The GALAH Survey: Observational Overview and Gaia DR1 companion

TL;DR

The GALAH Survey aims to map the Milky Way's formation history by collecting high-resolution spectra of up to one million stars, providing detailed chemical and stellar parameters to understand Galactic evolution.

Contribution

This paper presents the observational plan, methodology, and early data release of the GALAH Survey, including the largest high-resolution spectroscopic dataset for Galactic archaeology.

Findings

Over 200,000 high-quality spectra collected in first two years

First public data catalogue released with stellar parameters for nearly 10,000 stars

Sample includes stars from the thin disk, thick disk, bulge, and halo

Abstract

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$\simeq$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 3 kpc and giants at 1 to 10 kpc. 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.