- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3203
- Title:
- GALAH observational overview
- Short Name:
- J/MNRAS/465/3203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Archaeology with HERMES (GALAH) Survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R~28,000) spectra taken with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope (AAT), GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3 to 3kpc and giants at 1 to 10kpc. This enables a thorough local chemical inventory of the Galactic thin and thick disks, and also captures smaller samples of the bulge and halo. In this paper we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200,000 stars. We also present the first public GALAH data catalogue: stellar parameters (Teff, log(g), [Fe/H], [alpha/Fe]), radial velocity, distance modulus and reddening for 10680 observations of 9860 Tycho-2 stars that may be included in the first Gaia data release.
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- ID:
- ivo://CDS.VizieR/J/ApJ/872/95
- Title:
- GALEX and Gaia data for APOGEE red clump stars
- Short Name:
- J/ApJ/872/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although core helium-burning red clump (RC) stars are faint at ultraviolet wavelengths, their ultraviolet (UV)-optical color is a unique and accessible probe of their physical properties. Using data from the Galaxy Evolution Explorer All Sky Imaging Survey (GALEX AIS), Gaia Data Release 2, and the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR14 survey, we find that spectroscopic metallicity is strongly correlated with the location of an RC star in the UV-optical color-magnitude diagram. The RC has a wide spread in (NUV-G)_0_ color of over 4mag compared to a 0.7mag range in (G_BP_-G_RP_)_0_. We propose a photometric, dust-corrected, UV-optical (NUV-G)_0_ color-metallicity [Fe/H] relation using a sample of 5175 RC stars from APOGEE. We show that this relation has a scatter of 0.16dex and is easier to obtain for large, wide-field samples than for spectroscopic metallicities. Importantly, the effect may be comparable to the spread in RC color attributed to extinction in other studies.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/37
- Title:
- GALEX catalog of star clusters in M31
- Short Name:
- J/ApJS/199/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive catalog of 700 confirmed star clusters in the field of M31 compiled from three major existing catalogs. We detect 418 and 257 star clusters in Galaxy Evolution Explorer near-ultraviolet and far-ultraviolet (FUV) imaging, respectively. Our final catalog includes photometry of star clusters in up to 16 passbands ranging from FUV to NIR as well as ancillary information such as reddening, metallicity, and radial velocities. In particular, this is the most extensive and updated catalog of UV-integrated photometry for M31 star clusters. Ages and masses of star clusters are derived by fitting the multi-band photometry with model spectral energy distribution (SED); UV photometry enables more accurate age estimation of young clusters. Our catalog includes 182 young clusters with ages less than 1Gyr. Our estimated ages and masses of young clusters are in good agreement with previously determined values in the literature. The mean age and mass of young clusters are about 300Myr and 10^4^M_{sun}_, respectively.
- ID:
- ivo://CDS.VizieR/J/AJ/151/7
- Title:
- Globular and open clusters observed by SDSS/SEGUE
- Short Name:
- J/AJ/151/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present griz observations for the clusters M92, M13 and NGC 6791 and gr photometry for M71, Be 29 and NGC 7789. In addition we present new membership identifications for all these clusters, which have been observed spectroscopically as calibrators for the Sloan Digital Sky Survey (SDSS)/SEGUE survey; this paper focuses in particular on the red giant branch stars in the clusters. In a number of cases, these giants were too bright to be observed in the normal SDSS survey operations, and we describe the procedure used to obtain spectra for these stars. For M71, we also present a new variable reddening map and a new fiducial for the gr giant branch. For NGC 7789, we derived a transformation from T_eff_ to g-r for giants of near solar abundance, using IRFM T_eff_ measures of stars with good ugriz and 2MASS photometry and SEGUE spectra. The result of our analysis is a robust list of known cluster members with correctly dereddened and (if needed) transformed gr photometry for crucial calibration efforts for SDSS and SEGUE.
