-rapid acceleration decrease and jumps to the heat-absorption state during its constant acceleration phase. In contrast to CME1, CME2 shows a gradual transition from the near-adiabatic to the heat-absorption state during its gradually increasing acceleration. Our analysis reveals that although both CMEs show differential heating, they experience heat absorption during their later propagation phases, approaching the isothermal state. The faster CME1 achieves an adiabatic state followed by an isothermal state at smaller distances from the Sun than the slower CME2. We also find that the expansion of CMEs is primarily influenced by centrifugal and thermal pressure forces, with the Lorentz force impeding expansion. Multiwavelength observations of flux-ropes at source regions support the FRIS-model-derived findings at initially observed lower coronal heights.

Keywords: solar coronal mass ejections
Mass and Angular Momentum Transport in a Gravitationally Unstable Protoplanetary Disk with Improved 3D Radiative Hydrodynamics

During early phases of a protoplanetary disk's life, gravitational instabilities (GIs) can produce significant mass transport, can dramatically alter disk structure, can mix and shock-process gas and solids, and may be instrumental in planet formation. We present a 3D grid-based radiative hydrodynamics study with varied resolutions of a 0.07 M ⊙ disk orbiting a 0.5 M ⊙ star as it settles over most of its radial extent into a quasi-steady asymptotic state that maintains approximate balance between heating produced by GIs and radiative cooling governed by realistic dust opacities. We assess disk stability criteria, thermodynamic properties, strengths of GIs, characteristics of density waves and torques produced by GIs, radial mass transport arising from these torques, and the level to which transport can be represented as local or nonlocal processes. Physical and thermal processes display distinct differences between inner optically thick and outer optically thin regions of the disk. In the inner region, gravitational torques are dominated by low-order Fourier components of the azimuthal mass distribution. These torques are strongly variable on the local dynamical time and are subject to rapid flaring presumably driven by recurrent swing amplification. In the outer region, m = 1 torques dominate. Ring-like structures exhibiting strong noncircular motions, and vortices develop near the inner edge between 8 and 14 au. We find that GI-induced spiral modes erupt in a chaotic manner over the whole low-Q part of the disk, with many spiral modes appearing and disappearing, producing gravitoturbulence, but dominated by fluctuating large-scale modes, very different from a simple α-disk.

Keywords: protoplanetary disks; gravitational instability; stellar accretion disks; hydrodynamics; hydrodynamical simulations
Emission Line Galaxies in the SHARDS Hubble Frontier Fields. II. Limits on Lyman-continuum Escape Fractions of Lensed Emission Line Galaxies at Redshifts 2 < z < 3.5

We present an investigation of escape fractions of UV photons from a unique sample of lensed low-mass emission line-selected galaxies at z < 3.5 found in the SHARDS Hubble Frontier Fields medium-band survey. We have used this deep imaging survey to locate 42 relatively low-mass galaxies down to log (M */M ⊙) = 7 in the redshift range 2.4 < z < 3.5 that are candidate line emitters. Using deep multiband Hubble UVIS imaging, we investigate the flux of escaping ionizing photons from these systems, obtaining 1σ upper limits of f rel esc ~ 7% for individual galaxies and <2% for stacked data. We measure potential escaping Lyman-continuum flux for two low-mass line emitters with values at ${f}_{\mathrm{esc}}^{\mathrm{rel}}={0.032}_{-0.009}^{+0.081}$ and ${0.021}_{-0.006}^{+0.101}$ , both detected at the ~3.2σ level. A detailed analysis of possible contamination reveals a <0.1% probability that these detections result from line-of-sight contamination. The relatively low Lyman-continuum escape fraction limit and the low fraction of systems detected are an indication that low-mass line-emitting galaxies may not be as important a source of reionization as hoped if these are analogs of reionization sources. We also investigate the structures of our galaxy sample, finding no evidence for a correlation of escape fraction with asymmetric structure.

Keywords: galaxy evolution
Extrapolation of Three-dimensional Magnetic Field Structure in Flare-productive Active Regions with Different Initial Conditions

Nonlinear force-free field (NLFFF) modeling has been extensively used as a tool to infer three-dimensional (3D) magnetic field structure. In this study, the dependency of the NLFFF calculation with respect to the initial guess of the 3D magnetic field is investigated. While major parts of the previous studies used the potential field as the initial guess in NLFFF modeling, we adopt linear force-free fields with different constant force-free alpha as the initial guesses. This method enables us to investigate the uniqueness of the magnetic field obtained by the NLFFF extrapolation with respect to the initial guess. The dependence of the initial conditions on NLFFF extrapolation is smaller in the strong magnetic field region. Therefore, the magnetic field at lower heights (<10 Mm) tends to be less affected by the initial conditions (correlation coefficient C > 0.9 with different initial conditions); although, the Lorentz force is concentrated at lower heights.

