adsabs/SciX_UAT_keywords huggingface dataset:
Shock and Cosmic-Ray Chemistry Associated with the Supernova Remnant W28

Supernova remnants (SNRs) exert a strong influence on the physics and chemistry of the nearby molecular clouds through shock waves and the cosmic rays (CRs) they accelerate. To investigate the SNR–cloud interaction in the prototype interacting SNR W28 (G6.4‑0.1), we present new observations of the HCO+, $\mathrm{HCN}$ , and HNC J = 1–0 lines, supplemented by archival data of CO isotopes, N2H+ and H13CO+. We compare the spatial distribution and spectral line profiles of different molecular species. Using the local thermodynamic equilibrium assumption, we obtain an abundance ratio of N(HCO+)/N(CO) ∼10‑4 in the northeastern shocked cloud, which is higher by an order of magnitude than the values in unshocked clouds. This can be accounted for by the chemistry jointly induced by shock and CRs, with the physical parameters previously obtained from observations: preshock density n H ∼ 2 × 105 cm‑3, CR ionization rate ζ = 2.5 × 10‑15 s‑1, and shock velocity V s = 15–20 km s‑1. Toward a point outside the northeastern boundary of W28 with a known high CR ionization rate, we estimate the abundance ratio N(HCO+)/N(N2H+) ≈ 0.6–3.3, which can be reproduced by a chemical simulation if a high density n H ∼ 2 × 105 cm‑3 is adopted.

Keywords: molecular clouds; supernova remnants; cosmic rays; shocks; abundance ratios
VLA Limits on Intermediate-mass Black Holes in 19 Massive Globular Clusters

The NSF's Karl G. Jansky Very Large Array (VLA) was used at 3 cm to search for accretion signatures from intermediate-mass black holes (IMBHs) in 19 globular star clusters (GCs) in NGC 3115, an early-type galaxy at a distance of 9.4 Mpc. The 19 GCs have stellar masses M⋆ ∼ (1.1-2.7) × 106 M⊙, with a mean $\overline{{M}_{\star }}\sim 1.8\times {10}^{6}\,{M}_{\odot }$ . None were detected. An IMBH accretion model was applied to the individual GCs and their radio stack. The radio-stacked GCs have an IMBH mass $\overline{{M}_{\mathrm{IMBH}}}\lt 1.7\times {10}^{5}\,{M}_{\odot }$ and mass fraction $\overline{{M}_{\mathrm{IMBH}}}/\overline{{M}_{\star }}\lt 9.5 \% $ , with each limit being uncertain by a factor of about 2.5. The latter limit contrasts with the extremes of some stripped nuclei, suggesting that the set of stacked GCs in NGC 3115 is not a set of such nuclei. The radio luminosities of the individual GCs correspond to X-ray luminosities LX < (3.3-10) × 1038 erg s-1, with a factor of about 2.5 uncertainty. These limits predicted for putative IMBHs in the GCs are consistent with extant Chandra observations. Finally, a simulated observation with a next-generation VLA demonstrates that accretion signatures from IMBHs in GCs can be detected in a radio-only search, yet they elude detection in an X-ray-only search due to confusion from X-ray binaries in the GCs.

Keywords: intermediate-mass black holes; early-type galaxies; globular star clusters; aperture synthesis; accretion
Sustained Kozai-Lidov Oscillations in Misaligned Circumstellar Gas Disks

A disk around one component of a binary star system with sufficiently high inclination can undergo Kozai-Lidov (KL) oscillations during which the disk inclination and disk eccentricity are exchanged. Previous studies show that without a source of accretion, KL unstable disks exhibit damped oscillations, due to viscous dissipation, that leave the disk stable near or below the critical inclination for KL oscillations. With three-dimensional hydrodynamical simulations we show that a highly misaligned circumbinary disk that flows onto the binary components forms highly inclined circumstellar disks around each component. We show that a continuous infall of highly inclined material allows the KL oscillations to continue. The KL disk oscillations produce shocks and eccentricity growth in the circumstellar disks that affect the conditions for planet formation.

