adsabs/SciX_UAT_keywords huggingface dataset:
UCLCHEMCMC: An MCMC Inference Tool for Physical Parameters of Molecular Clouds

We present the publicly available open-source code UCLCHEMCMC, designed to estimate physical parameters of an observed cloud of gas by combining Markov chain Monte Carlo (MCMC) sampling with chemical and radiative transfer modeling. When given the observed values of different emission lines, UCLCHEMCMC runs a Bayesian parameter inference, using an MCMC algorithm to sample the likelihood and produce an estimate of the posterior probability distribution of the parameters. UCLCHEMCMC takes a full forward-modeling approach, generating model observables from the physical parameters via chemical and radiative transfer modeling. While running UCLCHEMCMC, the created chemical models and radiative transfer code results are stored in an SQL database, preventing redundant model calculations in future inferences. This means that the more UCLCHEMCMC is used, the more efficient it becomes. Using UCLCHEM and RADEX, the increase oin efficiency is nearly two orders of magnitude, going from 5185.33 ± 1041.96 s for 10 walkers to take 1000 steps when the database is empty, to 68.89 ± 45.39 s when nearly all models requested are in the database. In order to demonstrate its usefulness, we provide an example inference of UCLCHEMCMC to estimate the physical parameters of mock data, and perform two inferences on the well-studied prestellar core, L1544, one of which shows that it is important to consider the substructures of an object when determining which emission lines to use.

Keywords: astrochemistry; interdisciplinary astronomy; markov chain monte carlo; bayesian statistics; posterior distribution
Data Combination: Interferometry and Single-dish Imaging in Radio Astronomy

Modern interferometers routinely provide radio-astronomical images down to subarcsecond resolution. However, interferometers filter out spatial scales larger than those sampled by the shortest baselines, which affects the measurement of both spatial and spectral features. Complementary single-dish data are vital for recovering the true flux distribution of spatially resolved astronomical sources with such extended emission. In this work, we provide an overview of the prominent available methods to combine single-dish and interferometric observations. We test each of these methods in the framework of the CASA data analysis software package on both synthetic continuum and observed spectral data sets. We develop a set of new assessment tools that are generally applicable to all radio-astronomical cases of data combination. Applying these new assessment diagnostics, we evaluate the methods' performance and demonstrate the significant improvement of the combined results in comparison to purely interferometric reductions. We provide combination and assessment scripts as add-on material. Our results highlight the advantage of using data combination to ensure high-quality science images of spatially resolved objects.

Keywords: millimeter astronomy; submillimeter astronomy; interferometry; fast fourier transform; spectroscopy; astronomical techniques
Characterizing a World Within the Hot-Neptune Desert: Transit Observations of LTT 9779 b with the Hubble Space Telescope/WFC3

We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot-Neptune desert, that has been observed with Hubble Space Telescope (HST)/WFC3 with G102 and G141. The combined transmission spectrum, which covers 0.8-1.6 μm, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H2O, CO2, and FeH with a significance of 3.1σ, 2.4σ, and 2.1σ, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 μm helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which are not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyα.

Keywords: exoplanets; hot neptunes; infrared spectroscopy; hubble space telescope
Molecular Gas Structures Traced by 13CO Emission in the 18,190 12CO Molecular Clouds from the MWISP Survey

