Carbon Abundances From SDSS Globular Clusters: Exploring the Origin in the Large Spread in [C/Fe]

Abstract

Globular clusters were once thought to be chemically homogeneous systems with a single stellar population. However, recent results suggest the presence of more than one stellar population among most all globular clusters. These stars have a different abundance pattern compared to halo stars of similar metallicities. To understand globular cluster formation in the context of hierarchical Galaxy formation models, it is necessary to understand the origin of their abundance patterns. We have used the SDSS spectra from Data Release 8 to estimate the carbon abundances for member stars in 5 globular clusters. We find large spreads in the carbon abundances throughout the CMDs of the clusters, indicating multiple populations with different carbon abundances.