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The GALAH Survey : Second data release

, ; Buder, Sven; Asplund, Martin; Duong, Ly; Kos, Janez; Lind, Karin; Ness, Melissa K.; Sharma, Sanjib; Bland-Hawthorn, Joss and Casey, Andrew R., et al. (2018) In Monthly Notices of the Royal Astronomical Society 478(4). p.4513-4552
Abstract


The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of theMilkyWay, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum... (More)


The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of theMilkyWay, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T
eff
, logg, [Fe/H], [X/Fe], v
mic
, vsin i, AK
S
) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

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type
Contribution to journal
publication status
published
subject
keywords
Methods: data analysis, Methods: observational, Stars: abundances, Stars: fundamental parameters, Surveys, The Galaxy
in
Monthly Notices of the Royal Astronomical Society
volume
478
issue
4
pages
40 pages
publisher
Oxford University Press (OUP)
external identifiers
  • scopus:85050813726
ISSN
0035-8711
DOI
10.1093/mnras/sty1281
language
English
LU publication?
no
id
b0b239bc-89f8-4d91-b98e-cfb65a4a2b7c
date added to LUP
2019-05-29 19:42:25
date last changed
2019-09-22 05:02:19
@article{b0b239bc-89f8-4d91-b98e-cfb65a4a2b7c,
  abstract     = {<p><br>
                            The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of theMilkyWay, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T<br>
                            <sub>eff</sub><br>
                            , logg, [Fe/H], [X/Fe], v<br>
                            <sub>mic</sub><br>
                            , vsin i, AK<br>
                            <sub>S</sub><br>
                            ) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.<br>
                        </p>},
  author       = {,  and Buder, Sven and Asplund, Martin and Duong, Ly and Kos, Janez and Lind, Karin and Ness, Melissa K. and Sharma, Sanjib and Bland-Hawthorn, Joss and Casey, Andrew R. and De Silva, Gayandhi M. and D'Orazi, Valentina and Freeman, Ken C. and Lewis, Geraint F. and Lin, Jane and Martell, Sarah L. and Schlesinger, Katharine J. and Simpson, Jeffrey D. and Zucker, Daniel B. and Zwitter, Tomaž and Amarsi, Anish M. and Anguiano, Borja and Carollo, Daniela and Casagrande, Luca and Čotar, Klemen and Cottrell, Peter L. and Costa, Gary Da and Gao, Xudong D. and Hayden, Michael R. and Horner, Jonathan and Ireland, Michael J. and Kafle, Prajwal R. and Munari, Ulisse and Nataf, David M. and Nordlander, Thomas and Stello, Dennis and Ting, Yuan Sen and Traven, Gregor and Watson, Fred and Wittenmyer, Robert A. and Wyse, Rosemary F.G. and Yong, David and Zinn, Joel C. and Žerjal, Maruša},
  issn         = {0035-8711},
  keyword      = {Methods: data analysis,Methods: observational,Stars: abundances,Stars: fundamental parameters,Surveys,The Galaxy},
  language     = {eng},
  month        = {08},
  number       = {4},
  pages        = {4513--4552},
  publisher    = {Oxford University Press (OUP)},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {The GALAH Survey : Second data release},
  url          = {http://dx.doi.org/10.1093/mnras/sty1281},
  volume       = {478},
  year         = {2018},
}