Sazuna/UAT_keywords huggingface dataset:
The Multilayer Nature of Molecular Gas toward the Cygnus Region. We study the physical properties and 3D distribution of molecular clouds (MCs) toward the Cygnus region using the MWISP CO survey and Gaia DR3 data. Based on Gaussian decomposition and clustering for 13CO lines, over 70% of the fluxes are recovered. With the identification result of 13CO structures, two models are designed to measure the distances of the molecular gas in velocity crowding regions. The distances of more than 200 large 13CO structures are obtained toward the 150 deg2 region. Additionally, tens of the identified MC structures coincide well with masers and/or intense mid-IR emission. We find multiple gas layers toward the region: (1) the extensive gas structures composing the Cygnus Rift from 700 pc to 1 kpc across the whole region; (2) the ∼1.3 kpc gas layer mainly in the Cygnus X South region; and (3) the 1.5 kpc dense filament at the Cygnus X North region and many cometary clouds shaped by Cygnus OB2. We also note that the spatial distribution of young stellar object candidates is generally consistent with the molecular gas structures. The total molecular mass of the Cygnus region is estimated to be ∼2.7 × 106 M ⊙ assuming an X-factor ratio ${X}_{\mathrm{CO}}=2\times {10}^{20}\,{\mathrm{cm}}^{-2}{\,({\rm{K}}\,\mathrm{km}\,{{\rm{s}}}^{-1})}^{-1}$ . The foreground Cygnus Rift contributes ∼25% of the molecular mass in the whole region. Our work presents a new 3D view of the MCs' distribution toward the Cygnus X region, as well as the exact molecular gas mass distribution in the foreground Cygnus Rift.

Keywords: Molecular gas, Distance measure, Molecular clouds, Interstellar medium
The Emerging Stellar Complex in Mon R2: Membership and Optical Variability Classification. Monoceros R2 (Mon R2) is one of the closest large active star-forming regions. This extremely young and partially embedded region provides an excellent laboratory for studying star formation and the early evolution of young stellar objects (YSOs). In this paper, we conduct an optical study of the greater Mon R2 region. Beginning with 1690 previously identified candidate YSOs, we used 496 sources with good proper motions and parallaxes from Gaia Data Release (DR) 3 to determine the astrometric properties for likely members of Mon R2. We then used both astrometric and photometric (isochronal and variability) criteria to determine that 308 of these stars are highly probable members. Using the same criteria, we considered a broad area search around Mon R2 in Gaia DR3 and separated candidate members from field stars. In total, we selected 651 likely new cluster members that had been missed in the previous X-ray and infrared excess selection techniques used in the past to establish cluster membership. Revised astrometric properties of the cluster were found using the combined sample of ∼959 highly probable member stars. For the literature plus the new candidate member list, optical light curves were compiled from the Zwicky Transient Facility. For 470 identified variable sources, we attempted classification based on the flux asymmetry (M) and quasiperiodicity (Q) metrics. We find that Mon R2 is dominated by quasiperiodic symmetric variables, with aperiodic sources also a significant population. A few tens of large-amplitude variables are identified that may be of interest for further study.

Keywords: Star forming regions, T Tauri stars, Young stellar objects, Pre-main sequence stars, Variable stars, Stellar associations
Hyper Illumination of Exoplanets: Analytical and Numerical Approaches. This work describes the illumination of exoplanets whose orbits are close enough to their host star that the finite angular size of their host star causes hyper illumination, in which more than 50% of the planet receives light. Such exoplanets include the hot Jupiters KELT-9 b (64.5% illuminated) and Kepler-91 b (69.6% illuminated). We describe the geometry of three primary illumination zones: the fully illuminated zone, penumbral zone, and unilluminated zone. The integrals required to determine the incident radiation as a function of position from the substellar point on the exoplanet are explained and derived, and the analytical solution is presented within the fully illuminated zone. We find that the illumination predicted by our model is greater at the substellar point than the typical plane-parallel ray model used would suggest. In addition, it is greater within the region of the penumbral zone extending into the antistellar side of the exoplanet. Finally, we compare our model to that used in starry, an open-source software package used to create albedo maps. It appears that starry may be overestimating the illumination of closely orbiting exoplanets because the foreshortening of the area element of the host star is not included in its calculation.

