Sazuna/UAT_keywords huggingface dataset:
Clustering of Local Group Distances: Publication Bias or Correlated Measurements? VI. Extending to Virgo Cluster Distances. We have established an internally consistent Local Group distance framework, using the Galactic Center, the Large Magellanic Cloud, and Messier 31 (M31) as important stepping stones. At greater distances, few distance benchmarks are available. As a consequence, M87 and/or Virgo cluster distances are often invoked as the next rung on the ladder to more distant objects such as the Fornax and Coma clusters. Therefore, we extensively mined the published literature for independently derived distance estimates to either M87 or the center of the Virgo cluster. Based on our newly compiled, comprehensive database of 213 such distances, published between 1929 and 2017 July, we recommend an outward extension to our distance framework, (m-M{)}0{{M}87}=31.03+/- 0.14 mag (D = 16.07 ± 1.03 Mpc; where the uncertainty represents the Gaussian σ of the distribution), based on a subset of recent (post-1990) M87/Virgo cluster distance measurements. The most stable distance tracers employed here were derived from analysis of both primary and secondary distance indicators. Among the former, we preferentially rely on Cepheid period-luminosity relations and red-giant-branch terminal magnitudes; our preferred secondary distance tracers are surface brightness fluctuations. Our updated distance modulus to M87 implies a slightly reduced black hole mass of (5.9 ± 0.6) × 109 M ⊙ with respect to that determined by the Event Horizon Telescope collaboration.

Keywords: Galaxy distances, Astronomy databases, Virgo Cluster, Distance measure, Astronomical reference materials
The Separation Distribution of Ultrawide Binaries across Galactic Populations. We present an extensive and pure sample of ultrawide binary stars with separations of 0.01 ≲ s/pc ≲ 1 in the solar neighborhood. Using data from Gaia DR2, we define kinematic subpopulations via the systems’ tangential velocities, I.e., disk-like (V ⊥,tot ≤ 40 km s-1), intermediate (V ⊥,tot = 40-85 km s-1), and halo-like (V ⊥,tot ≥ 85 km s-1) binaries, presuming that these velocity cuts represent a rough ordering in the binaries’ age and metallicity. Through stringent cuts on astrometric precision, we can obtain pure binary samples at such wide separations with thousands of binaries in each sample. Fitting a smoothly broken power law for the separation distribution, we find that its slope at s = 102.5-4 au is the same for all subpopulations, p(s) ∝ s  γ  with γ ≈ -1.54. However, the logarithmic slope of p(s) steepens at s ≳ 104 au. We find some evidences that the degree of steepening increases with the binaries’ age, with a slope change of only Δγ ≈ 0.5 for disk-like stars, but Δγ ≳ 1 for halo-like stars. This trend is contrary to what might be expected if steepening at wide separations were due to gravitational perturbations by molecular clouds or stars, which would preferentially disrupt disk binaries. If we were to interpret steepening at s ≳ 104 au as a consequence of disruption by MAssive Compact Halo Objects (MACHOs), we would have to invoke a MACHO population inconsistent with other constraints. As a more plausible alternative, we propose a simple model to predict the separation distribution of wide binaries formed in dissolving star clusters. This model generically predicts γ ≃ -1.5 as observed, with steepening at larger separations due to the finite size of binaries’ birth clusters.

Keywords: Galaxy stellar disks, Binary stars, Galaxy stellar content, Astrostatistics, Galaxy stellar halos, Astrometric binary stars, Star formation, Visual binary stars
Nonlinear Convergence of Solar-like Stars Chromospheres Using Millimeter, Submillimeter, and Infrared Observations. In this work, we present a new methodology to fit the observed and synthetic spectrum of solar-like stars at millimeter, submillimeter, and infrared wavelengths through semiempirical models of the solar chromosphere. We use the Levenberg-Marquardt algorithm as a Nonlinear method, PakalMPI as the semiempirical model of the solar chromosphere, and recent observations from the Atacama Large Millimeter/submillimeter Array of Alpha Centauri A as a test case. Our results show that we can use solar chromospheric semiempirical models as an input model to reproduce the observed spectrum of solar-like stars. The new profiles show similarities to the solar chromosphere as a minimum of temperature (without the restriction from CO emission) and a plateau in the high chromosphere. Our method provides a new fast numerical tool to estimate the physical conditions of solar-like stars.