Keywords: active sun; solar active regions; solar active region velocity fields
A Distinct Population of Small Planets: Sub-Earths

The sizes of small planets are known to be bimodal, with a gap separating planets that have lost their primordial atmospheres (super-Earths) and the ones that retain them (mini-Neptunes). Here, we report evidence for another distinct population at smaller sizes. By focusing on planets orbiting around GK dwarfs inward of 16 days and correcting for observational completeness, we find that the number of super-Earths peaks around 1.4 Earth radii and disappears shortly below this size. Instead, a new population of planets (sub-Earths) appears to dominate at sizes below ∼1 Earth radius, with an occurrence that increases with decreasing size. This pattern is also observed in ultra-short-period planets. The end of super-Earths supports earlier claims that super-Earths and mini-Neptunes, planets that likely form in gaseous protoplanetary disks, have a narrow mass distribution. Sub-Earths, in contrast, can be described by a power-law mass distribution and may be explained by the theory of terrestrial planet formation. We therefore speculate that they are formed well after the gaseous disks have dissipated. The extension of these sub-Earths toward longer orbital periods, currently invisible, may be the true terrestrial analogs. This strongly motivates new searches.

Keywords: exoplanets
Quasi-thermal Noise Spectroscopy Analysis of Parker Solar Probe Data: Improved Electron Density Model for Solar Wind

We present a comprehensive analysis of electron density measurements in the solar wind using quasi-thermal noise (QTN) spectroscopy applied to data from the first 15 encounters of the Parker Solar Probe mission (2018 November-2023 March). Our methodology involves the identification of the plasma line frequency and the calculation of plasma density based on in situ measurements. By analyzing over 2.1 million data points, we derive a power-law model for electron density as a function of radial distance from the Sun in the range of 13 to 50 R ☉: n e(r) = (343,466 ± 19921) × r (-1.87±0.11). This model provides improved estimates for localizing interplanetary solar radio bursts. Moreover, obtained electron densities can be used for calibrating particle instruments on board the Parker Solar Probe. We discuss its limitations and potential for further refinement with additional Parker Solar Probe encounters.

Keywords: solar wind; space plasmas; radio spectroscopy
Multispacecraft Analysis of the Properties of Magnetohydrodynamic Fluctuations in Sub-Alfvénic Solar Wind Turbulence at 1 au

We present observations of three-dimensional magnetic power spectra in wavevector space to investigate the anisotropy and scalings of sub-Alfvénic solar wind turbulence at magnetohydrodynamic (MHD) scale using the Magnetospheric Multiscale spacecraft. The magnetic power distributions are organized in a new coordinate determined by wavevectors ( $\hat{{\boldsymbol{\kappa }}}$ ) and background magnetic field ( ${\widehat{{\boldsymbol{b}}}}_{0}$ ) in Fourier space. This study utilizes two approaches to determine wavevectors: the singular value decomposition method and multispacecraft timing analysis. The combination of the two methods allows an examination of the properties of magnetic field fluctuations in terms of mode compositions without any spatiotemporal hypothesis. Observations show that fluctuations (δ B ⊥1) in the direction perpendicular to $\hat{{\boldsymbol{\kappa }}}$ and ${\widehat{{\boldsymbol{b}}}}_{0}$ prominently cascade perpendicular to ${\widehat{{\boldsymbol{b}}}}_{0}$ , and such anisotropy increases with wavenumbers. The reduced power spectra of δ B ⊥1 follow Goldreich-Sridhar scalings: $\hat{P}({k}_{\perp })\propto {k}_{\perp }^{-5/3}$ and $\hat{P}({k}_{\parallel })\propto {k}_{\parallel }^{-2}$ . In contrast, fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane show isotropic behaviors: perpendicular power distributions are approximately the same as parallel distributions. The reduced power spectra of fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane follow the scalings $\hat{P}({k}_{\perp })\propto {k}_{\perp }^{-3/2}$ and $\hat{P}({k}_{\parallel })\propto {k}_{\parallel }^{-3/2}$ . Comparing frequency-wavevector spectra with theoretical dispersion relations of MHD modes, we find that δ B ⊥1 are probably associated with Alfvén modes. On the other hand, magnetic field fluctuations within the $\hat{k}{\hat{b}}_{0}$ plane more likely originate from fast modes based on their isotropic behaviors. The observations of anisotropy and scalings of different magnetic field components are consistent with the predictions of current compressible MHD theory. Moreover, for the Alfvénic component, the ratio of cascading time to the wave period is found to be a factor of a few, consistent with critical balance in the strong turbulence regime. These results are valuable for further studies of energy compositions of plasma turbulence and their effects on energetic particle transport.