Keywords: binary stars; stellar accretion disks; exoplanet formation
Temperature Structure of the Pipe Nebula Studied by the Intensity Anomaly of the OH 18 cm Transition

We present observations of the four hyperfine structure components of the OH 18 cm transition (1612, 1665, 1667, and 1720 MHz) toward a filamentary dark cloud, the Pipe nebula, with the Green Bank Telescope. A statistical equilibrium analysis is applied to the spectra, and the kinetic temperature of a diffuse molecular gas surrounding dense cores is determined accurately; the derived temperature ranges from 40 to 75 K. From this result, we assess the heating effect on the filamentary structure of the nebula's "stem" region due to UV photons from a nearby star θ-Ophiuchi and a possible filament-filament collision in the interface of the "stem" and "bowl" regions. In the stem region, the gas kinetic temperature is found to be almost independent of the apparent distance from θ-Ophiuchi: the UV-heating effect by the star is not visible. On the other hand, the gas kinetic temperature is raised, as high as ∼75 K, at the interface of the two filamentary structures. This result provides us with additional support for the filament-filament collision scenario in the Pipe nebula.

Keywords: molecular clouds; interstellar molecules
Magnetic Fields in the Horsehead Nebula

We present the first polarized dust emission measurements of the Horsehead Nebula, obtained using the POL-2 polarimeter on the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera on the James Clerk Maxwell Telescope. The Horsehead Nebula contains two submillimeter sources: a photodissociation region (PDR; SMM1) and a starless core (SMM2). We see well-ordered magnetic fields in both sources. We estimated plane-of-sky magnetic field strengths of 56 ± 9 and 129 ± 21 μG in SMM1 and SMM2, respectively, and obtained mass-to-flux ratios and Alfvén Mach numbers of less than 0.6, suggesting that the magnetic field can resist gravitational collapse and that magnetic pressure exceeds internal turbulent pressure in these sources. In SMM2, the kinetic and gravitational energies are comparable to one another, but less than the magnetic energy. We suggest a schematic view of the overall magnetic field structure in the Horsehead Nebula. Magnetic field lines in SMM1 appear to have been compressed and reordered during the formation of the PDR, while the likely more-embedded SMM2 may have inherited its field from that of the pre-shock molecular cloud. The magnetic fields appear to currently play an important role in supporting both sources.

Keywords: molecular clouds; star formation; magnetic fields; polarimetry; submillimeter astronomy
DI Herculis Revisited: Starspots, Gravity Darkening, and 3D Obliquities

DI Herculis is an eclipsing binary famous for a longstanding disagreement between theory and observation of the apsidal precession rate, which was resolved when both stars were found to be severely misaligned with the orbit. We used data from the Transiting Exoplanet Survey Satellite (TESS) to refine our knowledge of the stellar obliquities and sharpen the comparison between the observed and theoretical precession rates. The TESS data show variations with a 1.07 day period, which we interpret as rotational modulation from starspots on the primary star. This interpretation is supported by the detection of photometric anomalies during primary eclipses consistent with starspot crossings. The secondary eclipse light curve shows a repeatable asymmetry that we interpret as an effect of gravity darkening. By combining the TESS data with previously obtained data, we determined the three-dimensional spin directions of both stars. Using this information, the updated value of the theoretical apsidal precession rate (including the effects of tides, rotation, and general relativity) is ${1.35}_{-0.50}^{+0.58}$ arcsec cycle-1. The updated value of the observed rate (after including new TESS eclipse times) is ${1.41}_{-0.28}^{+0.39}$ arcsec cycle-1. Given the agreement between the observed and theoretical values, we fitted all the relevant data simultaneously, assuming the theory is correct. This allowed us to place tighter constraints on the stellar obliquities, which are ${75}_{-3}^{+3}$ and ${80}_{-3}^{+3}$ degrees for the primary and secondary stars, respectively.

Keywords: detached binary stars; eclipsing binary stars; gravity darkening
Selection of Massive Evolved Galaxies at 3 ≤ z ≤ 4.5 in the CANDELS Fields

Using the CANDELS photometric catalogs for the Hubble Space Telescope/ACS and WFC3, we identified massive evolved galaxies at 3 < z < 4.5 employing three different selection methods. We find the comoving number density of these objects to be ∼2 × 10-5 and 8 × 10-6 Mpc-3 after correction for completeness for two redshift bins centered at z = 3.4, 4.7. We quantify a measure of how much confidence we should have for each candidate galaxy from different selections and what the conservative error estimates propagated into our selection are. Then we compare the evolution of the corresponding number densities and their stellar mass density with numerical simulations, semianalytical models, and previous observational estimates, which shows slight tension at higher redshifts as the models tend to underestimate the number and mass densities. By estimating the average halo masses of the candidates (Mh ≈ 4.2, 1.9, and 1.3 × 1012 M⊙ for redshift bins centered at z = 3.4, 4.1, and 4.7), we find them to be consistent with halos that were efficient in turning baryons to stars, relatively immune to the feedback effects, and on the verge of transition into hot-mode accretion. This can suggest the relative cosmological starvation of the cold gas followed by an overconsumption phase in which the galaxy rapidly consumes the available cold gas as one of the possible drivers for the quenching of the massive evolved population at high redshift.

