A spectroscopic survey of stars brighter than B=16.6 magnitude in omega Centauri

Abstract

Using the 2dF multi-fibre instrument at the AAT, we have carried out a spectroscopic survey of over 1500 stars brighter than B=16.6 mag, which have been confirmed by the proper motion study of van Leeuwen et al. (2000) to be members of the massive galactic globular cluster, omega Centauri. The survey aimed at sampling the Hertzsprung-Russell Diagram in a uniform way, thus avoiding a bias towards the dominant stellar population and allowing the study of stars with less common properties such as particularly metal-rich or metal-poor stars. Exceptionally, though, emphasis has been given to include as many RR Lyrae variables as possible in order to address the question why these variables are distributed over such a wide observed range in colours -- coinciding with many non-variable stars of similar colours. The potential of the data and analysis are presented together with the first preliminary results.