Keywords: solar wind; interplanetary turbulence
Imaging the Milky Way with Millihertz Gravitational Waves

Modern astronomers enjoy access to all-sky images across a wide range of the electromagnetic spectrum from long-wavelength radio to high-energy gamma rays. The most prominent feature in many of these images is our own Galaxy, with different features revealed in each wave band. Gravitational waves (GWs) have recently been added to the astronomers' toolkit as a nonelectromagnetic messenger. To date, all identified GW sources have been extra-Galactic and transient. However, the Milky Way hosts a population of ultracompact binaries (UCBs), which radiate persistent GWs in the milliHertz band that is not observable with today's terrestrial gravitational-wave detectors. Space-based detectors such as the Laser Interferometer Space Antenna will measure this population and provide a census of their location, masses, and orbital properties. In this work, we will show how this data can be used to form a false-color image of the Galaxy that represents the intensity and frequency of the gravitational waves produced by the UCB population. Such images can be used to study the morphology of the Galaxy, identify interesting multimessenger sources through cross-matching, and for educational and outreach purposes.

Keywords: gravitational waves; gravitational wave astronomy; white dwarf stars; compact binary stars; astronomy image processing
TESS Re-observes the Young Multi-planet System TOI-451: Refined Ephemeris and Activity Evolution

We present a new analysis of the light curve of the young planet-hosting star TOI 451 in the light of new observations from TESS Cycle 3. Our joint analysis of the transits of all three planets, using all available TESS data, results in an improved ephemeris for TOI 451 b and TOI 451 c, which will help to plan follow-up observations. The updated mid-transit times are BJD-2,457,000 = ${1410.9896}_{-0.0029}^{+0.0032}$ , ${1411.7982}_{-0.0020}^{+0.0022}$ , and ${1416.63407}_{-0.00100}^{+0.00096}$ for TOI 451 b, c, and d, respectively, and the periods are ${1.8587028}_{-10e-06}^{+08e-06}$ , ${9.192453}_{-3.3e-05}^{+4.1e-05}$ , and ${16.364932}_{-3.5e-05}^{+3.6e-05}$ days. We also model the out-of-transit light curve using a Gaussian Process with a quasi-periodic kernel, and infer a change in the properties of the active regions on the surface of TOI 451 between TESS Cycles 1 and 3.

Keywords: exoplanets; stellar activity; transits
Peculiar Disk Behaviors of the Black Hole Candidate MAXI J1348-630 in the Hard State Observed by Insight-HXMT and Swift

We present a spectral study of the black hole candidate MAXI J1348-630 during its 2019 outburst, based on monitoring observations with Insight-HXMT and Swift. Throughout the outburst, the spectra are well fitted with power-law plus disk-blackbody components. In the soft-intermediate and soft states, we observed the canonical relation $L\propto {T}_{\mathrm{in}}^{4}$ between disk luminosity L and peak color temperature T in, with a constant inner radius R in (traditionally identified with the innermost stable circular orbit). At other stages of the outburst cycle, the behavior is more unusual, inconsistent with the canonical outburst evolution of black hole transients. In particular, during the hard rise, the apparent inner radius is smaller than in the soft state (and increasing), and the peak color temperature is higher (and decreasing). This anomalous behavior is found even when we model the spectra with self-consistent Comptonization models, which take into account the upscattering of photons from the disk component into the power-law component. To explain both anomalous trends at the same time, we suggest that the hardening factor for the inner-disk emission was larger than the canonical value of ≈1.7 at the beginning of the outburst. A more physical trend of radii and temperature evolution requires a hardening factor evolving from ≈3.5 at the beginning of the hard state to ≈1.7 in the hard-intermediate state. This could be evidence that the inner disk was in the process of condensing from the hot, optically thin medium and had not yet reached a sufficiently high optical depth for its emission spectrum to be described by the standard optically thick disk solution.

Keywords: x-ray binary stars; black hole physics; accretion; stellar accretion disks
Absorption Spectra of Electrified Hydrogen Molecules

Molecular hydrogen normally has only weak, quadrupole transitions between its rovibrational states, but in a static electric field it acquires a dipole moment and a set of allowed transitions. Here we use published ab initio calculations of the static electrical response tensors of the H2 molecule to construct the perturbed rovibrational eigensystem and its ground state absorptions. We restrict attention to two simple field configurations that are relevant to condensed hydrogen molecules in the interstellar medium (ISM): a uniform electric field and the field of a pointlike charge. The energy eigenstates are mixtures of vibrational and angular momentum eigenstates so there are many transitions that satisfy the dipole selection rules. We find that mixing is strongest among the states with high vibrational excitation, leading to hundreds of absorption lines across the optical and near-infrared. These spectra are very different from that of the field-free molecule, so if they appeared in astronomical data they would be difficult to assign. Furthermore, in a condensed environment the excited states likely have short lifetimes to internal conversion, giving the absorption lines a diffuse appearance. We therefore suggest electrified H2 as a possible carrier of the diffuse interstellar bands (DIBs). We further argue that in principle it may be possible to account for all of the DIBs with this one carrier. However, despite electrification, the transitions are not very strong and a large column of condensed H2 would be required, making it difficult to reconcile this possibility with our current understanding of the ISM.

Keywords: molecular physics; molecular spectroscopy; interstellar dust; interstellar dust extinction; diffuse interstellar bands; interstellar line absorption