Keywords: Astronomical models, Quiet solar chromosphere, Millimeter astronomy, Stellar chromospheres, Far infrared astronomy, Solar electromagnetic emission, Submillimeter astronomy, Algorithms
Synthetic Gaia Surveys from the FIRE Cosmological Simulations of Milky Way-mass Galaxies. With Gaia Data Release 2, the astronomical community is entering a new era of multidimensional surveys of the Milky Way. This new phase-space view of our Galaxy demands new tools for comparing observations to simulations of Milky Way-mass galaxies in a cosmological context, to test the physics of both dark matter and galaxy formation. We present ananke, a framework for generating synthetic phase-space surveys from high-resolution baryonic simulations, and use it to generate a suite of synthetic surveys resembling Gaia DR2 in data structure, magnitude limits, and observational errors. We use three cosmological simulations of Milky Way-mass galaxies from the Latte suite of the Feedback In Realistic Environments project, which feature self-consistent clustering of star formation in dense molecular clouds and thin stellar/gaseous disks in live cosmological halos with satellite dwarf galaxies and stellar halos. We select three solar viewpoints from each simulation to generate nine synthetic Gaia-like surveys. We sample synthetic stars by assuming each star particle (of mass 7070 M ⊙) represents a single stellar population. At each viewpoint, we compute dust extinction from the simulated gas metallicity distribution and apply a simple error model to produce a synthetic Gaia-like survey that includes both observational properties and a pointer to the generating star particle. We provide the complete simulation snapshot at z = 0 for each simulated galaxy. We describe data access points, the data model, and plans for future upgrades. These synthetic surveys provide a tool for the scientific community to test analysis methods and interpret Gaia data.

Keywords: Astrometry, Astronomical simulations
A Large-scale <SUP>12</SUP>CO, <SUP>13</SUP>CO, and C<SUP>18</SUP>O Molecular Cloud Survey in the Outer Galactic Plane over I = [129.°75, 140.°25] and b = [-5.°25, +5.°25]. We present the data of an unbiased J = 1-0 12CO/13CO/C18O survey of molecular clouds in the Galactic plane over l = [129.°75, 140.°25] and b = [-5.°25, +5.°25]. For the full 10.°5 × 10.°5 region sampled at 30″, there are 1,590,120 spectra for each isotopologue. The high sensitivity and large spatial dynamic range of the maps provide valuable insights into the structure, physical properties, and kinematics of the molecular gas. The new data successfully trace the most distant spiral arm, as well as the internal subfeatures of the nearby spiral arms. The combined data set of 12CO, 13CO, and C18O allows us to make a more accurate inventory of gas column density and mass for molecular gas within this Galactic interval than hitherto attempted. A statistical analysis reveals that a large fraction of the observed molecular gas is emitted from regions with low excitation conditions. As expected, a considerable amount of H2 mass is found to be confined to the spiral arms. Moreover, we find that the C18O emission is exclusively seen along spiral arms at current detection limits. The physical properties of molecular gas vary considerably in different spiral arms and inter-arms. We find that the column density probability density functions and the amount of relatively denser gas (traced by 13CO or C18O) appear to be closely related to the level of massive star formation activity within the molecular gas. The high-quality data also reveal that the warp and flare of the Galactic plane become obvious beyond the Perseus arm in this Galactic longitude range.

