adsabs/SciX_UAT_keywords huggingface dataset:
Identification of Inertial Modes in the Solar Convection Zone

The observation of global acoustic waves (p modes) in the Sun has been key to unveiling its internal structure and dynamics. A different kind of wave, known as sectoral Rossby modes, has been observed and identified, which potentially opens the door to probing internal processes that are inaccessible through p-mode helioseismology. Yet another set of waves, appearing as retrograde-propagating, equatorially antisymmetric vorticity waves, has also been observed but their identification remained elusive. Here, through a numerical model implemented as an eigenvalue problem, we provide evidence supporting the identification of those waves as a class of inertial eigenmodes, distinct from the Rossby-mode class, with radial velocities comparable to the horizontal ones deep in the convective zone but still small compared to the horizontal velocities toward the surface. We also suggest that the signature of tesseral-like Rossby modes might be present in recent observational data.

Keywords: astrophysical fluid dynamics; solar oscillations; solar rotation
The PHANGS-JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular Resolution in Nearby GalaxieS

The PHANGS collaboration has been building a reference data set for the multiscale, multiphase study of star formation and the interstellar medium (ISM) in nearby galaxies. With the successful launch and commissioning of JWST, we can now obtain high-resolution infrared imaging to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds (~5-50 pc). In Cycle 1, PHANGS is conducting an eight-band imaging survey from 2 to 21 μm of 19 nearby spiral galaxies. Optical integral field spectroscopy, CO(2-1) mapping, and UV-optical imaging for all 19 galaxies have been obtained through large programs with ALMA, VLT-MUSE, and Hubble. PHANGS-JWST enables a full inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains. When combined with Hubble catalogs of ~10,000 star clusters, MUSE spectroscopic mapping of ~20,000 H II regions, and ~12,000 ALMA-identified molecular clouds, it becomes possible to measure the timescales and efficiencies of the earliest phases of star formation and feedback, build an empirical model of the dependence of small dust grain properties on local ISM conditions, and test our understanding of how dust-reprocessed starlight traces star formation activity, all across a diversity of galactic environments. Here we describe the PHANGS-JWST Treasury survey, present the remarkable imaging obtained in the first few months of science operations, and provide context for the initial results presented in the first series of PHANGS-JWST publications.

Keywords: star formation; spiral galaxies; surveys; young star clusters; interstellar medium; polycyclic aromatic hydrocarbons; interstellar dust
Chemistry and Physics of a Low-metallicity Hot Core in the Large Magellanic Cloud

We here present the results of 0.1 pc scale observations in 250 and 350 GHz toward a newly-discovered hot molecular core in a nearby low-metallicity galaxy, the Large Magellanic Cloud (LMC), with the Atacama Large Millimeter/submillimeter Array. A variety of C/N/O/Si/S-bearing molecules are detected toward the high-mass young stellar object, ST16. A rotating protostellar envelope is for the first time detected outside our Galaxy by SO2 and 34SO lines. An outflow cavity is traced by CCH and CN. The isotope abundance of sulfur in the source is estimated to be 32S/34S = 17 and 32S/33S = 53 based on SO, SO2, and CS isotopologues, suggesting that both 34S and 33S are overabundant in the LMC. Rotation diagram analyses show that the source is associated with hot gas (>100 K) traced by high-excitation lines of CH3OH and SO2, as well as warm gas (∼50 K) traced by CH3OH, SO2, 34SO, OCS, and CH3CN lines. A comparison of molecular abundances between LMC and Galactic hot cores suggests that organic molecules (e.g., CH3OH, a classical hot core tracer) show a large abundance variation in low metallicity, where the present source is classified into an organic-poor hot core. Our astrochemical simulations suggest that different grain temperatures during the initial ice-forming stage would contribute to the chemical differentiation. In contrast, SO2 shows similar abundances within all of the known LMC hot cores, and the typical abundance roughly scales with the LMC's metallicity. Nitrogen-bearing molecules are generally less abundant in the LMC hot cores, except for NO. The present results suggest that chemical compositions of hot cores do not always simply scale with the metallicity.

