10672(  2) - 06/21/05 08:23  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 10672

Version: 2    Check-in Time: 21-Jun-2005 12:22:05

Title
Calibrating Post-Main-Sequence Evolution in the Upper HRD
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Type             Cycle     Parallel Pointing Tolerance
AR               14        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Claus Leitherer               Space Telescope Science Institute
   CoI: Dr. Rupali Chandar                Space Telescope Science Institute             N

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Abstract

Over its 10 years of Costar-enabled lifetime, HST has accumulated a rich legacy of
resolved stellar photometry in nearby galaxies. The resulting color-magnitude
diagrams of the massive stellar populations rival those obtained from the ground for
the Magellanic Clouds. We propose to analyze multiband imagery of 19 nearby galaxies
to derive densely populated upper color-magnitude and Hertzsprung Russell diagrams
(HRD). This study generalizes previous attempts done for the Magellanic Clouds to
lower metallicities. Our primary scientific goal is a comparison with stellar
evolution and evolutionary synthesis models, identification of mismatches, and an
empirical recalibration. All major models are known to fail to reproduce both the
colors and the population densities of metal-poor red supergiants in the HRD. We
intend to use average HRDs at low metallicity for a recalibration of the stellar
temperatures and lifetimes in stellar evolution models of red supergiants. Lacking
such a recalibration, current synthesis models are inadequate for modeling metal-
poor star-forming and starburst regions containing cool, evolved stars.
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                                                10672(  2) - 06/21/05 08:23  - [  2]

            Summary Form for Proposal  10672

  Item                         Used in this proposal
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  Proposal Category            AR
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