Keywords: Surveys, Galaxy structure, Molecular clouds, Star formation, Interstellar medium, CO line emission
RR Lyrae Star Candidates from SDSS Databases by Cost-sensitive Random Forests. With the increase of known RR Lyrae stars, it is reliable to create classifiers of RR Lyrae stars based on their photometric data or combined photometric and spectroscopic data. Nevertheless the total number of known RR Lyrae stars is still too small compared with the large survey databases. So classification of RR Lyrae stars and other sources belongs to imbalanced learning. Based on Sloan Digital Sky Survey (SDSS) photometric and spectroscopic data, we apply cost-sensitive Random Forests fit for imbalanced learning to preselect RR Lyrae star candidates. Only with photometric data, u-g,g-r,r-I,I-z is the best input pattern. While also considering physical parameters (T eff, [Fe/H], log(g)), the optimal input pattern is T eff, [Fe/H], log(g), u-g,g-r,r-I,I-z, at this moment for cost-sensitive Random Forests, the performance metrics of completeness, contamination, and Matthews correlation coefficient are 0.975, 0.019, and 0.975, respectively. It indicates that adding stellar physical parameters is helpful for identifying RR Lyrae stars from other stars. We apply the best classifiers on the SDSS photometric data and combined photometric data with physical parameters to select RR Lyrae star candidates. Finally 11,041 photometric candidates with spectral type A and F are obtained, and then 304 candidates with physical parameters are selected out. Among the 304 candidates, a small part are HB stars, BS stars, RGB stars, and peculiar stars, and the rest are unknown in the Simbad database. These candidates may be used as the input catalog for time-series follow-up observations.

Keywords: Astronomy databases, Astronomy data analysis, Astrostatistics, RR Lyrae variable stars, Stellar types, Random Forests, Metallicity
Deriving the Stellar Labels of LAMOST Spectra with the Stellar LAbel Machine (SLAM). The LAMOST survey has provided 9 million spectra in its Data Release 5 (DR5) at R ∼ 1800. Extracting precise stellar labels is crucial for such a large sample. In this paper, we report the implementation of the Stellar LAbel Machine (SLAM), which is a data-driven method based on support vector regression (SVR), a robust nonlinear regression technique. Thanks to the capability to model highly nonlinear problems with SVR, SLAM can generally derive stellar labels over a wide range of spectral types. This gives it a unique capability compared to other popular data-driven methods. To illustrate this capability, we test the performance of SLAM on stars ranging from T eff ∼ 4000 to ∼8000 K trained on LAMOST spectra and stellar labels. At g-band signal-to-noise ratio (S/N g ) higher than 100, the random uncertainties of T eff, log g, and [Fe/H] are 50 K, 0.09 dex, and 0.07 dex, respectively. We then set up another SLAM model trained by APOGEE and LAMOST common stars to demonstrate its capability of dealing with high dimensional problems. The spectra are from LAMOST DR5 and the stellar labels of the training set are from APOGEE DR15, including T eff, log g, [M/H], [α/M], [C/M], and [N/M]. The cross-validated scatters at {{S}}/{{{N}}}g∼ 100 are 49 K, 0.10 dex, 0.037 dex, 0.026 dex, 0.058 dex, and 0.106 dex for these parameters, respectively. This performance is at the same level as other up-to-date data-driven models. As a byproduct, we also provide the latest catalog of ∼1 million LAMOST DR5 K giant stars with SLAM-predicted stellar labels in this work.