After morphological classification of 18,190 12CO molecular clouds, we further investigate the properties of their internal molecular gas structures traced by the 13CO (J = 1-0) line emissions. Using three different methods to extract the 13CO gas structures within each 12CO cloud, we find that ~15% of the 12CO clouds (2851) have 13CO gas structures and these 12CO clouds contribute about 93% of the total integrated flux of 12CO emission. In each of the 2851 12CO clouds with 13CO gas structures, the 13CO emission area generally does not exceed 70% of the 12CO emission area, and the 13CO integrated flux does not exceed 20% of the 12CO integrated flux. We reveal a strong correlation between the velocity-integrated intensities of 12CO lines and those of 13CO lines in both 12CO and 13CO emission regions. This indicates the H2 column densities of molecular clouds are crucial for the 13CO line emission. After linking the 13CO structure detection rates of the 18,190 12CO molecular clouds to their morphologies, i.e., nonfilaments and filaments, we find that the 13CO gas structures are primarily detected in 12CO clouds with filamentary morphologies. Moreover, these filaments tend to harbor more than one 13CO structure. That demonstrates filaments not only have larger spatial scales, but also have more molecular gas structures traced by 13CO lines, i.e., local gas density enhancements. Our results favor the turbulent compression scenario for filament formation, in which dynamical compression of turbulent flows induces local density enhancements. The nonfilaments tend to be in the low-pressure and quiescent turbulent environments of the diffuse interstellar medium.

Keywords: interstellar medium; interstellar molecules; molecular clouds
Radiation Hydrodynamics of Turbulent H II Regions in Molecular Clouds: A Physical Origin of LyC Leakage and the Associated Lyα Spectra

We examine Lyman continuum (LyC) leakage through H II regions regulated by turbulence and radiative feedback in a giant molecular cloud in the context of fully coupled radiation hydrodynamics (RHD). The physical relations of the LyC escape with H I covering fraction, kinematics, ionizing photon production efficiency, and emergent Lyα line profiles are studied using a series of RHD turbulence simulations performed with RAMSES-RT. The turbulence-regulated mechanism allows ionizing photons to leak out at early times before the onset of supernova feedback. The LyC photons escape through turbulence-generated low column density channels that are evacuated efficiently by radiative feedback via photoheating-induced shocks across the D-type ionization fronts. The Lyα photons funnel through the photoionized channels along the paths of LyC escape, resulting in a diverse Lyα spectral morphology including narrow double-peaked profiles. The Lyα peak separation is controlled by the residual H I column density of the channels, and the line asymmetry correlates with the porosity and multiphase structure of the H II region. This mechanism through the turbulent H II regions can naturally reproduce the observed Lyα spectral characteristics of some of the LyC-leaking galaxies. This RHD turbulence origin provides an appealing hypothesis to explain high LyC leakage from very young (∼3 Myr) star-forming galaxies found in the local universe without need of extreme galactic outflows or supernova feedback. We discuss the implications of the turbulent H II regions on other nebular emission lines and a possible observational test with the Magellanic System and local blue compact dwarf galaxies as analogs of reionization-era systems.

Keywords: reionization; h ii regions; hydrodynamics; radiative transfer
Electrostatic Wave Decay in the Randomly Inhomogeneous Solar Wind

Despite a few space observations where Langmuir and ion acoustic waves are expected to participate in the mechanism of electrostatic decay, this is to date believed to be the main and fastest nonlinear wave process in the solar wind. However, in such a plasma where random density fluctuations are ubiquitous, the question of whether nonlinear wave processes play a significant role in Langmuir wave turbulence generated by electron beams associated with type III solar radio bursts remains still open. This paper provides several answers by studying, owing to two-dimensional challenging particle-in-cell simulations, the dynamics and the properties of the ion acoustic waves excited by such Langmuir wave turbulence and the role they play in the electrostatic decay. The impact on this process of plasma background density fluctuations and electron-to-ion temperature ratio is studied. Moreover, it is shown that, for a typical solar wind plasma with an average level of density fluctuations of a few percent of the ambient density and a temperature ratio of the order of 1, nonlinear induced scattering off ions occurs, with small intensity low-frequency quasi-modes and only in localized plasma regions where density is depleted or weakly perturbed by low-frequency turbulence.