Keywords: high-redshift galaxies; galaxy evolution; galaxies; extragalactic astronomy
The Influence of Heavy Cosmic Rays in Energy Deposition in Molecular Clouds Employing the GEANT4 Code and Voyager I Data

Galactic and extragalactic cosmic rays fully illuminate and trigger several physical and physicochemical changes in molecular clouds (MCs), including gas and grain heating, molecular destruction and formation, and molecular and atomic desorption (sputtering) from dust/ices to gas phase. Besides the major component in cosmic ray inventory (in flux) being electrons, protons, and alphas, particles with larger atomic numbers have a higher rate of energy delivery (due to richer cosmic ray showers) than the lighter particles, and this may add extra energy input into MCs. To understand this issue, we perform complementary calculations to the previous work on MCs, now adding the heavy ions (12 ≤ Z ≤ 29) in the cosmic ray incoming inventory. Once more, the calculations were performed employing the Monte Carlo toolkit GEANT4 code (considering nuclear and hadron physics). We observe that most projectiles in the heavy ion group have lower deposited energies (roughly 10 times less) than iron with the exception of magnesium (Z = 12) and silicon (Z = 14) which are about double. Cobalt presents the lowest deposited energies with respect to iron (only 0.5%). The total energy deposition in the current model was only roughly 10% higher (outer layers) and virtually the same at the center of the cloud when compared with the previous model (with only protons + alphas + electrons sources). The results show that energy deposition by heavy ions is small compared with the values from light particles, and also suggest a very low temperature enhancement due to heavy ions within the MC, being the protons the dominant agent in the energy delivery and also in the cloud's heating.

Keywords: cosmic rays
A Kiloparsec-scale Molecular Wave in the Inner Galaxy: Feather of the Milky Way?

We report the discovery of a velocity coherent, kiloparsec-scale molecular structure toward the Galactic center region with an angular extent of 30° and an aspect ratio of 60:1. The kinematic distance of the CO structure ranges between 4.4 and 6.5 kpc. Analysis of the velocity data and comparison with the existing spiral arm models support that a major portion of this structure is either a subbranch of the Norma arm or an interarm giant molecular filament, likely to be a kiloparsec-scale feather (or spur) of the Milky Way, similar to those observed in nearby spiral galaxies. The filamentary cloud is at least 2.0 kpc in extent, considering the uncertainties in the kinematic distances, and it could be as long as 4 kpc. The vertical distribution of this highly elongated structure reveals a pattern similar to that of a sinusoidal wave. The exact mechanisms responsible for the origin of such a kiloparsec-scale filament and its wavy morphology remains unclear. The distinct wave-like shape and its peculiar orientation makes this cloud, named as the Gangotri wave, one of the largest and most intriguing structures identified in the Milky Way.

Keywords: galaxy kinematics; galaxy structure; interstellar medium; giant molecular clouds; submillimeter astronomy
TESS Hunt for Young and Maturing Exoplanets (THYME). X. A Two-planet System in the 210 Myr MELANGE-5 Association

Young (<500 Myr) planets are critical to studying how planets form and evolve. Among these young planetary systems, multiplanet configurations are particularly useful, as they provide a means to control for variables within a system. Here, we report the discovery and characterization of a young planetary system, TOI-1224. We show that the planet host resides within a young population we denote as MELANGE-5. By employing a range of age-dating methods—isochrone fitting, lithium abundance analysis, gyrochronology, and Gaia excess variability—we estimate the age of MELANGE-5 to be 210 ± 27 Myr. MELANGE-5 is situated in close proximity to previously identified younger (80–110 Myr) associations, Crius 221 and Theia 424/Volans-Carina, motivating further work to map out the group boundaries. In addition to a planet candidate detected by the TESS pipeline and alerted as a TESS object of interest, TOI-1224 b, we identify a second planet, TOI-1224 c, using custom search tools optimized for young stars (Notch and LOCoR). We find that the planets are 2.10 ± 0.09 R ⊕ and 2.88 ± 0.10 R ⊕ and orbit their host star every 4.18 and 17.95 days, respectively. With their bright (K = 9.1 mag), small (R * = 0.44 R ⊙), and cool (T eff = 3326 K) host star, these planets represent excellent candidates for atmospheric characterization with JWST.