Keywords: Analytical mathematics, Exoplanets
Modeling JWST MIRI-MRS Observations of T Cha: Mid-IR Noble Gas Emission Tracing a Dense Disk Wind. [Ne II] 12.81 μm emission is a well-used tracer of protoplanetary disk winds due to its blueshifted line profile. Mid-Infrared Instrument (MIRI)-Medium Resolution Spectrometer (MRS) recently observed T Cha, detecting this line along with lines of [Ne III], [Ar II], and [Ar III], with the [Ne II] and [Ne III] lines found to be extended while the [Ar II] was not. In this complementary work, we use these lines to address long-debated questions about protoplanetary disk winds regarding their mass-loss rate, the origin of their ionization, and the role of magnetically driven winds as opposed to photoevaporation. To this end, we perform photoionization radiative transfer on simple hydrodynamic wind models to map the line emission. We compare the integrated model luminosities to those observed with MIRI-MRS to identify which models most closely reproduce the data and produce synthetic images from these to understand what information is captured by measurements of the line extents. Along with the low degree of ionization implied by the line ratios, the relative compactness of [Ar II] compared to [Ne II] is particularly constraining. This requires Ne II production by hard X-rays and Ar II production by soft X-rays (and/or EUV) in an extended (≳10 au) wind that is shielded from soft X-rays, necessitating a dense wind with material launched on scales down to ∼1 au. Such conditions could be produced by photoevaporation, whereas an extended magnetohydrodynamic (MHD) wind producing equal shielding would likely underpredict the line fluxes. However, a tenuous inner MHD wind may still contribute to shielding the extended wind. This picture is consistent with constraints from spectrally resolved line profiles.

Keywords: Radiative transfer simulations, Photoionization, Protoplanetary disks, Infrared spectroscopy
Candidate Main-belt Asteroids for Surface Heterogeneity. Large terrestrial bodies in our solar system like the Earth, Mars, Mercury, and the Moon exhibit geologically complex surfaces with compositional heterogeneity. From past studies using large telescopes and spacecraft, it was shown that asteroids with diameters larger than 100 km also show surface heterogeneity at hemispheric scales, while on smaller objects, such features remain to be detected. Here, we investigate candidates for surface heterogeneity in a sample of 130 main-belt asteroids using multiepoch spectroscopic data from the MIT–Hawaii Near-Earth Object Spectroscopic Survey, which has been observing asteroids for about 20 yr using a self-consistent observation technique. Twelve conservative candidates with spectra more than 3σ apart from each other at 2.4 μm and 52 optimistic candidates for surface heterogeneity are detected. These candidates include eight objects already reported as being heterogeneous. Our study suggests that the size boundary between small homogeneous asteroids and larger heterogeneous objects, if it exists, is lower than 100 km. A-type asteroids have a higher proportion of heterogeneous candidates than other asteroids. This may be because olivine, which is the main surface constituent of these objects, reacts more efficiently to space weathering with respect to pyroxene, such that a similar range of surface ages will translate into a wider range of optical-to-near-infrared spectral slopes in the case of A-type bodies.

Keywords: Main belt asteroids, Asteroids, Small Solar System bodies, Asteroid surfaces
Verification of Hypervelocity Bulge Red Clump Stars. We verify candidate hypervelocity red clump stars located in the Galactic bulge that were selected based on the VVV and the Gaia DR2 data by Luna et al. To do so, we analyze data from the OGLE-IV survey: difference images and astrometric time series. We have data for 30 stars out of 34 hypervelocity candidates. We confirmed the high proper motion of only one of these stars and find out that it is a nearby one, hence, not a hypervelocity star. To sum up, we do not confirm the candidate stars as hypervelocity ones. Hence, we disprove the production rate of hypervelocity red clump stars by the central supermassive black hole provided by Luna et al.