Keywords: astrochemistry; dust continuum emission; interstellar molecules; protostars; large magellanic cloud; interstellar line emission; isotopic abundances; metallicity; star formation; submillimeter astronomy
Signatures of Tidal Disruption of the Hercules Ultrafaint Dwarf Galaxy

The Hercules ultrafaint dwarf galaxy (UFD) has long been hypothesized to be tidally disrupting, yet no conclusive evidence has been found for tidal disruption owing partly to difficulties in identifying Hercules member stars. In this work, we present a homogeneous reanalysis of new and existing observations of Hercules, including the detection of a new potential member star located ∼1° (∼1.7 kpc) west of the center of the system. In addition to measuring the line-of-sight velocity gradient, we compare predictions from dynamical models of stream formation to these observations. We report an updated velocity dispersion measurement based on 28 stars, ${1.9}_{-0.6}^{+0.6}$ km s‑1, which is significantly lower than previous measurements. We find that the line-of-sight velocity gradient is ${1.8}_{-1.8}^{+1.8}$ km s‑1 kpc along the major axis of Hercules, consistent with zero within 1σ. Our dynamical models of stream formation, on the other hand, can reproduce the morphology of the Hercules UFD, specifically the misalignment between the elongation and the orbital motion direction. Additionally, these dynamical models indicate that any radial velocity gradient from tidal disruption would be too small, ${0.00}_{-0.91}^{+0.97}$ km s‑1 kpc, to be detectable with current sample sizes. Combined with our analysis of the tidal radius evolution of the system as a function of its orbital phase, we argue that it is likely that Hercules is indeed currently undergoing tidal disruption in its extended stellar halo with a line-of-sight velocity gradient too small to be detected with current observational data sets. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile.

Keywords: dwarf galaxies; galaxy dynamics; galaxy kinematics; radial velocity
Evidence for Ubiquitous Carbon Grain Destruction in Hot Protostellar Envelopes

Earth is deficient in carbon and nitrogen by up to ~4 orders of magnitude compared with the Sun. Destruction of (carbon- and nitrogen-rich) refractory organics in the high-temperature planet-forming regions could explain this deficiency. Assuming a refractory cometary composition for these grains, their destruction enhances nitrogen-containing, oxygen-poor molecules in the hot gas (≳300 K) after the initial formation and sublimation of these molecules from oxygen-rich ices in the warm gas (~150 K). Using observations of 37 high-mass protostars with the Atacama Large Millimeter/submillimeter Array, we find that oxygen-containing molecules (CH3OH and HNCO) systematically show no enhancement in their hot component. In contrast, nitrogen-containing, oxygen-poor molecules (CH3CN and C2H3CN) systematically show an enhancement of a factor ~5 in their hot component, pointing to additional production of these molecules in the hot gas. Assuming only thermal excitation conditions, we interpret these results as a signature of destruction of refractory organics, consistent with the cometary composition. This destruction implies a higher C/O and N/O in the hot gas than the warm gas, while the exact values of these ratios depend on the fraction of grains that are effectively destroyed. This fraction can be found by future chemical models that constrain C/O and N/O from the abundances of minor carbon, nitrogen, and oxygen carriers presented here.

Keywords: astrochemistry; protostars; chemical abundances; interferometry
A New Candidate Transitional Millisecond Pulsar in the Subluminous Disk State: 4FGL J0407.7-5702

We report the discovery of a variable optical and X-ray source within the error ellipse of the previously unassociated Fermi Large Area Telescope γ-ray source 4FGL J0407.7-5702. A 22 ks observation from XMM-Newton/European Photon Imaging Camera (EPIC) shows an X-ray light curve with rapid variability and flaring. The X-ray spectrum is well fit by a hard power law with Γ = 1.7. Optical photometry taken over several epochs is dominated by aperiodic variations of moderate amplitude. Optical spectroscopy with Southern Astrophysical Research (SOAR) and Gemini reveals a blue continuum with broad and double-peaked H and He emission, as expected for an accretion disk around a compact binary. Overall, the optical, X-ray, and γ-ray properties of 4FGL J0407.7-5702 are consistent with a classification as a transitional millisecond pulsar in the subluminous disk state. We also present evidence that this source is more distant than other confirmed or candidate transitional millisecond pulsar binaries, and that the ratio of X-ray to γ-ray flux is a promising tool to help identify such binaries, indicating that a more complete census for these rare systems is becoming possible.

Keywords: neutron stars; gamma-rays
Application of the Disk Instability Model to All Quasiperiodic Eruptions

After the first quasiperiodic eruption (QPE; GSN 069) was reported in 2019, four other sources have been identified as a QPE or a candidate. However, the physics behind QPEs is still unclear, although several models have been proposed. Pan et al. proposed an instability model for an accretion disk with magnetically driven outflows in the first QPE of GSN 069, which is able to reproduce both the light curve and the evolution of the spectra fairly well. In this work, we extend this model to all QPEs. We improve the calculations of the spectrum of the disk by introducing a hardening factor, which is caused by a deviation of opacity from a blackbody. We find that the light curves and evolution of the spectra of the four QPEs and candidates can all be well reproduced by our model calculations.

