The Interplay Between Globular Clusters and the Halo and Disk

¹ Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire, ST5 5BG, UK
² Department of Astronomy, School of Physics and Astronomy, 116 Church Street, S.E., University of Minnesota, Minneapolis, MN 55455, USA

Abstract

Globular clusters (GC) are powerful tools to analyse the Halo environment: spread throughout the Halo at distances of 2– 122 kpc, moving with space velocities of ∼200 km s⁻¹, they provide unique tracers of local Halo conditions. Each cluster enriches the Halo with several M_⊙ Myr⁻¹ through stellar winds. The interaction of these winds with the Halo can be used as a probe of the local Halo environment.

Using spectral energy distributions of 6875 stars in the GC ω Cen, we quantify the cluster’s total mass loss. Comparing this to observed limits on intra-cluster material (ICM), we find the ICM is being cleared from these clusters on timescales of <10⁵ yr. We also present new 21 cm observations of the high velocity H i cloud near ω Cen in the context of recent Spitzer observations, discussing its structure and likely associations.