Keywords: Galaxy dynamics, Hypervelocity stars, Proper motions
Prototype Faraday Rotation Measure Catalogs from the Polarisation Sky Survey of the Universe's Magnetism (POSSUM) Pilot Observations. The Polarisation Sky Survey of the Universe's Magnetism (POSSUM) will conduct a sensitive ∼1 GHz radio polarization survey covering 20,000 deg2 of the southern sky with the Australian Square Kilometre Array Pathfinder. In anticipation of the full survey, we analyze pilot observations of low-band (800─1087 MHz), mid-band (1316─1439 MHz), and combined-band observations for an extragalactic field and a Galactic plane field (low-band only). Using the POSSUM processing pipeline, we produce prototype rotation measure (RM) catalogs that are filtered to construct prototype RM grids. We assess typical RM grid densities and RM uncertainties and their dependence on frequency, bandwidth, and Galactic latitude. We present a median filter method for separating foreground diffuse emission from background components and find that after application of the filter, 99.5% of the measured RMs of simulated sources are within 3σ of their true RM, with a typical loss of polarized intensity of 5% ± 5%. We find RM grid densities of 35.1, 30.6, 37.2, and 13.5 RMs per square degree and median uncertainties on RM measurements of 1.55, 12.82, 1.06, and 1.89 rad m−2 for the median-filtered low-band, mid-band, combined-band, and Galactic observations, respectively. We estimate that the full POSSUM survey will produce an RM catalog of ∼775,000 RMs with median-filtered low-band observations and ∼877,000 RMs with median-filtered combined-band observations. We construct a structure function from the Galactic RM catalog, which shows a break at 0.°7, corresponding to a physical scale of 12─24 pc for the nearest spiral arm.

Keywords: Galaxy magnetic fields, Spectropolarimetry, Sky surveys, Astrophysical magnetism, Polarimetry, Catalogs, Extragalactic magnetic fields
Asteroseismological Analysis of the Non-Blazhko RRab Star EPIC 248846335 in the LAMOST–Kepler/K2 Project. We conduct an asteroseismological analysis on the non-Blazhko ab-type RR Lyrae star EPIC 248846335, employing the Radial Stellar Pulsations module of the Modules for Experiments in Stellar Astrophysics based on the set of stellar parameters. The atmospheric parameters T eff = 6933 ± 70 K, log g = 3.35 ± 0.50, and [Fe/H] = ‑1.18 ± 0.14 are estimated from low-resolution spectra of LAMOST DR9. The luminosity L =   ${49.70}_{-1.80}^{+2.99}$   L ⊙ and mass M = 0.56 ± 0.07 M ⊙ are calculated, respectively, using the distance provided by Gaia and the metallicity estimated from the low-resolution spectra. The Fourier parameters of the light curves observed by K2 and radial velocity (RV) curves determined from the medium-resolution spectra of LAMOST DR10 are also calculated in this work. The period of the fundamental mode of the star and the residuals r of the Fourier parameters between the models and observations serve to select an optimal model, whose stellar parameters are T eff = 6700 ± 220 K, log g = 2.70, [Fe/H] = ‑1.20 ± 0.2, M = 0.59 ± 0.05 M ⊙, and L = 56.0 ± 4.2 L ⊙. The projection factors are constrained as 1.20 ± 0.02 and 1.59 ± 0.13 by the blue- and red-arm observed velocities with their corresponding RV curves derived from the best-fit model, respectively. The precise determination of stellar parameters in ab-type RR Lyrae stars is crucial for understanding the physical processes that occur during pulsation and for providing a deeper understanding of their period–luminosity relationship.

