NOAO >   Observing Info >   Approved Programs >   2006B-0302

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Proposal Information for 2006B-0302


PI: Ata Sarajedini, University of Florida, ata@astro.ufl.edu
Address: Astronomy Department, P. O. Box 112055, Gainesville, FL, USA

CoI: Mike Barker, University of Florida

Title: The Star Formation History of M33's Outer Regions

Abstract: The halos of disk galaxies are believed to contain the first stars formed in these systems. As such, their properties reflect those present during the early epochs of galaxy formation and thus hold the clues to several long-standing questions. In the Local Group, only three galaxies, the Milky Way, M31, and M33, possess classical halo populations. The stars in these halos are either members of star clusters or members of the field population. To obtain a complete picture of the stellar content of a galactic halo, both the cluster and field stars must be characterized. In the case of M33, several studies have concluded that the halo clusters span an age range (5-7 Gyr) that is substantially greater than that present among the halo globular clusters (GCs) of the Milky Way (2-3 Gyr). This suggests that the formation of the M33 halo GCs proceeded quite differently as compared with the Milky Way halo GCs. In contrast, we know very little about the halo \bf field population of M33. Not only is there a dearth of information regarding the ages and abundances of the field stars, but we know almost nothing about the structure and extent of the M33 field halo population. The present proposal will begin to remedy this situation by constructing deep color-magnitude diagrams for a large region extending from 20 to 50 arcmin (9 to 21 kpc in deprojected distance) from the center of M33. Some of the questions we hope to answer are: what are the star formation and chemical enrichment histories of the disk and field halo stars? How far does the disk extend from the center of M33? At what distance does the halo begin to dominate over the disk? Answers to questions such as these are vital to a complete understanding of star formation and galactic structure.


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