adsabs/SciX_UAT_keywords huggingface dataset:
Plateau de Bure High-z Blue Sequence Survey 2 (PHIBSS2): Search for Secondary Sources, CO Luminosity Functions in the Field, and the Evolution of Molecular Gas Density through Cosmic Time

We report on the results of a search for serendipitous sources in CO emission in 110 cubes targeting CO(2 - 1), CO(3 - 2), and CO(6 - 5) at z ∼ 1-2 from the second Plateau de Bure High-z Blue Sequence Survey (PHIBSS2). The PHIBSS2 observations were part of a 4 yr legacy program at the IRAM Plateau de Bure Interferometer aimed at studying early galaxy evolution from the perspective of molecular gas reservoirs. We present a catalog of 67 candidate secondary sources from this search, with 45 of the 110 data cubes showing sources in addition to the primary target that appear to be field detections, unrelated to the central sources. This catalog includes redshifts, line widths, and fluxes, as well as an estimation of their reliability based on their false-positive probability. We perform a search in the 3D Hubble Space Telescope/CANDELS catalogs for the secondary CO detections and tentatively find that ∼64% of these have optical counterparts, which we use to constrain their redshifts. Finally, we use our catalog of candidate CO detections to derive the CO(2 - 1), CO(3 - 2), CO(4 - 3), CO(5 - 4), and CO(6 - 5) luminosity functions over a range of redshifts, as well as the molecular gas mass density evolution. Despite the different methodology, these results are in very good agreement with previous observational constraints derived from blind searches in deep fields. They provide an example of the type of "deep-field" science that can be carried out with targeted observations.

Keywords: galaxy evolution; luminosity function; high-redshift galaxies
One Hundred SMUDGes in S-PLUS: Ultra-diffuse Galaxies Flourish in the Field

We present the first systematic study of the stellar populations of ultra-diffuse galaxies (UDGs) in the field, integrating the large area search and characterization of UDGs by the SMUDGes survey with the twelve-band optical photometry of the S-PLUS survey. Based on Bayesian modeling of the optical colors of UDGs, we determine the ages, metallicities, and stellar masses of 100 UDGs distributed in an area of ∼330 deg2 in the Stripe 82 region. We find that the stellar masses and metallicities of field UDGs are similar to those observed in clusters and follow the trends previously defined in studies of dwarf and giant galaxies. However, field UDGs have younger luminosity-weighted ages than do UDGs in clusters. We interpret this result to mean that field UDGs have more extended star formation histories, including some that continue to form stars at low levels to the present time. Finally, we examine stellar population scaling relations that show that UDGs are, as a population, similar to other low surface brightness galaxies.

Keywords: low surface brightness galaxies; stellar populations; stellar ages; metallicity; stellar masses
Star Cluster Formation and Evolution in M101: An Investigation with the Legacy Extragalactic UV Survey

We present Hubble Space Telescope WFC3/UVIS (F275W, F336W) and ACS/WFC optical (F435W, F555W, and F814W) observations of the nearby grand-design spiral galaxy M101 as part of the Legacy Extragalactic UV Survey (LEGUS). Compact sources detected in at least four bands were classified by both human experts and the convolutional neural network STARCNET. Human experts classified the 2351 brightest sources, retrieving N c = 965 star clusters. STARCNET, trained on LEGUS data not including M101, classified all 4725 sources detected in four bands, retrieving N c = 2270 star clusters. The combined catalog represents the most complete census to date of compact star clusters in M101. We find that for the 2351 sources with both a visual- and machine-learning classification STARCNET is able to reproduce the human classifications at high levels of accuracy (~80%-90%), which is equivalent to the level of agreement between human classifiers in LEGUS. The derived cluster age distribution implies a disruption rate of ${dN}/d\tau \propto {\tau }^{-0.45\pm 0.14}$ over 107 < τ < 108.5 yr for cluster masses ≥103.55 M ⊙ for the central region of M101 and ${dN}/d\tau \propto {\tau }^{-0.02\pm 0.15}$ for cluster masses ≥103.38 M ⊙ in the northwest region of the galaxy. The trends we recover are weaker than those of other nearby spirals (e.g., M51) and starbursts, consistent with the M101 environment having a lower-density interstellar medium, and providing evidence in favor of environmentally dependent cluster disruption in the central, southeast, and northwest regions of M101.