Keywords: RRab variable stars, RR Lyrae variable stars
Implication of the Velocity Dispersion Scalings on High-mass Star Formation in Molecular Clouds. This paper is aimed at exploring the implications of velocity-dispersion scalings on high-mass star formation in molecular clouds, including the scalings of Larson's linewidth─size (σ─ R) and ratio─mass surface density ( ${ \mathcal L }$ ─ Σ; here ${ \mathcal L }$ = σ/R 0.5). We have systematically analyzed the σ parameter of well-selected 221 massive clumps, complemented with published samples of other hierarchical density structures of molecular clouds over spatial scales of 0.01─10 pc. Those massive clumps are classified into four phases: quiescent, protostellar, H II region, and PDR clumps in an evolutionary sequence. The velocity dispersion of clumps increases overall with the evolutionary sequence, reflecting enhanced stellar feedback in more evolved phases. The relations of σ─ R and ${ \mathcal L }$ ─ Σ are weak with the clump sample alone, but become evident when combined with others spanning a much wider spatial scales. For σ─ R, its tight relation indicates a kinematic connection between hierarchical density structures, supporting theoretical models of multiscale high-mass star formation. From the ${ \mathcal L }$ ─ Σ relation, cloud structures can be found to transition from overvirial state (α vir &gt; 2) to subvirial state (α vir &lt; 2) as they become smaller and denser, indicating a possible shift in the governing force from turbulence to gravity. This implies that the multiscale physical process of high-mass star formation hinges on the self-gravity of subvirial molecular clouds. However, the influence of turbulence may not be dismissed until large-scale clouds attain a subvirial state. This is pending confirmation from future multiscale kinematic observations of molecular clouds with uniform observing settings.

Keywords: Star formation, Interstellar dynamics, Interstellar medium
How Well is the International Celestial Reference System Maintained in Official IAU Implementations?. The International Celestial Reference Frame (ICRF) based on the VLBI-derived positions of 608 extragalactic radio sources was adopted by the International Astronomical Union (IAU) in 1998 as the first realization of the International Celestial Reference System (ICRS). Later, in 2009 and 2020, two extended ICRF versions, ICRF2 and ICRF3, respectively, were released. The latter is adopted by the IAU as the current implementation of the ICRF in the radio band. In the meantime, the Gaia mission delivered three versions of the optical ICRS realization in 2016, 2018, and 2022 with an accuracy similar to that achieved by VLBI-based ICRF. The Gaia-CRF catalogs were linked to the ICRF under no-rotation conditions and thus may suffer from ICRF systematic instability if the latter is substantial. In this work, a new analysis was performed to assess the long-term stability of radio and optical ICRS realizations. Based on the 16-parameter vector spherical harmonics expansion of the differences between the three ICRF catalogs, it can be concluded that the mutual orientation between them is at a level of a few tens of microarcseconds, while the components of the glide vector and E 2,0 term are several times greater. A comparison of the three Gaia-CRF catalogs with the ICRF3-SX showed that for the latest Gaia-CRF catalog, Gaia-CRF3, all rotational and deformation components are below 20 μas except for the E 2,0 term, which is several times greater. For both ICRF and Gaia-CRF catalogs, the evolution of the source position errors is also tracked.

Keywords: Astronomical coordinate systems, Radio source catalogs, Very long baseline interferometry, Astrometry, Gaia
Is the RSGC4 (Alicante 8) Cluster a Real Star Cluster? Peculiar Radial Velocities of Red Supergiant Stars. Young massive star clusters, like the six red supergiant clusters in the Scutum complex, provide valuable insights into star formation and galaxy structures. We investigated the high-resolution near-infrared spectra of 60 RSG candidates in these clusters using the Immersion Grating Infrared Spectrograph. Among the candidates in RSGC4, we found significant scattering in radial velocity (−64 to 115 km s−1), unlike other clusters with velocities of ∼100 km s−1. Most candidates in RSGC4 have Q  GK  s   values larger than 1.7, suggesting that they could be early AGB stars. Four candidates in RSGC4 exhibit infrared excess and distinct absorption features absent in other candidates. Two of these stars exhibit absorption lines resembling those of D-type symbiotic stars, showing radial velocity changes in multiepoch observations. Analysis of relative proper motions revealed no runaway/walkaway stars in RSGC4. The dynamic properties of RSGC4 and RSGC1 differ from the disklike motions of other clusters: RSGC4 has low normalized horizontal action J hor = J  ϕ /J tot and vertical action J ver = (J z − J R)/J tot values and high eccentricities, while RSGC1 has vertical motions with high J ver values and inclinations. We propose that RSGC4 may not be a genuine star cluster but rather a composite of RSGs and AGB stars distributed along the line of sight at similar distances, possibly originating from various environments. Our results suggest a complex and hierarchical secular evolution of star clusters in the Scutum complex, emphasizing the importance of considering factors beyond density crowding when identifying star clusters in the bulge regions.

