NOAO >   Observing Info >   Approved Programs >   2001B-0083

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Proposal Information for 2001B-0083


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

CoI: Ata Sarajedini, University of Florida
CoI: Luciana Bianchi, Johns Hopkins University
CoI: Holland Ford, Johns Hopkns University

Title: The Formation and Evolution of M33 From Star Cluster Properties

Abstract: We propose to complete our study of the formation and early evolution of the M33 halo and disk by measuring age, metallicity, and kinematics of its star cluster populations. Optical spectroscopy of ~35 red M33 clusters has established the presence of both disk and halo components. Interestingly, halo clusters in M33 have a very large age spread, ~5-8 Gyr (Sarajedini et al. 1998; Chandar et al. 2001). There are presently an additional 70 known M33 clusters with age estimates (from integrated photometry) older than several Gyrs, which have no metallicity or velocity measurements. We request optical spectra of these M33 clusters to address the following issues: 1) Is the metallicity distribution of old clusters in M33 bimodal, as in the Milky Way and M31? 2) Is there a correlation between the metallicity and kinematics of old M33 clusters, a distinct observational signature of cluster subpopulations in the only two well studied disk systems to date? 3) What fraction of the M33 \it halo population is younger than 10 Gyr? Answers to these questions will allow us to further constrain the early formation of M33. Additionally, the spectra will provide better age estimates for old and intermediate age clusters, allowing us to calculate the specific frequency of globular clusters, which appears (based on photometric ages) to be significantly higher in this galaxy than in other spirals.


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