Keywords: Bayesian statistics, Fundamental parameters of stars, Stellar abundances, Surveys, Astronomy data analysis, Chemical abundances, Astronomical methods, Catalogs
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 &amp; 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: High resolution spectroscopy, Spectral line lists, Spectral line identification, Spectroscopy, Late-type giant stars, Late-type supergiant stars, Late-type dwarf stars, Stellar spectral lines, Near infrared astronomy
Search for Nearby Earth Analogs. II. Detection of Five New Planets, Eight Planet Candidates, and Confirmation of Three Planets around Nine Nearby M Dwarfs. Zechmeister et al. surveyed 38 nearby M dwarfs from 2000 to 2007 March with VLT2 and the Ultraviolet and Visual Echelle Spectrograph (UVES) spectrometer. These data have recently been reanalyzed, yielding a significant improvement in the Doppler velocity precision. Spurred by this, we have combined the UVES data with velocity sets from High Accuracy Radial velocity Planet Searcher, Magellan/Planet Finder Spectrograph, and Keck/High Resolution Echelle Spectrometer. Sixteen planet candidates have been uncovered orbiting nine M dwarfs. Five of them are new planets corresponding to radial velocity signals, which are not sensitive to the choice of noise models and are identified in multiple data sets over various time spans. Eight candidate planets require additional observation to be confirmed. We also confirm three previously reported planets. Among the new planets, GJ 180 d and GJ 229A c are super-Earths located in the conservative habitable zones of their host stars. We investigate their dynamical stability using the Monte Carlo approach and find both planetary orbits are robust to the gravitational perturbations of the companion planets. Due to their proximity to the Sun, the angular separation between the host stars and the potentially habitable planets in these two systems is 25 and 59 mas, respectively. They are thus good candidates for future direct imaging by James Webb Space Telescope and E-ELT. In addition, we find GJ 433 c, a cold super-Neptune belonging to an unexplored population of Neptune-like planets. With a separation of 0.″5 from its host star, GJ 433 c is probably the first realistic candidate for the direct imaging of cold Neptunes. A comprehensive survey of these planets is important for the studies of planet formation. This paper includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile.

Keywords: M dwarf stars, High resolution spectroscopy, Exoplanet detection methods, Astrostatistics, Exoplanet astronomy, Radial velocity
Compact Groups of Galaxies in Sloan Digital Sky Survey and LAMOST Spectral Survey. I. The Catalogs. A compact group (CG) is a kind of special galaxy system where the galaxy members are separated at distances of the order of galaxy size. The strong interaction between the galaxy members makes CGs ideal labs for studying the environmental effects on galaxy evolution. The traditional photometric selection algorithm biases against the CG candidates at low redshifts, while the spectroscopic identification technique is affected by the spectroscopic incompleteness of sample galaxies and typically biases against the high redshift candidates. In this study, we combine these two methods and select CGs in the main galaxy sample of the Sloan Digital Sky Survey, where we also have taken the advantages of the complementary redshift measurements from the LAMOST spectral and GAMA surveys. We have obtained the largest and most complete CG samples to date. Our samples include 6144 CGs and 8022 CG candidates, which are unique in the studies of the nature of the CGs and the evolution of the galaxies inside.

Keywords: Hickson compact group, Galaxy groups, Diamond ring effect, Galaxy environments
Reconstructing Functions and Estimating Parameters with Artificial Neural Networks: A Test with a Hubble Parameter and SNe Ia. In this work, we propose a new nonparametric approach for reconstructing a function from observational data using an Artificial Neural Network (ANN), which has no assumptions about the data and is a completely data-driven approach. We test the ANN method by reconstructing functions of the Hubble parameter measurements H(z) and the distance-redshift relation DL(z) of Type Ia supernovae. We find that both H(z) and DL(z) can be reconstructed with high accuracy. Furthermore, we estimate cosmological parameters using the reconstructed functions of H(z) and DL(z) and find the results are consistent with those obtained using the observational data directly. Therefore, we propose that the function reconstructed by ANN can represent the actual distribution of observational data and can be used for parameter estimation in further cosmological research. In addition, we present a new strategy for training and evaluating the neural network, and a code for reconstructing functions using ANN has been developed and will be available.