Keywords: star clusters; star formation; spiral galaxies
Tracking of the C/2022 E3 (ZTF) from Trivandrum Observatory

Established in 1837, the Trivandrum observatory has been working over the past 185 yr as an institution catering to the scientific and academic community. After a major renovation recently, the arrival of the comet C/2022 E3 (ZTF) has provided an opportunity for the Trivandrum observatory to explore its capability in astronomy. The sky remained clear from February 13th onwards for 5 days, providing a much awaited window for tracking of the path of the comet. An apparent change in the coma is visualized in the images which could be associated with the increase in the radial distance from the Earth and also due to the increase in distance from the Sun.

Keywords: comets
Little Ado about Everything: ηCDM, a Cosmological Model with Fluctuation-driven Acceleration at Late Times

We propose a model of the Universe (dubbed ηCDM) featuring a controlled stochastic evolution of the cosmological quantities that is meant to render the effects of small deviations from homogeneity/isotropy on scales of 30-50 h -1 Mpc at late cosmic times associated with the emergence of the cosmic web. Specifically, we prescribe that the behavior of the matter/radiation energy densities in different patches of the Universe with such a size can be effectively described by a stochastic version of the mass-energy evolution equation. The latter includes, besides the usual dilution due to cosmic expansion, an appropriate noise term that statistically accounts for local fluctuations due to inhomogeneities, anisotropic stresses, and matter flows induced by complex gravitational processes. The evolution of the different patches as a function of cosmic time is rendered via the diverse realizations of the noise term; meanwhile, at any given cosmic time, sampling the ensemble of patches will create a nontrivial spatial distribution of the various cosmological quantities. Finally, the overall behavior of the Universe will be obtained by averaging over the patch ensemble. We assume a simple and physically reasonable parameterization of the noise term, gauging it against a wealth of cosmological data sets in the local and high-redshift Universe. We find that, with respect to standard ΛCDM, the ensemble-averaged cosmic dynamics in the ηCDM model is substantially altered by the stochasticity in three main respects: (i) an accelerated expansion is enforced at late cosmic times without the need for any additional exotic component (e.g., dark energy), (ii) the spatial curvature can stay small even in a low-density Universe constituted solely by matter and radiation, (iii) matter can acquire an effective negative pressure at late times. The ηCDM model is Hubble tension-free, meaning that the estimates of the Hubble constant from early- and late-time measurements do not show marked disagreement as in ΛCDM. We also provide specific predictions for the variance of the cosmological quantities among the different patches of the Universe at late cosmic times. Finally, the fate of the Universe in the ηCDM model is investigated to show that the cosmic coincidence problem is relieved without invoking the anthropic principle.

Keywords: cosmology; cosmological models; cosmological principle
3D Radiation-hydrodynamic Simulations Resolving Interior of Rapidly Accreting Primordial Protostar

Direct collapse of supermassive stars is a possible pathway to form supermassive black hole seeds at high redshifts. Whereas previous three-dimensional (3D) simulations demonstrate that supermassive stars form via rapid mass accretion, those resolving the stellar interior have been limited. Here, we report 3D radiation-hydrodynamic (RHD) simulations following the evolution of rapidly accreting protostars resolving the stellar interior. We use an adaptive mesh refinement code with our newly developed RHD solver employing an explicit M1 closure method. We follow the early evolution until the stellar mass reaches ~10 M ⊙ from two different initial configurations of spherical and turbulent clouds. We demonstrate that, in both cases, a swollen protostar whose radius is 100-1000 R ⊙ appears, as predicted by the stellar evolution calculations. Its effective temperature remains a few thousand Kelvin, and the radiative feedback by ionizing photons is too weak to disturb the accretion flow up to the epoch examined in this work. In the turbulent case, the protostar rotates rapidly at more than 0.4 times the Keplerian velocity owing to the angular momentum provided by the initial turbulence. The protostar approximates an oblate spheroid, and its equatorial radius is more than twice the polar radius. Our results suggest that we need to consider the rapid stellar rotation to elucidate the realistic 3D protostellar evolution in the supermassive star formation.