- ID:
- ivo://CDS.VizieR/J/AJ/158/192
- Title:
- He II emission from Wolf-Rayet stars in MW & LMC
- Short Name:
- J/AJ/158/192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calibrated a technique to measure dust attenuation in star-forming galaxies. The technique utilizes the stellar-wind lines in Wolf-Rayet stars, which are widely observed in galaxy spectra. The He II 1640 and 4686 features are recombination lines whose ratio is largely determined by atomic physics. Therefore they can serve as a stellar dust probe in the same way as the Balmer lines are used as a nebular probe. We measured the strength of the He II 1640 line in 97 Wolf-Rayet stars in the Galaxy and the Large Magellanic Cloud. The reddening corrected fluxes follow a tight correlation with a fixed ratio of 7.76 for the He II 1640 to 4686 line ratio. Dust attenuation decreases this ratio. We provide a relation between the stellar E(B-V) and the observed line ratio for several attenuation laws. Combining this technique with the use of the nebular Balmer decrement allows the determination of the stellar and nebular dust attenuation in galaxies and can probe its effects at different stellar age and mass regimes, independently of the initial mass function and the star formation history. We derived the dust reddening from the He II line fluxes and compared it to the reddening from the Balmer decrement and from the slope of the ultraviolet continuum in two star-forming galaxies. The three methods result in dust attenuations which agree to within the errors. Future application of this technique permits studies of the stellar dust attenuation compared to the nebular attenuation in a representative galaxy sample.
- ID:
- ivo://CDS.VizieR/II/354
- Title:
- HIP and TGAS stars reddening and extinction
- Short Name:
- II/354
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- These reddening and interstellar extinction estimates are a result of a series of studies presented in the papers 2009AstL...35..780G, 2010AstL...36..584G, 2012AstL...38...12G, 2012AstL...38...87G, 2017AstL...43..472G and finally 2017MNRAS.472.3805G and 2018MNRAS.475.1121G. The key basis of these estimates is the 3D reddening map of Gontcharov (2017AstL...43..472G, 2017PAZh...43..521G, Cat. J/PAZh/43/521). This map has been tested among eight sources of reddening and extinction estimates for nearly 60,000 Gaia DR1 TGAS main sequence stars younger than 3Gyr with a relative error of the Gaia parallax less than 0.1. The sources are tested in their ability to put the stars among the PARSEC and MIST theoretical isochrones in the Hertzsprung-Russell diagram based on the precise Gaia, Tycho-2, 2MASS and WISE photometry. The 3D reddening map of Gontcharov provides both the minimal number of outliers bluer than any reasonable isochrone and the correct number of stars younger than 3Gyr in agreement with the Besancon Galaxy model. In another test Gaia DR1 TGAS parallaxes, Tycho-2 photometry and reddening/extinction estimates from nine data sources for 38,074 giants within 415pc from the Sun are used to compare their position in the Hertzsprung-Russell diagram with theoretical estimates, which are based on the PARSEC and MIST isochrones and the TRILEGAL model of the Galaxy with its parameters being widely varied. We conclude that, again, the estimates from the 3D reddening map of Gontcharov, including the median reddening E(B-V)=0.06mag at |b|>50{deg}, give the best fit of the empirical and theoretical data with each other. Based on these studies we present here the best up-to-date reddening, extinction and extinction-to-reddening estimates for the Gaia DR1 TGAS and Hipparcos stars within 415pc from the Sun. The accuracy of the E(B-V) estimates is proved to be better than 0.04mag everywhere in this space.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/15
- Title:
- HST/COS obs. of QSO outflows in 500-1050{AA}. VII.
