NOAO >   Observing Info >   Approved Programs >   2004B-0378

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Proposal Information for 2004B-0378


PI: Heather Morrison, Case Western Reserve University, heather@vegemite.cwru.edu
Address: Astronomy Department, 10900 Euclid Avenue, Cleveland, OH 44106, USA

CoI: Paul Harding, Case Western Reserve University

Title: M31's surprising globular cluster system: JHK photometry

Abstract: Recent discoveries have shown that the M31 globular cluster system is very different from the Milky Way's. In particular, accurate velocity measurements have shown that some 40% of globulars projected on the M31 disk have the kinematics of a \bf thin disk. This discovery has important implications for our understanding of the early formation of large galaxy disks and of M31's merger history: if the globular clusters are as ancient as the Milky Way's, M31 had a large disk in place at an early epoch. As part of a major project to obtain a consistent and high-quality dataset on all M31 globular clusters brighter than K_0=15, we are applying here for 2.1m/SQIID time to obtain accurate JHK photometry for these clusters. Currently, JHK photometry is available for less than half the sample and comes from several sources - the \bf best data from recent studies disagrees at the 0.2 mag. level for all but a few bright clusters. This photometry, combined with accurate UBVRI photometry, will be used to obtain accurate reddening estimates for all clusters. Adding high S/N spectral data will allow estimates of the ages and metallicities of the clusters. We also plan to compare the disk and non disk cluster luminosity functions.


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