The GALAH survey: observational overview and Gaia DR1 companion

Abstract

The Galactic Archaeology with HERMES (GALAH) survey is amassive observational project to trace the MilkyWay'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, 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 0.3-3 kpc and giants at 1-10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick discs, 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], [α/Fe]), radial velocity, distance modulus and reddening for 10 680 observations of 9860 Tycho-2 stars, 7894 of which are included in the first Gaia data release. ; SLM and DBZ acknowledge support from Australian Research Council grants DE140100598 and FT110100743. JPM is supported by a UNSW Vice-Chancellor's Research Fellowship. KL and SB acknowledge funds from the Alexander von Humboldt Foundation in the framework of the Sofja Kovalevskaja Award endowed by the Federal Ministry of Education and Research as well as funds from the Swedish Research Council (Grant no. 2015-00415_3) and Marie Sklodowska Curie Actions (Cofund Project INCA 600398). This work was partly supported by the European Union FP7 programme through ERG grant number 320360.