- Short Name:
- J/ApJS/249/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From Hubble Space Telescope/Cosmic Origins Spectrograph spectra of five quasars, 16 outflows are detected. For 11 outflows, we are able to constrain their distances to the central source (R) and their energetics. In instances of multiple electron number density determinations (used in the calculation of R) for the same outflow, the values are consistent within errors. For the 11 outflows, eight have measurements for R (between 10 and 1000pc), one has a lower limit, another has an upper limit, and the last has a range in R. There are two outflows that have enough kinetic luminosity to be major contributors to active galactic nucleus feedback. The outflowing mass is found primarily in a very high-ionization phase, which is probed using troughs from, e.g., Ne VIII, Na IX, Mg X, and Si XII. Such ions connect the physical conditions of these ultraviolet outflows to the X-ray warm absorber outflows seen in nearby Seyfert galaxies. The ion Cl VII and several new transitions from Ne V have been detected for the first time.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/42
- Title:
- Improved reddenings for 59 Galactic Cepheids
- Short Name:
- J/ApJ/842/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometric method by which improved high-precision reddenings and true distance moduli can be determined to individual Galactic Cepheids once distance measurements are available. We illustrate that the relative positioning of stars in the Cepheid period-luminosity (PL) relation (Leavitt law) is preserved as a function of wavelength. This information then provides a powerful constraint for determining reddenings to individual Cepheids, as well as their distances. As a first step, we apply this method to the 59 Cepheids in the compilation of Fouque et al. Updated reddenings, distance moduli (or parallaxes), and absolute magnitudes in seven (optical through near-infrared) bands are given. From these intrinsic quantities, multiwavelength PL and color-color relations are derived. We find that the V-band period-luminosity-color relation has an rms scatter of only 0.06mag, so that individual Cepheid distances can be measured to 3%, compared with dispersions of 6 to 13% for the one-parameter K through B PL relations, respectively. This method will be especially useful in conjunction with the new accurate parallax sample upcoming from Gaia.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/91
- Title:
- Interferometric obs. of B-type stars with CHARA
- Short Name:
- J/ApJ/873/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present interferometric observations of 25 spectral type-B stars that were made with the Precision Astronomical Visible Observations and the CLassic Interferometry with Multiple Baselines beam combiners at the Center for High Angular Resolution Astronomy Array (CHARA). The observations provide the angular sizes of these stars with an average error of 6%. The stars range in size from 1.09mas for {beta} Tau down to 0.20mas for 32 Ori. We collected ultraviolet to infrared spectrophotometry and derived temperatures, angular diameters, and reddening estimates that best fit the spectra, as well as solutions with the angular size fixed by the interferometric measurements. There is generally good agreement between the observed and spectral fit angular diameters, indicating that the fluxes predicted from model atmospheres are reliable. On the other hand, the temperatures derived from angular diameters and fluxes tend to be larger (by ~4%) than those from published results based on analysis of the line spectrum. This discrepancy may in part be attributed to unexplored atmospheric parameters or the existence of unknown companions. The physical radii of the stars are calculated from the angular diameters and Gaia DR2 parallaxes, and the target stars are placed in the Hertzsprung-Russell diagram for comparison with evolutionary tracks.
- ID:
- ivo://CDS.VizieR/J/ApJ/726/19
- Title:
- Intermediate-mass stars in IC 1805
- Short Name:
- J/ApJ/726/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a study of the intermediate- and high-mass stars in the young, rich star-forming complex IC 1805, based on a combination of optical, near-infrared, and mid-infrared photometry, and classification spectra. These data provide the basis for characterizing the masses and ages for stars more massive than ~2M_{sun}_ and enable a study of the frequency and character of circumstellar disks associated with intermediate- and high-mass stars. Optically thick accretion disks among stars with masses 2<M/M_{sun}_<4 are rare (~2% of members) and absent among more massive stars. A larger fraction (~10%) of stars with masses 2<M/M_{sun}_<4 appear to be surrounded by disks that have evolved from the initial optically thick accretion phase. We identify four classes of such disks. These classes are based on spectral energy distributions (SEDs) of excess emission above photospheric levels: disks that are (1) optically thin based on the magnitude of the observed excess emission from 2 to 24um, (2) optically thin in their inner regions (r<20AU) and optically thick in their outer regions, (3) exhibit empty inner regions (r<10AU) and optically thin emission in their outer regions, and (4) exhibit empty inner regions and optically thick outer regions. We discuss, and assess the merits and liabilities of, proposed explanations for disks exhibiting these SED types and suggest additional observations that would test these proposals.