Keywords: Cosmological models, Neural networks, Cosmological parameters, Observational cosmology, Astronomy data analysis, Computational methods
Line Lists for the {{X}}(1) {{\Sigma }}(+) State of CS. Rotation-vibrational line lists for eight isotopologues of carbon monosulphide (CS; 12C32S, 12C33S, 12C34S, 12C36S,13C32S, 13C33S,13C34S, and 13C36S) in their ground electronic state (X1Σ+) are calculated. An empirical potential function with the corrections of Born-Oppenheimer breakdown effects, which are determined by a direct potential fitting approach using over 4300 observed transition frequencies of 12C32S, 12C33S, 12C34S, and 13C32S, is used in line list calculations. The reproduced transition frequencies are within the observation uncertainties for the isotopologues with experimental data. The dipole moment functions are calculated using an ab initio method at a multireference configuration interaction method/cc-pv5z level with a large active space of electronic configuration. The dipole moment at equilibrium nuclear separation is almost identical to the experimental result. The calculated intensities agree excellently with the laboratory observations at 2573 K. The corresponding Einstein A coefficients and oscillator strengths are predicted. Partition functions for temperatures up to 7500 K have been calculated. The line lists can be used for spectroscopic measurements of CS in astronomical environments of various temperatures.

Keywords: Spectral line lists
A Catalog of Periodic Variables in Open Clusters M35 and NGC 2158. We present a catalog of 1143 periodic variables, compiled from our image-subtracted photometric analysis of the K2 Campaign-0 super stamp. This super stamp is centered on the open clusters M35 and NGC 2158. Approximately 46% of our periodic variables were previously unreported. Of the catalog variables, we find that 331 are members of M35 and 56 are members of NGC 2158 ( ${P}_{{\rm{m}}}\,\gt \,0.5$ ). Our catalog contains two new transiting exoplanet candidates, both of which orbit field stars. The smaller planet candidate has a radius of 0.35 ± 0.04 ${R}_{{\rm{J}}}$ and orbits a K dwarf ( ${K}_{{\rm{p}}}$ = 15.4 mag) with a transit depth of 2.9 millimag. The larger planet candidate has a radius of 0.72 ± 0.02 ${R}_{{\rm{J}}}$ and orbits a late G-type star ( ${K}_{{\rm{p}}}$ = 15.7 mag) with a transit depth of 2.2 millimag. The larger planet candidate may be an unresolved binary or a false alarm. Our catalog includes 44 eclipsing binaries (EBs), including ten new detections. Of the EBs, one is an M35 member and five are NGC 2158 members. Our catalog contains a total of 1097 nontransiting variable stars, including a field δ Cepheid exhibiting double mode pulsations, 561 rotational variables, and 251 pulsating variables (primarily γ Doradus and δ Scuti types). The periods of our catalog sources range between 43 minutes to 24 days. The known ages of our reported cluster variables will facilitate investigations of a variety of stellar evolutionary processes.

Keywords: Transit photometry
Quasar Accretion Disk Sizes from Continuum Reverberation Mapping in the DES Standard-star Fields. Measurements of the physical properties of accretion disks in active galactic nuclei are important for better understanding the growth and evolution of supermassive black holes. We present the accretion disk sizes of 22 quasars from continuum reverberation mapping with data from the Dark Energy Survey (DES) standard-star fields and the supernova C fields. We construct continuum light curves with the griz photometry that span five seasons of DES observations. These data sample the time variability of the quasars with a cadence as short as 1 day, which corresponds to a rest-frame cadence that is a factor of a few higher than most previous work. We derive time lags between bands with both JAVELIN and the interpolated cross-correlation function method and fit for accretion disk sizes using the JAVELIN thin-disk model. These new measurements include disks around black holes with masses as small as ∼107 M⊙, which have equivalent sizes at 2500 Å as small as ∼0.1 lt-day in the rest frame. We find that most objects have accretion disk sizes consistent with the prediction of the standard thin-disk model when we take disk variability into account. We have also simulated the expected yield of accretion disk measurements under various observational scenarios for the Large Synoptic Survey Telescope Deep Drilling Fields. We find that the number of disk measurements would increase significantly if the default cadence is changed from 3 days to 2 days or 1 day.

Keywords: Accretion, Supermassive black holes, Quasars, Reverberation mapping, Active galactic nuclei