A spectral atlas of post-main-sequence stars in omega Centauri: kinematics, evolution, enrichment and interstellar medium

Abstract

We present a spectral atlas of the post-main-sequence population of the most massive Galactic globular cluster, omega Centauri. Spectra were obtained of more than 1500 stars selected as uniformly as possible from across the (B, B-V) colour-magnitude diagram of the proper motion cluster member candidates of van Leeuwen et al. (2000). The spectra were obtained with the 2dF multi-fibre spectrograph at the Anglo Australian Telescope, and cover the approximate range lambda~3840-4940 Angstroem. We measure the radial velocities, effective temperatures, metallicities and surface gravities by fitting ATLAS9 stellar atmosphere models. We analyse the cluster membership and stellar kinematics, interstellar absorption in the Ca II K line at 3933 Angstroem, the RR Lyrae instability strip and the extreme horizontal branch, the metallicity spread and bimodal CN abundance distribution of red giants, nitrogen and s-process enrichment, carbon stars, pulsation-induced Balmer line emission on the asymptotic giant branch (AGB), and the nature of the post-AGB and UV-bright stars. Membership is confirmed for the vast majority of stars, and the radial velocities clearly show the rotation of the cluster core. We identify long-period RR Lyrae-type variables with low gravity, and low-amplitude variables coinciding with warm RR Lyrae stars. A barium enhancement in the coolest red giants indicates that 3rd dredge-up operates in AGB stars in omega Cen. This is distinguished from the pre-enrichment by more massive AGB stars, which is also seen in our data. The properties of the AGB, post-AGB and UV-bright stars suggest that RGB mass loss may be less efficient at very low metallicity, [Fe/H]<<-1, increasing the importance of mass loss on the AGB. The catalogue and spectra are made available via CDS.

accepted for publication in MNRAS

References in corpus (7)

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Cited by in corpus (9)

• The Nature of UCDs: Internal Dynamics from an Expanded Sample and Homogeneous Database
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• Fe and Al Abundances for 180 Red Giants in the Globular Cluster Omega Centauri (NGC 5139)
• A Spitzer Space Telescope Atlas of omega Centauri: The Stellar Population, Mass Loss, and the Intracluster Medium
• Detailed maps of interstellar clouds in front of omega Centauri: Small-scale structures in the Galactic Disc-Halo interface
• A Spectroscopic Survey for Omega Centauri Members at and beyond the Cluster Tidal Radius
• A Spitzer search for cold dust within globular clusters
• Testing the AGB Scenario as the Origin of the Extreme-Helium Population in omega Centauri
• MAD@VLT: Deep into the Madding Crowd of Omega Centauri