Keywords: star formation; early universe; supermassive black holes
Comet P/2021 HS (PANSTARRS) and the Challenge of Detecting Low-activity Comets

Jupiter-family comet (JFC) P/2021 HS (PANSTARRS) only exhibits a coma within a few weeks of its perihelion passage at 0.8 au, which is atypical for a comet. Here we present an investigation into the underlying cause using serendipitous survey detections and targeted observations. We find that the detection of the activity is caused by an extremely faint coma being enhanced by the forward scattering effect owing to the comet reaching a phase angle of ~140°. The coma morphology is consistent with sustained, sublimation-driven activity produced by a small active area, ~700 m2, one of the smallest values ever measured on a comet. The phase function of the nucleus shows a phase coefficient of 0.035 ± 0.002 mag deg-1, implying an absolute magnitude of H = 18.31 ± 0.04 and a phase slope of G = - 0.13, with color consistent with typical JFC nuclei. Thermal observations suggest a nucleus diameter of 0.6-1.1 km, implying an optical albedo of 0.04-0.23, which is higher than typical cometary nuclei. An unsuccessful search for dust trail and meteor activity confirms minimal dust deposit along the orbit, totaling ≲108 kg. As P/2021 HS is dynamically unstable, similar to typical JFCs, we speculate that it has an origin in the trans-Neptunian region and that its extreme depletion of volatiles is caused by a large number of previous passages to the inner solar system. The dramatic discovery of the cometary nature of P/2021 HS highlights the challenges of detecting comets with extremely low activity levels. Observations at high phase angle, where forward scattering is pronounced, will help identify such comets.

Keywords: comets; near-earth objects; short period comets; comae
CHIME Discovery of a Binary Pulsar with a Massive Nondegenerate Companion

Of the more than 3000 radio pulsars currently known, only ~300 are in binary systems, and only five of these consist of young pulsars with massive nondegenerate companions. We present the discovery and initial timing, accomplished using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope, of the sixth such binary pulsar, PSR J2108+4516, a 0.577 s radio pulsar in a 269 day orbit of eccentricity 0.09 with a companion of minimum mass 11 M ⊙. Notably, the pulsar undergoes periods of substantial eclipse, disappearing from the CHIME 400-800 MHz observing band for a large fraction of its orbit, and displays significant dispersion measure and scattering variations throughout its orbit, pointing to the possibility of a circumstellar disk or very dense stellar wind associated with the companion star. Subarcsecond resolution imaging with the Karl G. Jansky Very Large Array unambiguously demonstrates that the companion is a bright, V ≃ 11 OBe star, EM* UHA 138, located at a distance of 3.26(14) kpc. Archival optical observations of EM* UHA 138 approximately suggest a companion mass ranging from 17.5 M ⊙ < M c < 23 M ⊙, in turn constraining the orbital inclination angle to 50.°3 ≲ i ≲ 58.°3. With further multiwavelength follow-up, PSR J2108+4516 promises to serve as another rare laboratory for the exploration of companion winds, circumstellar disks, and short-term evolution through extended-body orbital dynamics.

Keywords: radio pulsars; binary pulsars; compact binary stars; pulsars; neutron stars; be stars; circumstellar disks
Differential Rotation of the Halo Traced by K-giant Stars

We use K-giant stars selected from the LAMOST DR5 to study the variation of the rotational velocity of the Galactic halo at different space positions. Modeling the rotational velocity distribution with both the halo and disk components, we find that the rotational velocity of the halo population decreases almost linearly with increasing vertical distance to the Galactic disk plane, Z, at fixed galactocentric radius, R. The samples are separated into two parts with $6\lt R\lt 12\,\mathrm{kpc}$ and $12\lt R\lt 20\,\mathrm{kpc}$ . We derive that the decreasing rates along Z for the two subsamples are -3.07 ± 0.63 and -1.89 ± 0.37 km s-1 kpc-1, respectively. Comparing with the TNG simulations, we suggest that this trend is caused by the interaction between the disk and halo. The results from the simulations show that only an oblate halo can provide a decreasing rotational velocity with increasing Z. This indicates that the Galactic halo is oblate with galactocentric radius $R\lt 20\,\mathrm{kpc}$ . On the other hand, the flaring of the disk component (mainly the thick disk) is clearly traced by this study; with R between 12 and 20 kpc, the disk can vertically extend to $6\sim 10\,\mathrm{kpc}$ above the disk plane. What is more interesting is that we find the Gaia-Enceladus-Sausage component has a significant contribution only in the halo with $R\lt 12\,\mathrm{kpc}$ , i.e., a fraction of 23%-47%, while in the outer subsample, the contribution is too low to be well constrained.