Keywords: magnetic fields; galaxy accretion disks; active galactic nuclei
CHIMERA: A Massively Parallel Code for Core-collapse Supernova Simulations

We provide a detailed description of the CHIMERA code, a code developed to model core collapse supernovae (CCSNe) in multiple spatial dimensions. The CCSN explosion mechanism remains the subject of intense research. Progress to date demonstrates that it involves a complex interplay of neutrino production, transport, and interaction in the stellar core, three-dimensional stellar core fluid dynamics and its associated instabilities, nuclear burning, and the fundamental physics of the neutrino-stellar core weak interactions and the equations of state of all stellar core constituents—particularly, the nuclear equation of state associated with core nucleons, both free and bound in nuclei. CHIMERA, by incorporating detailed neutrino transport, realistic neutrino-matter interactions, three-dimensional hydrodynamics, realistic nuclear, leptonic, and photonic equations of state, and a nuclear reaction network, along with other refinements, can be used to study the role of neutrino radiation, hydrodynamic instabilities, and a variety of input physics in the explosion mechanism itself. It can also be used to compute observables such as neutrino signatures, gravitational radiation, and the products of nucleosynthesis associated with CCSNe. The code contains modules for neutrino transport, multidimensional compressible hydrodynamics, nuclear reactions, a variety of neutrino interactions, equations of state, and modules to provide data for post-processing observables such as the products of nucleosynthesis, and gravitational radiation. CHIMERA is an evolving code, being updated periodically with improved input physics and numerical refinements. We detail here the current version of the code, from which future improvements will stem, which can in turn be described as needed in future publications.

Keywords: core-collapse supernovae; computational methods; reaction rates; radiative transfer simulations; supernova neutrinos; hydrodynamical simulations; nucleosynthesis
HST Survey of the Orion Nebula Cluster in the H2O 1.4 μm Absorption Band. I. A Census of Substellar and Planetary-mass Objects

In order to obtain a complete census of the stellar and substellar population, down to a few ${M}_{\mathrm{Jup}}$ in the ∼1 Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4 μm H2O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m130 = 14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen-burning limit mass ( $M\simeq 0.072\,{M}_{\odot }$ ) at ∼1 Myr. Of these, however, only 742 sources have a negative F130M-F139N color index, indicative of the presence of H2O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T ≲ 2850 K at an assumed 1 Myr cluster age. On our color-magnitude diagram (CMD), this population of sources with H2O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M-F139N color index and can be traced down to the sensitivity limit of our survey, m130 ≃ 21.5, corresponding to a 1 Myr old ≃3 ${M}_{\mathrm{Jup}}$ planetary-mass object under about 2 mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ∼1 ${M}_{\mathrm{Jup}}$ fail to reproduce the observed H2O color index at M ≲ 20 ${M}_{\mathrm{Jup}}$ . We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.

Keywords: pre-main sequence stars; brown dwarfs; young star clusters
Progenitor Stars Calculated with Small Reaction Networks should not be Used as Initial Conditions for Core Collapse

Core collapse initial conditions are a bottleneck in understanding the explosion mechanism(s) of massive stars. Stellar evolution codes struggle after carbon burning, and either stop or adopt numerical simplifications missing crucial physics. The use of small nuclear reaction networks (NRN) that account for energy production but bypass weak reactions is typical, but insufficient to study the dynamics of the collapse. We advise against the use of progenitors computed with small NRN in expensive multidimensional simulations of core collapse, bounce, (jet formation), and explosion.

Keywords: massive stars; stellar rotation; supernovae; gamma-ray bursts
Discovery of a Bimodal Environmental Distribution of Compact Ellipticals in the Local Universe

Low-mass compact stellar systems (CSSs; M ⋆ < 1010 M ⊙) are thought to be a mixed bag of objects with various formation mechanisms. Previous surveys of CSSs were biased to relatively high-density environments and cannot provide a complete view of the environmental dependence of the formation of CSSs. We conduct the first-ever unbiased flux-limited census of nearby quiescent CSSs over a total sky area of ~200 deg2 observed by the GAMA spectroscopic survey. The complete sample includes 82 quiescent CSSs, of which 85% fall within the stellar mass range of classical compact ellipticals (cEs). By quantifying the local environment with the normalized projected distance D/R vir to the nearest luminous neighboring galaxy, we find that these CSSs have a bimodal D/R vir distribution, with one group peaking near ~0.1 × R vir (satellite) and the other peaking near ~10 × R vir (field). In contrast to the CSSs, ordinary quiescent galaxies of similar masses have a unimodal D/R vir distribution. Satellite CSSs are older and more metal-rich than field CSSs on average. The bimodal D/R vir distribution of quiescent CSSs reinforces the existence of two distinct formation channels (tidal stripping and born-to-be) for cEs and may be understood in two mutually inclusive perspectives, i.e., substantial tidal stripping happens only when satellite galaxies travel sufficiently close to their massive hosts, and there exists an excess of high-density cE-bearing subhalos close to massive halos.