Keywords: exoplanet astronomy; transit photometry; stellar ages; young star clusters; stellar activity; transit timing variation method
Tracking Nonradial Outflows in Extreme Ultraviolet and White Light Solar Images

Understanding the solar corona requires knowledge of its dynamics through its various layers and subsequent connectivity to the heliosphere. This requires understanding the nature of the outflows and the physical transitions through the middle corona (~1.5-6.0 R s ). While this region is still inaccessible to in situ measurements, remote sensing observations are available, but their interpretation can be controversial due to line-of-sight effects and the nonradial motion of outflowing structures close to the Sun (≤3.0 R s ). In this work, we describe a method to mitigate these challenges by generating nonradial height-time profiles of outflows by using advanced image processing techniques. The northern and southern boundaries of a large equatorial streamer during the 2008 solar minimum were identified in STEREO/SECCHI solar images, using two different methodologies based on thresholds of brightness and piecewise polynomial function fitting. To address line-of-sight issues, we used tomographic reconstruction of the 3D distribution of the coronal electron density based on SECCHI/COR2 images. Spectral analysis of the time series of the position angle of the streamer boundary revealed its oscillatory nature at some heights at 36-48 and 10.5-14.6 hr. Dividing the distance between the northern and southern streamer boundaries in equal parts at each height, we obtained nonradial height-time paths from which we generated nonradial profiles of corona/solar wind plasma outflow. We tracked outflows as they moved uninterruptedly from the Sun in EUVI, through COR1 and into COR2. Finally, we discuss the preliminary results of nonradial plane-of-sky velocities for a coronal mass ejection and two small-scale features.

Keywords: solar corona; solar wind; astronomical techniques; quiet sun
Observing the Sun as a Star: Design and Early Results from the NEID Solar Feed

Efforts with extreme-precision radial velocity (EPRV) instruments to detect small-amplitude planets are largely limited, on many timescales, by the effects of stellar variability and instrumental systematics. One avenue for investigating these effects is the use of small solar telescopes which direct disk-integrated sunlight to these EPRV instruments, observing the Sun at high cadence over months or years. We have designed and built a solar feed system to carry out "Sun-as-a-star" observations with NEID, a very high precision Doppler spectrometer recently commissioned at the WIYN 3.5 m Telescope at Kitt Peak National Observatory. The NEID solar feed has been taking observations nearly every day since 2020 December; data is publicly available at the NASA Exoplanet Science Institute NEID Solar Archive: https://neid.ipac.caltech.edu/search_solar.php. In this paper, we present the design of the NEID solar feed and explanations behind our design intent. We also present early radial velocity (RV) results which demonstrate NEID's RV stability on the Sun over 4 months of commissioning: 0.66 m s-1 rms under good sky conditions and improving to 0.41 m s-1 rms under best conditions.

Keywords: exoplanets; radial velocity; solar telescopes; solar activity
JWST/MIRI Detection of Suprathermal OH Rotational Emissions: Probing the Dissociation of the Water by Lyα Photons near the Protostar HOPS 370

Using the MIRI medium-resolution spectrometer on JWST, we have detected pure rotational, suprathermal OH emissions from the vicinity of the intermediate-mass protostar HOPS 370 (OMC2/FIR3). These emissions are observed from shocked knots in a jet/outflow and originate in states of rotational quantum number as high as 46 that possess excitation energies as large as E U /k = 4.65 × 104 K. The relative strengths of the observed OH lines provide a powerful diagnostic of the ultraviolet radiation field in a heavily extinguished region (A V ∼ 10–20) where direct UV observations are impossible. To high precision, the OH line strengths are consistent with a picture in which the suprathermal OH states are populated following the photodissociation of water in its $\tilde{B}-X$ band by ultraviolet radiation produced by fast (∼80 km s‑1) shocks along the jet. The observed dominance of emission from symmetric ( $A^{\prime} $ ) OH states over that from antisymmetric (A″) states provides a distinctive signature of this particular population mechanism. Moreover, the variation of intensity with rotational quantum number suggests specifically that Lyα radiation is responsible for the photodissociation of water, an alternative model with photodissociation by a 104 K blackbody being disfavored at a high level of significance. Using measurements of the Brα flux to estimate the Lyα production rate, we find that ∼4% of the Lyα photons are absorbed by water. Combined with direct measurements of water emissions in the ν 2 = 1 ‑ 0 band, the OH observations promise to provide key constraints on future models for the diffusion of Lyα photons in the vicinity of a shock front.