Keywords: solar electromagnetic emission; solar wind; radio bursts; solar flares
Census of High- and Medium-mass Protostars. V. CO Abundance and the Galactic XCO Factor

We present the second dust continuum data release in the Census of High- and Medium-mass Protostars (CHaMP), expanding the methodology trialed in Pitts et al. to the entire CHaMP survey area (280° < ℓ < 300°, - 4° < b < + 2°). This release includes maps of dust temperature (Td), H2 column density ( ${N}_{{{\rm{H}}}_{2}}$ ), gas-phase CO abundance, and temperature-density plots for every prestellar clump with Herschel coverage, showing no evidence of internal heating for most clumps in our sample. We show that CO abundance is a strong function of Td and can be fit with a second-order polynomial in log-space, with a typical dispersion of a factor of 2-3. The CO abundance peaks at ${20.0}_{-1.0}^{+0.4}$ K with a value of ${7.4}_{-0.3}^{+0.2}\times {10}^{-5}$ per H2; the low Td at which this maximal abundance occurs relative to laboratory results is likely due to interstellar UV bombardment in the largest survey fields. Finally, we show that, as predicted by theoretical literature and hinted at in previous studies of individual clouds, the conversion factor from integrated 12CO line intensity ( ${I}_{{}^{12}{\rm{CO}}}$ ) to ${N}_{{{\rm{H}}}_{2}}$ , the XCO factor, varies as a broken power law in ${I}_{{}^{12}{\rm{CO}}}$ with a transition zone between 70 and 90 K km s-1. The XCO function we propose has ${N}_{{{\rm{H}}}_{2}}\propto {I}_{{}^{12}{\rm{CO}}}^{0.51}$ for ${I}_{{}^{12}{\rm{CO}}}\lesssim 70$ K km s-1 and ${N}_{{{\rm{H}}}_{2}}\propto {I}_{{}^{12}{\rm{CO}}}^{2.3}$ for ${I}_{{}^{12}{\rm{CO}}}\gtrsim 90$ K km s-1. The high- ${I}_{{}^{12}{\rm{CO}}}$ side should be generalizable with known adjustments for metallicity, but the influence of interstellar UV fields on the low- ${I}_{{}^{12}{\rm{CO}}}$ side may be sample specific. We discuss how these results expand on previous works in the CHaMP series and help tie together observational, theoretical, and laboratory studies on CO over the past decade.

Keywords: dust continuum emission; co line emission; interstellar medium; milky way disk; protostars; young stellar objects; circumstellar dust; circumstellar matter; star formation
NuSTAR Non-detection of a Faint Active Galactic Nucleus in an Ultraluminous Infrared Galaxy with Kpc-scale Fast Wind

Large-scale outflows are generally considered to be possible evidence that active galactic nuclei (AGNs) can severely affect their host galaxies. Recently, an ultraluminous infrared galaxy (ULIRG) at z = 0.49, AKARI J0916248+073034, was found to have a galaxy-scale [O III] λ5007 outflow with one of the highest energy-ejection rates at z < 1.6. However, the central AGN activity estimated from its torus mid-infrared (MIR) radiation is weak relative to the luminous [O III] emission. In this work we report the first NuSTAR hard X-ray follow-up of this ULIRG to constrain its current AGN luminosity. The intrinsic 2-10 keV luminosity shows a 90% upper limit of 3.0 × 1043 erg s-1 assuming Compton-thick obscuration (NH = 1.5 × 1024 cm-2), which is only 3.6% of the luminosity expected from the extinction-corrected [O III] luminosity. Using the NuSTAR observation, we successfully identify that this ULIRG has a very extreme case of X-ray deficit among local ULIRGs. A possible scenario to explain the drastic decline in both the corona (X-ray) and torus (MIR) is that the primary radiation from the AGN accretion disk is currently in a fading status, as a consequence of a powerful nuclear wind suggested by powerful ionized outflow in a galaxy scale.