Keywords: milky way stellar halo; milky way galaxy; milky way rotation; milky way evolution; k giant stars; milky way dynamics; milky way disk
Evidence for an Interaction between the Galactic Center Clouds M0.10-0.08 and M0.11-0.11

We present high-resolution (~2-3″; ~0.1 pc) radio observations of the Galactic center cloud M0.10-0.08 using the Very Large Array at K and Ka band (~25 and 36 GHz). The M0.10-0.08 cloud is located in a complex environment near the Galactic center Radio Arc and the adjacent M0.11-0.11 molecular cloud. From our data, M0.10-0.08 appears to be a compact molecular cloud (~3 pc) that contains multiple compact molecular cores (5+; <0.4 pc). In this study, we detect a total of 15 molecular transitions in M0.10-0.08 from the following molecules: NH3, HC3N, CH3OH, HC5N, CH3CN, and OCS. We have identified more than sixty 36 GHz CH3OH masers in M0.10-0.08 with brightness temperatures above 400 K and 31 maser candidates with temperatures between 100 and 400 K. We conduct a kinematic analysis of the gas using NH3 and detect multiple velocity components toward this region of the Galactic center. The bulk of the gas in this region has a velocity of 51.5 km s-1 (M0.10-0.08) with a lower-velocity wing at 37.6 km s-1. We also detect a relatively faint velocity component at 10.6 km s-1 that we attribute to being an extension of the M0.11-0.11 cloud. Analysis of the gas kinematics, combined with past X-ray fluorescence observations, suggests M0.10-0.08 and M0.11-0.11 are located in the same vicinity of the Galactic center and could be physically interacting.

Keywords: galactic center; interstellar medium; molecular clouds
Haze Seasonal Variations of Titan's Upper Atmosphere during the Cassini Mission

This study presents a 13 yr survey of haze UV extinction profiles, monitoring the temporal evolution of the detached haze layer (DHL) in Titan's upper atmosphere (350-600 km). As reported by West et al. (GRL vol.38, L06204) at the equator, we show that the DHL was present at all latitudes below 55°N during the northern winter (2004-2009). Subsequently, it globally sunk and disappeared in 2012. No permanent DHL was observed between 2012 and 2015. Only in late 2015 did a new structure emerge from the Northern hemisphere, and propagate to the equator. This new DHL is not as pronounced as that observed in 2004, and is much more complex. In one specific sequence, in 2005, we were able to investigate the short timescale variability of the DHL, and no major changes were observed. When both sides of the limb were visible (dawn/dusk), we notice that the extinction of the DHL is slightly higher on the dawn side. Moreover, during a polar flyby in 2009, we observed the longitudinal variability of the DHL and spotted some local inhomogeneities. Finally, comparisons with UVIS stellar occultations and General Climate Models are both consistent with our findings. However, we noticed that the timing of the DHL main pattern predicted by the GMCs can be off by up to 30° in solar longitude. All these observations offer new perspectives on the seasonal cycle of Titan's upper atmosphere, the evolution of the DHL and its interaction with the dynamics.

Keywords: saturnian satellites; radiative transfer
Significant Molecular Gas Deficiencies in Star-forming Cluster Galaxies at z 1.4

We present the average gas properties derived from Atacama Large Millimeter Array (ALMA) Band 6 dust continuum imaging of 126 massive (log M ⋆/M ⊙ ≳ 10.5), star-forming cluster galaxies across 11 galaxy clusters at z = 1-1.75. Using stacking analysis on the ALMA images, combined with UV-far-infrared data, we quantify the average infrared spectral energy distributions (SEDs) and gas properties (molecular gas masses, M mol;gas depletion timescales, τ depl; and gas fractions, fgas) as functions of cluster-centric radius and properties including stellar mass and distance from the main sequence. We find a significant dearth in the ALMA fluxes relative to that expected in the field-with correspondingly low M mol and fgas, and short τ depl-with weak or no dependence on cluster-centric radius out to twice the virial radius. The Herschel+ALMA SEDs indicate warmer dust temperatures (~36-38 K) than coeval field galaxies (~30 K). We perform a thorough comparison of the cluster galaxy gas properties to field galaxies, finding deficits of 2-3×, 3-4×, and 2-4× in M mol, τ depl, and fgas compared to coeval field stacks, and larger deficits compared to field scaling relations built primarily on detections. The cluster gas properties derived here are comparable with stacking analyses of (proto-)clusters in the literature, and at odds with findings of field-like τ depl and enhanced fgas reported using CO and dust continuum detections. Our analysis suggests that environment has a considerable impact on gas properties out to large radii, in good agreement with cosmological simulations which project that gas depletion begins beyond the virial radius and largely completes by first passage of the cluster core.

