AAS 201st Meeting, January, 2003
Session 81. Extragalactic Star Clusters
Poster, Wednesday, January 8, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[81.05] ACS and Keck Observations of Young Star Clusters in the Interacting Galaxy UGC 10214

H. D. Tran, M. Sirianni, H. C. Ford (JHU), G. D. Illingworth (UCO/Lick Obs.), M. Clampin, G. Hartig (STScI), R. H. Becker (UC Davis/LLNL), R. L. White (STScI), F. Bartko (Bartko Sci. & Tech.), N. Benitez, J. P. Blakeslee (JHU), R. Bouwens (UCO/Lick Obs.), T. Broadhurst (Hebrew Univ.), R. Brown, C. Burrows (STScI), E. Cheng (NASA-GSFC), N. Cross, P. D. Feldman (JHU), M. Franx (Leiden Obs.), D. A. Golimowski (JHU), C. Gronwall (Penn State Univ.), L. Infante (Pontificia Univ. Catolica de Chile), R. Kimble (NASA-GSFC), J. Krist (STScI), M. Lesser (Steward Obs.), D. Magee (UCO/Lick Obs.), A. R Martel, Wm. J. McCann, G. R. Meurer (JHU), G. Miley (Leiden Obs.), M. Postman (STScI), P. Rosati (ESO), W. B. Sparks (STScI), Z. Tsvetanov (JHU)

We present the first Advanced Camera for Surveys (ACS) observations of young star clusters in the colliding/merging galaxy UGC 10214. The observations were made as part of the Early Release Observation (ERO) program for the newly installed ACS during service mission SM3B for the Hubble Space Telescope (HST). Many young star clusters can be identified in the tails of UGC 10214, with ages ranging from ~ 3 Myr to 10 Myr. The extreme blue V-I (F606W-F814W) colors of the star clusters found in the tail of UGC 10214 can only be explained if strong emission lines are included with a young stellar population. This has been confirmed by our Keck spectroscopy of some of these bright blue stellar knots. The most luminous and largest of these blue knots has an absolute magnitude of MV = -14.45, with a half-light radius of 161 pc, and if it is a single star cluster, would qualify as a super star cluster (SSC). Alternatively, it could be a superposition of multiple scaled OB associations or clusters. With an estimated age of ~ 4-5 Myr, its derived mass is \lesssim 1.3 \times 106 M\sun. Thus the young stellar knot is unbound and will not evolve into a normal globular cluster. The bright blue clusters and associations in the tail lie at large projected distances from the nucleus and occur at the edges of low surface brightness gaps in the tail, providing strong evidence that the star formation begins in the tail long after it was ejected.

ACS was developed under NASA contract NAS 5-32864, and this research is supported by NASA grant NAG5-7697. We are grateful for an equipment grant from the Sun Microsystems, Inc.

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