NOAO >   Observing Info >   Approved Programs >   2003B-0160

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Proposal Information for 2003B-0160


PI: Taft Armandroff, NOAO, armand@noao.edu
Address: NOAO Gemini Science Center, P.O. Box 26732, Tucson, AZ 85726, USA

CoI: Nelson Caldwell, Smithsonian Astrophysical Observatory
CoI: Gary Da Costa, Australian National University

Title: The Extended Star Formation Histories of M81 Group Dwarf Elliptical Galaxies

Abstract: We propose to use Gemini-North plus NIRI J- and K-band observations to survey five M81 group dwarf elliptical (dE) galaxies for upper asymptotic giant branch (AGB) stars. Such stars are an indicator of the presence of intermediate-age (2 \lesssim age \lesssim 10 Gyr) populations. Our HST/WFPC2 study (in the V and I bands; Caldwell et al., 1998, AJ, 115, 535) has revealed the presence of significant numbers of upper-AGB stars in two M81 group dEs, and we wish to establish if this is a common occurrence by studying other dE members of this group. Near-IR band photometry is required to determine bolometric magnitudes, and therefore age estimates, for any upper-AGB stars found. Our results will provide information on the extended epochs of star formation (if any) in these dwarf ellipticals and will be directly comparable to existing information for Local Group dEs, such as the dwarf companions to the Galaxy and to M31. In this way we will add to the understanding of the factors, which include environment, that govern the star formation history of these galaxies.


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