8371(  2) - 12/18/98 16:51  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8371
                                                       Version: 2
                                                       Check-in Date: 18-Dec-1998
                                                                      16:49:16

1.Proposal Title:
Near-UV Spectra of Andromeda Globular Clusters Compared to Spectral Calculations
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2. Proposal For  3. Cycle
AR               8
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4. Investigators
                                                                                     Contact?
    PI: Ruth Peterson                     Astrophysical Advances

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5. Abstract

The near-ultraviolet spectrum of an old stellar population offers the best hope for
determining its age and metallicity, since it is dominated by stars near the main-
sequence turnoff. We have begun the first step towards this goal by calculating
spectra from first principles from 2400Angstrom\ to 3200Angstrom\ for late F and
early G stars near the main sequence. The calculations span metallicities 0.1 to 5*
solar, and agree well at the low end with stellar IUE and HST spectra. Here we
propose to compare archival near-UV spectra of four globular clusters in M31 against
theoretical composite spectra to be derived from the grid. Calculated spectra for
stars of various temperature and gravity will be weighted and coadded at each of
several levels of overall metallicity and relative light-element abundance. We will
check the validity of each satisfactory near-UV match against the available color-
magnitude diagram and optical spectroscopy for each cluster. The results should
show, at each cluster metallicity, how accurately age and metallicity may be derived
from near-UV spectra alone and what observational requirements on wavelength
coverage, S/N, and resolution are entailed for extragalactic objects which cannot be
spatially resolved or optically observed.
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  Data Distribution

  Paper Products:  NO
  Media:           ELECTRONIC
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:
  Email:
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                                                8371(  2) - 12/18/98 16:51  - [  2]

            Summary Form for Proposal  8371

  Item                         Used in this proposal
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  Proposal Category            AR
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