NOAO >   Observing Info >   Approved Programs >   2001B-0209

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Proposal Information for 2001B-0209


PI: Rupali Chandar, Johns Hopkins University, rupali@pha.jhu.edu
Address: 3701 San Martin Dr., Baltimore, MD 21218, USA

CoI: Holland Ford, Johns Hopkins University
CoI: Zlatan Tsvetanov, Johns Hopkins University

Title: The Metallicity Distribution and Kinematics of Globular Clusters in M81

Abstract: To date, the ages, metallicities, and kinematics of globular cluster systems (GCS) have only been well studied in two spiral galaxies, the Milky Way and M31. Because GCS provide information on the conditions present during the formation and early epochs of their parent galaxies, understanding their properties is crucial for a complete theory of the galaxy formation process. To extend the study of old stellar populations to another spiral galaxy, we have compiled a catalog of 114 star clusters in the nearby Sab galaxy M81, from HST WFPC2 multiband imaging. This galaxy is of an earlier-type than M31 and the Milky Way, thus extending the range of correlations between morphological type and GCS. We propose to obtain multislit, optical spectroscopy of ~90 of our brightest GC candidates in M81. For the brighter half of our sample we will be able to measure individual ages, metallicities and velocities, and for the fainter half of the sample we will obtain individual velocities. This information will be used to explore the following: 1) is there evidence for a bimodal metallicity distribution in the M81 GCS, as found in M31 and the Milky Way? 2) is there a correlation between metallicity and kinematics? 3) is there an obvious age spread among halo cluster candidates, or a detectable metallicity gradient? The proposed observations will provide direct constraints for the formation and evolution of M81, and will allow us to start making global conclusions concerning spheroid formation in spiral galaxies.


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