Keywords: galactic and extragalactic astronomy; galaxy clusters; high-redshift galaxy clusters; molecular gas; galaxy quenching
A Machine Learning-Based Approach to Time-series Wave Identification in the Solar Wind

The Wind spacecraft has yielded several decades of high-resolution magnetic field data, a large fraction of which displays small-scale structures. In particular, the solar wind is full of wavelike fluctuations that appear in both the field magnitude and its components. The nature of these fluctuations can be tied to the properties of other structures in the solar wind, such as shocks, that have implications for the time evolution of the solar wind. As such, having a large collection of wave events would facilitate further study of the effects that these fluctuations have on solar wind evolution. Given the large volume of magnetic field data available, machine learning is the most practical approach to classifying the myriad small-scale structures observed. To this end, a subset of Wind data is labeled and used as a training set for a multibranch 1D convolutional neural network aimed at classifying circularly polarized wave modes. Using this algorithm, a preliminary statistical study of 1 yr of data is performed, yielding about 300,000 wave intervals out of about 5,000,000 solar wind intervals. The wave intervals come about more often in the fast solar wind and at higher temperatures, and the number of waves per day is highly periodic. This machine learning-based approach to wave detection has the potential to be a powerful, inexpensive way to catalog waves throughout decades of spacecraft data.

Keywords: solar wind; interplanetary physics; space weather; space plasmas; neural networks; convolutional neural networks; alfven waves
Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97-1.32 μm

Stellar absorption lines of heavy elements can give us various insights into the chemical evolution of our Galaxy and other nearby galaxies. Recently developed spectrographs for the near-infrared wavelengths are becoming more and more powerful at producing a large number of high-quality spectra, but identification and characterization of the absorption lines in the infrared range remain to be fulfilled. We searched for lines of elements heavier than the iron group, I.e., those heavier than Ni, in the Y (9760-11100 Å) and J (11600-13200 Å) bands. We considered the lines in three catalogs, I.e., the Vienna Atomic Line Database, the compilation by R. Kurucz, and the list published in 1999 by Meléndez & Barbuy. Candidate lines were selected based on synthetic spectra, and the confirmation was done by using WINERED spectra of 13 giants and supergiants within FGK spectral types (spanning 4000-7200 K in the effective temperature). We have detected lines of Zn I, Sr II, Y II, Zr I, Ba II, Sm II, Eu II, and Dy II, in the order of atomic number. Although the number of the lines is small, 23 in total, they are potentially useful diagnostic lines of the Galactic chemical evolution, especially in those regions for which interstellar extinction hampers detailed chemical analyses with spectra in shorter wavelengths. We also report the detection of lines whose presence was not predicted by the synthetic spectra created with the above three line lists.

Keywords: spectroscopy; high resolution spectroscopy; spectral line identification; spectral line lists; stellar spectral lines; late-type giant stars; late-type supergiant stars; late-type dwarf stars; near infrared astronomy
Searching the Entirety of Kepler Data. I. 17 New Planet Candidates Including One Habitable Zone World

We present the results of an independent search of all ∼200,000 stars observed over the four year Kepler mission (Q1-Q17) for multiplanet systems, using a three-transit minimum detection criterion to search orbital periods up to hundreds of days. We incorporate both automated and manual triage, and provide estimates of the completeness and reliability of our vetting pipeline. Our search returned 17 planet candidates (PCs) in addition to thousands of known Kepler Objects of Interest (KOIs), with a 98.8% recovery rate of already confirmed planets. We highlight the discovery of one candidate, KIC-7340288 b, that is both rocky (radius $\leqslant 1.6{R}_{\oplus }$ ) and in the Habitable Zone (insolation between 0.25 and 2.2 times the Earth's insolation). Another candidate is an addition to the already known KOI-4509 system. We also present adaptive optics imaging follow-up for six of our new PCs, two of which reveal a line-of-sight stellar companion within 4″.

Keywords: exoplanets; exoplanet detection methods; transit photometry; exoplanet systems; habitable planets