Keywords: active galaxies; x-ray active galactic nuclei; ultraluminous infrared galaxies
Real-time, Value-driven Data Augmentation in the Era of LSST

The deluge of data from time-domain surveys is rendering traditional human-guided data collection and inference techniques impractical. We propose a novel approach for conducting data collection for science inference in the era of massive large-scale surveys that uses value-based metrics to autonomously strategize and coordinate follow-up in real time. We demonstrate the underlying principles in the Recommender Engine For Intelligent Transient Tracking (REFITT) that ingests live alerts from surveys and value-added inputs from data brokers to predict the future behavior of transients and design optimal data augmentation strategies given a set of scientific objectives. The prototype presented in this paper is tested to work given simulated Rubin Observatory Legacy Survey of Space and Time (LSST) core-collapse supernova (CC SN) light curves from the Photometric LSST Astronomical Time-series Classification Challenge data set. CC SNe were selected for the initial development phase as they are known to be difficult to classify, with the expectation that any learning techniques for them should be at least as effective for other transients. We demonstrate the behavior of REFITT on a random LSST night given ∼32,000 live CC SNe of interest. The system makes good predictions for the photometric behavior of the events and uses them to plan follow-up using a simple data-driven metric. We argue that machine-directed follow-up maximizes the scientific potential of surveys and follow-up resources by reducing downtime and bias in data collection.

Keywords: astronomy data acquisition; surveys; supernovae; core-collapse supernovae
The GOGREEN Survey: Evidence of an Excess of Quiescent Disks in Clusters at 1.0

We present the results of the measured shapes of 832 galaxies in 11 galaxy clusters at 1.0 < z < 1.4 from the GOGREEN survey. We measure the axis ratio (q), the ratio of the minor to the major axis, of the cluster galaxies from near-infrared Hubble Space Telescope imaging using Sérsic profile fitting and compare them with a field sample. We find that the median q of both star-forming and quiescent galaxies in clusters increases with stellar mass, similar to the field. Comparing the axis ratio distributions between clusters and the field in four mass bins, the distributions for star-forming galaxies in clusters are consistent with those in the field. Conversely, the distributions for quiescent galaxies in the two environments are distinct, most remarkably in 10.1\leqslant \mathrm{log}(M/{M}_{\odot })\lt 10.5$ where clusters show a flatter distribution, with an excess at low q. Modelling the distribution with oblate and triaxial components, we find that the cluster and field sample difference is consistent with an excess of flattened oblate quiescent galaxies in clusters. The oblate population contribution drops at high masses, resulting in a narrower q distribution in the massive population than at lower masses. Using a simple accretion model, we show that the observed q distributions and quenched fractions are consistent with a scenario where no morphological transformation occurs for the environmentally quenched population in the two intermediate-mass bins. Our results suggest that environmental quenching mechanism(s) likely produce a population that has a different morphological mix than those resulting from the dominant quenching mechanism in the field.

Keywords: galaxy evolution; galaxy clusters; high-redshift galaxy clusters
Fe VII Emission Lines in the Wavelength Range 193-197 Å

The identifications of Fe VII emission lines in the wavelength range 193-197 Å are discussed in the light of new measurements of laboratory spectra and atomic data calculations. This region is of importance to studies of solar spectra from the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft, which has its peak sensitivity at these wavelengths. Ten lines are measured, arising from seven fine structure levels in the 3p53d3 configuration. Two lines have not previously been reported and lead to new experimental energies for the ${({a}^{2}D)}^{3}{F}_{\mathrm{2,3}}$ levels. Updated experimental energies are obtained for the remaining levels. The new atomic model is used to compute theoretical values for the two density diagnostic ratios λ196.21/λ195.39 and λ196.21/λ196.06, and densities are derived from EIS spectra of coronal loop footpoints.

Keywords: atomic spectroscopy; spectroscopy; line intensities; solar extreme ultraviolet emission; solar transition region
Lopsided Satellite Distributions around Isolated Host Galaxies in a ΛCDM Universe