Keywords: compact dwarf galaxies; compact galaxies; galaxy formation; stellar populations; tidal interaction; elliptical galaxies
CosTuuM: Polarized Thermal Dust Emission by Magnetically Oriented Spheroidal Grains

We present the new open-source C++-based Python library COSTUUM that can be used to generate infrared absorption and emission coefficients for arbitrary mixtures of spheroidal dust grains that are (partially) aligned with a magnetic field. We outline the algorithms underlying the software, demonstrate the accuracy of our results using benchmarks from literature, and use our tool to investigate some commonly used approximative recipes. We find that the linear polarization fraction for a partially aligned dust grain mixture can be accurately represented by an appropriate linear combination of perfectly aligned grains and grains that are randomly oriented, but that the commonly used picket fence alignment breaks down for short wavelengths. We also find that for a fixed dust grain size, the absorption coefficients and linear polarization fraction for a realistic mixture of grains with various shapes cannot both be accurately represented by a single representative grain with a fixed shape, but that instead an average over an appropriate shape distribution should be used. Insufficient knowledge of an appropriate shape distribution is the main obstacle in obtaining accurate optical properties. COSTUUM is available as a standalone Python library and can be used to generate optical properties to be used in radiative transfer applications.

Keywords: radiative transfer simulations; dust continuum emission; magnetic fields; interstellar dust; polarimetry
Observations of Thomson Scattering from a Loop-prominence System

We describe observations of the white-light structures in the low corona following the X8.2 flare SOL 2017-09-10, as observed in full Stokes parameters by the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory. These data show both bright loops and a diffuse emission region above them. We interpret the loops as the white-light counterpart of a classical loop-prominence system, intermediate between the hot X-ray loops and coronal rain. The diffuse emission external to the loops is linearly polarized and has a natural interpretation in terms of Thomson scattering from the hot plasma seen prior to its cooling and recombination. The polarimetric data from HMI enable us to distinguish this contribution of scattering from the HMI pseudocontinuum measurement, and to make a direct estimation of the coronal mass in the polarized source. For a snapshot at 16:19 UT, we estimate a mass 8 × 1014 g. We further conclude that the volumetric filling factor of this source is near unity.

Keywords: solar flares
Black Hole Growth and Feedback in Isolated ROMULUS25 Dwarf Galaxies

We investigate the effects of massive black hole growth on the structural evolution of dwarf galaxies within the ROMULUS25 cosmological hydrodynamical simulation. We study a sample of 205 central, isolated dwarf galaxies with stellar masses ${M}_{\mathrm{star}}\lt {10}^{10}{M}_{\odot }$ and a central BH. We find that the local MBH-Mstar relation exhibits a high degree of scatter below Mstar < 1010M⊙, which we use to classify BHs as overmassive or undermassive relative to their host Mstar. Within isolated dwarf galaxies, only 8% of undermassive BHs ever undergo a BH merger, while 95% of overmassive BHs grow through a mixture of BH mergers and accretion. We find that isolated dwarf galaxies that host overmassive BHs also follow different evolutionary tracks relative to their undermassive BH counterparts, building up their stars and dark matter earlier and experiencing star formation suppression starting around z = 2. By z = 0.05, overmassive BH hosts above Mstar > 109M⊙ are more likely to exhibit lower central stellar mass density, lower H I gas content, and lower star formation rates than their undermassive BH counterparts. Our results suggest that overmassive BHs in isolated galaxies above Mstar > 109M⊙ are capable of driving feedback, in many cases suppressing and even quenching star formation by late times.

Keywords: supermassive black holes; dwarf galaxies; black hole physics; n-body simulations
Pileups and Migration Rates for Planets in Low-mass Disks

We investigate how planets interact with viscous accretion disks, in the limit that the disk is sufficiently low mass that the planet migrates more slowly than the disk material. In that case, the disk's surface density profile is determined by the disk being in viscous steady state (VSS) while overflowing the planet's orbit. We compute the VSS profiles with 2D hydrodynamical simulations, and show that disk material piles up behind the planet, with the planet effectively acting as a leaky dam. Previous 2D hydrodynamical simulations missed the pileup effect because of incorrect boundary conditions, while previous 1D models greatly overpredicted the pileup due to the neglect of nonlocal deposition. Our simulations quantify the magnitude of the pileup for a variety of planet masses and disk viscosities. We also calculate theoretically the magnitude of the pileup for moderately deep gaps, showing good agreement with simulations. For very deep gaps, current theory is inadequate, and we show why and what must be understood better. The pileup is important for two reasons. First, it is observable in directly imaged protoplanetary disks, and hence can be used to diagnose the mass of a planet that causes it or the viscosity within the disk. Second, it determines the planet's migration rate. Our simulations determine a new Type-II migration rate (valid for low-mass disks), and show how it connects continuously with the well-verified Type-I rate.

Keywords: protoplanetary disks; circumstellar disks; planet formation