8764(  1) - 12/30/99 13:06  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8764
                                                       Version: 1
                                                       Check-in Date: 30-Dec-1999
                                                                      12:32:58

1.Proposal Title:
Archival Search for a White Dwarf Dark Matter Component via WFPC2 Proper Motion
Measurements
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2. Proposal For  3. Cycle
AR               9
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4. Investigators
                                                                                     Contact?
    PI: Arlin Crotts                      Columbia University
   CoI: Dr. Geza Gyuk                     University of California, San Diego           N
   CoI: Dr. Lawrence Widrow               Queens University                             N
   CoI: Mr. Robert Uglesich               Columbia University                           N

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5. Abstract

We propose searching for proper motions of faint blue objects in a previously well
sampled field. Such objects have been recently detected in the HDF and are suggested
to be old halo white dwarfs (Ibata et al. 1999). If this identification is correct,
and the implied density persists, a major portion of the dark matter in galactic
halos will have been found. A dominant baryonic component in dark halos has dramatic
consequences for fields spanning much of astronomy and astrophysics. Theories of
structure and galactic formation would have to be revised, while our understanding
of stellar birth would need to account to the drastically different IMF required to
produce halo white dwarfs. In addition the baryon and metallicity budgets of the
universe would be profoundly effected. With the addition of the previously analysed
HDF, our selection of a field at high galactic latitude would also allow us to begin
examining the spatial distribution of the new population. A true halo population
should be clearly distinguishable from a thick disk-type distribution via the
directions and magnitudes of the proper motions as a function of (l, b). Since these
objects are faint (V ~ 28.5) and require high precision astrometry only HST can
study them. We choose the best archival field to evaluate this approach, with no
additional cost in HST time.
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                                                8764(  1) - 12/30/99 13:06  - [  2]

            Summary Form for Proposal  8764

  Item                         Used in this proposal
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  Proposal Category            AR
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