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Kinematics of Star Clusters in M33: Distinct Populations

Published online by Cambridge University Press:  03 August 2017

Rupali Chandar ,
Luciana Bianchi ,
Holland C. Ford  and
Ata Sarajedini
Rupali Chandar
Affiliation:
Johns Hopkins University, Department of Physics & Astronomy, 3400 N. Charles St., Baltimore, MD 21218 USA
Luciana Bianchi
Affiliation:
Johns Hopkins University, Department of Physics & Astronomy, 3400 N. Charles St., Baltimore, MD 21218 USA
Holland C. Ford
Affiliation:
Johns Hopkins University, Department of Physics & Astronomy, 3400 N. Charles St., Baltimore, MD 21218 USA
Ata Sarajedini
Affiliation:
Department of Astronomy, University of Florida, P. O. Box 112055, Gainesville, FL 32611-2055 USA

Abstract

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We analyse star cluster properties in the nearby spiral galaxy M33, combining our extensive HST WFPC2 photometry and ground-based follow up spectroscopy. These data show that cluster velocity dispersion increases with age. Simulations comparing synthetic disk and halo populations with observations indicate a composite disk/halo system for the old M33 clusters. The best fit fraction of 85 ± 5% halo plus 15 ± 5% disk differs from that found in the Milky Way, where ∼ 30% of the globular clusters are metal rich objects associated with the bulge and/or thick disk. Spectroscopic line indices for a halo subsample (17 objects) reveal an age spread of ∼ 5 — 7 Gyr, and little progression in metal abundance with age. This is consistent with a chaotic formation for a substantial portion of the M33 halo, and also consistent with an accretion origin for a large number of the halo clusters.

Type
Part 1. The Star Clusters of Local Group Galaxies
Information
Symposium - International Astronomical Union , Volume 207: Extragalactic Star Clusters , 2002 , pp. 160 - 162
Copyright
Copyright © Astronomical Society of the Pacific 2002 

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