Keywords: protostars; infrared astronomy; molecular gas
Neptune's Moon Triton: Continuing Surface Seasonal Volatile Transport

Observations of Triton's rotational light curve from Table Mountain Observatory in 2017 show that volatile transport is continuing on its surface. Changes in the light curve are consistent with sustained increases in albedo in two patches near the equator at longitudes of ~120° and ~280°, as first reported by Bauer et al. based on observations obtained with the Hubble Space Telescope. An early observation of Triton's visual albedo shows a substantially lower albedo in the past, when the northern polar region was visible. This result confirms the hypothesis of Moore & Spencer and Spencer & Moore of a net flux of volatile material into the southern hemisphere of Triton over much of the satellite's history and up to the present. The averaged V-band geometric albedo of Triton has been stable over the past three decades. The color of Triton has also been stable during the past decade.

Keywords: triton; trans-neptunian objects; small solar system bodies; neptunian satellites; neptune
Active Galactic Nucleus Quenching in Simulated Dwarf Galaxies

We examine the quenching characteristics of 328 isolated dwarf galaxies $\left({10}^{8}\lt {M}_{\mathrm{star}}/{M}_{\odot }\lt {10}^{10}\right)$ within the ROMULUS25 cosmological hydrodynamic simulation. Using mock-observation methods, we identify isolated dwarf galaxies with quenched star formation and make direct comparisons to the quenched fraction in the NASA Sloan Atlas (NSA). Similar to other cosmological simulations, we find a population of quenched, isolated dwarf galaxies below M star < 109 M ⊙ not detected within the NSA. We find that the presence of massive black holes (MBHs) in ROMULUS25 is largely responsible for the quenched, isolated dwarfs, while isolated dwarfs without an MBH are consistent with quiescent fractions observed in the field. Quenching occurs between z = 0.5-1, during which the available supply of star-forming gas is heated or evacuated by MBH feedback. Mergers or interactions seem to play little to no role in triggering the MBH feedback. At low stellar masses, M star ≲ 109.3 M ⊙, quenching proceeds across several Gyr as the MBH slowly heats up gas in the central regions. At higher stellar masses, M star ≳ 109.3 M ⊙, quenching occurs rapidly within 1 Gyr, with the MBH evacuating gas from the central few kpc of the galaxy and driving it to the outskirts of the halo. Our results indicate the possibility of substantial star formation suppression via MBH feedback within dwarf galaxies in the field. On the other hand, the apparent overquenching of dwarf galaxies due to MBH suggests that higher-resolution and/or better modeling is required for MBHs in dwarfs, and quenched fractions offer the opportunity to constrain current models.

Keywords: dwarf galaxies; supermassive black holes; star formation; active galaxies; galaxy quenching; hydrodynamical simulations
The ALMaQUEST Survey. XII. Dense Molecular Gas as Traced by HCN and HCO+ in Green Valley Galaxies

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of two dense gas tracers, HCN (1‑0) and HCO+ (1-0) for three galaxies in the green valley and two galaxies on the star-forming main sequence with comparable molecular gas fractions as traced by the CO (1‑0) emissions, selected from the ALMaQUEST survey. We investigate whether the deficit of molecular gas star formation efficiency (SFEmol) that leads to the low specific star formation rate (sSFR) in these green valley galaxies is due to a lack of dense gas (characterized by the dense gas fraction f dense) or the low star formation efficiency of dense gas (SFEdense). We find that SFEmol as traced by the CO emissions, when considering both star-forming and retired spaxels together, is tightly correlated with SFEdense and depends only weakly on f dense. The sSFR on kiloparsec scales is primarily driven by SFEmol and SFEdense, followed by the dependence on f mol, and is least correlated with f dense or the dense-gas-to-stellar mass ratio (R dense). When compared with other works in the literature, we find that our green valley sample shows lower global SFEmol and lower SFEdense while exhibiting similar dense gas fractions when compared to star-forming and starburst galaxies. We conclude that the star formation of the three green valley galaxies with a normal abundance of molecular gas is suppressed, mainly due to the reduced SFEdense rather than the lack of dense gas.

Keywords: galaxy evolution; green valley galaxies; molecular gas