Keywords: High resolution spectroscopy, Red supergiant stars, Young massive clusters, Star clusters, Near infrared astronomy
Differencing and Coadding JWST Images with Matched Point-spread Function. We present an algorithm to derive difference images for data taken with JWST with matched point-spread functions (PSFs). It is based on the saccadic fast Fourier transform method but with revisions to accommodate the rotations and spatial variations of the PSFs. It allows for spatially varying kernels in B-spline form with separately controlled photometric scaling and Tikhonov kernel regularization for harnessing the ultimate fitting flexibility. We present this method using the JWST/NIRCam images of galaxy cluster Abell 2744 acquired in JWST Cycle 1 as the test data. The algorithm can be useful for time-domain source detection and differential photometry with JWST. It can also coadd images of multiple exposures taken at different field orientations. The coadded images preserve the sharpness of the central cores of the PSFs, and the positions and shapes of the objects are matched precisely with B-splines across the field.

Keywords: Transient detection, Astronomy software
Sites of Planet Formation in Binary Systems. I. Evidence for Disk‑Orbit Alignment in the Close Binary FO Tau. Close binary systems present challenges to planet formation. As binary separations decrease, so do the occurrence rates of protoplanetary disks in young systems and planets in mature systems. For systems that do retain disks, their disk masses and sizes are altered by the presence of the binary companion. Through the study of protoplanetary disks in binary systems with known orbital parameters, we seek to determine the properties that promote disk retention and therefore planet formation. In this work, we characterize the young binary‑disk system FO Tau. We determine the first full orbital solution for the system, finding masses of   ${0.35}_{-0.05}^{+0.06}\ {M}_{\odot }$   and 0.34 ± 0.05 M ⊙ for the stellar components, a semimajor axis of   $22{\,(}_{-1}^{+2})$   au, and an eccentricity of   $0.21{\,(}_{-0.03}^{+0.04})$  . With long-baseline Atacama Large Millimeter/submillimeter Array interferometry, we detect 1.3 mm continuum and 12CO (J = 2–1) line emission toward each of the binary components; no circumbinary emission is detected. The protoplanetary disks are compact, consistent with being truncated by the binary orbit. The dust disks are unresolved in the image plane, and the more extended gas disks are only marginally resolved. Fitting the continuum and CO visibilities, we determine the inclination of each disk, finding evidence for alignment of the disk and binary orbital planes. This study is the first of its kind linking the properties of circumstellar protoplanetary disks to a precisely known binary orbit. In the case of FO Tau, we find a dynamically placid environment (coplanar, low eccentricity), which may foster its potential for planet formation.

Keywords: Close binary stars, Young stellar objects, Binary stars, Protoplanetary disks
Identification of the Top TESS Objects of Interest for Atmospheric Characterization of Transiting Exoplanets with JWST. JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates are still unconfirmed and many of the best planets for atmospheric characterization may remain to be identified. We present a sample of TESS planets and planet candidates that we identify as "best-in-class" for transmission and emission spectroscopy with JWST. These targets are sorted into bins across equilibrium temperature T eq and planetary radius R p and are ranked by a transmission and an emission spectroscopy metric (TSM and ESM, respectively) within each bin. We perform cuts for expected signal size and stellar brightness to remove suboptimal targets for JWST. Of the 194 targets in the resulting sample, 103 are unconfirmed TESS planet candidates, also known as TESS Objects of Interest (TOIs). We perform vetting and statistical validation analyses on these 103 targets to determine which are likely planets and which are likely false positives, incorporating ground-based follow-up from the TESS Follow-up Observation Program to aid the vetting and validation process. We statistically validate 18 TOIs, marginally validate 31 TOIs to varying levels of confidence, deem 29 TOIs likely false positives, and leave the dispositions for four TOIs as inconclusive. Twenty-one of the 103 TOIs were confirmed independently over the course of our analysis. We intend for this work to serve as a community resource and motivate formal confirmation and mass measurements of each validated planet. We encourage more detailed analysis of individual targets by the community.

Keywords: Exoplanets, Exoplanet astronomy, James Webb Space Telescope, Transit photometry, Exoplanet atmospheres