Subaru Imaging and Spectroscopy of Globular Cluster Candidates around M82

Abstract

We carried out a search for globular clusters in M82 by taking advantage of the relatively high resolution imaging and deep spectroscopic capabilities provided by the Faint Object Camera And Spectograph (FOCAS) on the Subaru Telescope. Since M82 is a late-type galaxy, its globular cluster system provides a basis for comparison with the globular cluster system of our Galaxy or that of M31. The archetypal starburst galaxy M82 also constitutes an ideal target for studying the relation between galaxy interactions, starbursts, and globular cluster formation. First, we performed an imaging survey to pick up globular cluster candidates using the color-magnitude selection method. Follow-up spectroscopic observations were carried out for 29 globular cluster candidates using the multi-object spectroscopic mode of FOCAS. In the central 6′ diameter region of M82, we found two bona fide globular clusters and three young star clusters in our first attempt at optical searching for globular clusters in M82. The estimated age of young star clusters is ≲1 Gyr, which is consistent with or lower than the age derived by infrared photometry. Two bona fide globular clusters should have formed at the epoch of M82's formation. Some of the young star clusters identified in M82 are likely to have been produced during the tidal-interaction episode with M81. © 2005. The american astronomical society. All rights reserved.