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E.N. Dueñas (NASA Goddard Inst. for Space Studies), K.J. Mighell (NOAO)
We present our preliminary analysis of archival Hubble Space Telescope WFPC2 observations in the F555W (V) and F814W (I) filters of the metal-poor globular cluster Arp 2 in the nearby Sagittarius dwarf spheroidal galaxy. The deep V vs. (V-I) color-magnitude diagram reaches 3.5 magnitudes below the main sequence turnoff with a signal-to-noise ratio of 10 or greater in both filters; it also features a well-defined subgiant branch as well as a few blue stragglers. The upper red giant branch is not analyzed due to photometric saturation. Most previous studies of Arp 2 analyzed the ground-based BV observations of Buonanno et al. (1995) or the ground-based VI observations of Sarajedini & Layden (1997). Buonanno et al. found that Arp 2 is a metal-poor, intermediate age cluster, while Layden & Sarajedini (2000) determined that it is coeval with other ancient Galactic globular clusters, e.g. 13.1 ±0.9 Gyr. We have analyzed our space-based observations with the Yonsei-Yale (Y2) isochrones of Yi et al. (2001) and present evidence that confirms the Layden & Sarajedini's ancient-age hypothesis for Arp 2.
Dueñas was supported, in part, by awards to South Carolina State University from NASA/MU-SPIN (NCC 5-534) and NASA/OSS (NAG 5-10145), and the NOAO/KPNO REU Program, funded by the National Science Foundation. Mighell was supported by a grant from the National Aeronautics and Space Administration (NASA), S-67046-F, awarded by the Long-Term Space Astrophysics program of NASA's Office of Space Science.
The author(s) of this abstract have provided an email address for comments about the abstract: eduenas@giss.nasa.gov
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.