The GALAH Survey: Scientific Motivation
  The GALAH survey is a large high-resolution spectroscopic survey using the
newly commissioned HERMES spectrograph on the Anglo-Australian Telescope. The
HERMES spectrograph provides high-resolution (R ~28,000) spectra in four
passbands for 392 stars simultaneously over a 2 degree field of view. The goal
of the survey is to unravel the formation and evolutionary history of the Milky
Way, using fossil remnants of ancient star formation events which have been
disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks
to identify such dispersed remnants solely from their common and unique
chemical signatures; these groups are unidentifiable from their spatial,
photometric or kinematic properties. To carry out chemical tagging, the GALAH
survey will acquire spectra for a million stars down to V~14. The HERMES
spectra of FGK stars contain absorption lines from 29 elements including light
proton-capture elements, alpha-elements, odd-Z elements, iron-peak elements and
n-capture elements from the light and heavy s-process and the r-process. This
paper describes the motivation and planned execution of the GALAH survey, and
presents some results on the first-light performance of HERMES.