A recent observational study found that the projected spatial distributions of the satellites of bright, isolated host galaxies tend to be lopsided with respect to the locations of the hosts. Here, we examine the spatial distributions of the satellites of a large number of bright, isolated host galaxies that were obtained from mock redshift surveys of a Λ-cold dark matter (ΛCDM) simulation. Host galaxies and their satellites were identified using selection criteria that are identical to those used in the observational study, allowing for a direct comparison of the results for the simulated and observed systems. To characterize the spatial distribution of the satellites, we adopt two statistics: (1) the pairwise clustering of the satellites and (2) the mean resultant length. In agreement with the observational study, we find a strong tendency for satellites in the simulation to be located on the same side of their host, and the signal is most pronounced for the satellites of blue hosts. These lopsided satellite distributions are not solely attributable to incompleteness of the observed satellite catalog or the presence of objects that have been falsely identified as satellites. In addition, satellites that joined their hosts' halos in the distant past (≳8 Gyr) show a pronounced lopsidedness in their spatial distributions and, therefore, the lopsidedness is not solely attributable to the late-time accretion of satellites.

Keywords: dwarf galaxies; companion galaxies; dark matter distribution
Discovery of an Isolated Dark Dwarf Galaxy in the Nearby Universe

Based on a new H I survey using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), combined with the Pan-STARRS1 images, we identified an isolated H I cloud without any optical counterpart, named FAST J0139+4328. The newly discovered H I cloud appears to be a typical disk galaxy since it has a double-peak shape in the global H I profile and an S-like rotation structure in the velocity-position diagram. Moreover, this disk galaxy has an extremely low absolute magnitude (M B > -10.0 mag) and stellar mass (<6.9 ×105 M ⊙). Furthermore, we obtained that the H I mass of this galaxy is (8.3 ± 1.7) ×107 M ⊙, and the dynamical mass to total baryonic mass ratio is 47 ± 27, implying that dark matter dominates over baryons in FAST J0139+4328. These findings provide observational evidence that FAST J0139+4328 is an isolated dark dwarf galaxy with a redshift of z = 0.0083. This is the first time that an isolated dark galaxy has been detected in the nearby universe.

Keywords: extragalactic astronomy
Results of 12 yr of Pulsar Timing at Nanshan. I.

We have used the Nanshan 25 m Radio Telescope at Xinjiang Astronomical Observatory to obtain timing observations of 87 pulsars from 2002 July to 2014 March. Using the "Cholesky" timing analysis method we have determined positions and proper motions for 48 pulsars, 24 of which are improved positions compared to previously published values. We also present the first published proper motions for nine pulsars and improved proper motions for 21 pulsars using the pulsar timing and position-comparison method. The pulsar rotation parameters are derived and are more accurate than previously published values for 36 pulsars. Glitches are detected in three pulsars: PSRs J1722-3632, J1852-0635, and J1957+2831. For the first two, the glitches are large, with Δνg/ν > 10-6, and they are the first detected glitches in these pulsars. PSR J1722-3632 is the second oldest pulsar, with a large glitch. For the middle-age pulsars (τc > 105 yr), the calculated braking indices, $| n| $ , are strongly correlated with τc and the numbers of positive and negative values of n are almost equal. For young pulsars (τc < 105 yr), there is no correlation between $| n| $ and τc and most have n > 0.

Keywords: radio pulsars; neutron stars; pulsars; pulsar timing method
OGLE-2016-BLG-1093Lb: A Sub-Jupiter-mass Spitzer Planet Located in the Galactic Bulge

OGLE-2016-BLG-1093 is a planetary microlensing event that is part of the statistical Spitzer microlens parallax sample. The precise measurement of the microlens parallax effect for this event, combined with the measurement of finite-source effects, leads to a direct measurement of the lens masses and system distance, M host =0.38-0.57 M ⊙ and m p = 0.59-0.87 M Jup, and the system is located at the Galactic bulge (D L ~ 8.1 kpc). Because this was a high-magnification event, we are also able to empirically show that the "cheap-space parallax" concept produces well-constrained (and consistent) results for ∣π E∣. This demonstrates that this concept can be extended to many two-body lenses. Finally, we briefly explore systematics in the Spitzer light curve in this event and show that their potential impact is strongly mitigated by the color constraint.

Keywords: gravitational microlensing exoplanet detection; satellite microlensing parallax