7552(  1) - 12/14/96 01:08  - [  0]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7552
                                                       Version: 1
                                                       Check-in Date: 13-Dec-1996
                                                                      18:23:42

1.Proposal Title:
A Search for Extended Stellar Galactic Halos
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2. Scientific Category   3. Proposal For  4. Cycle
GALAXIES                    AR               7
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5. Investigators
                                                                                     Contact?
    PI: Dennis Zaritsky                   University of California, Santa Cruz

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6. Abstract

Several lines of evidence (ground based observations of NGC 5907; the apparent large
fraction of Galactic dark matter accounted for by MACHOS) suggest that galactic
halos consist primarily of stellar-type objects out to radii of at least several
tens of kpc. Further investigation of this claim is critical in constraining the
properties of dark matter and the nature of galactic halos. We propose to use HST
archival images of random edge-on field spiral galaxies in the F814W filter to trace
the extended stellar light around disk galaxies. HST data provides two key
advantages for this study: (1) the background surface brightness at 8000Angstrom\ is
about 2 mag fainter than for ground based images; and (2) the contamination by
foreground stars is effectively eliminated because HST resolution enables one to
study relatively distant galaxies, which have fewer superposed stars because of
their small angular extents. Both of these advantages will enable us to map the
extended light to the unprecedented level of 28 \mg2 at 8000Angstrom. If the data
and model of Sackett Etal (1994) are correct, we will map the extended emission, and
hence the stellar halo, to a vertical distance above and below the plane that is at
least twice as large as ever before.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
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                                                7552(  1) - 12/14/96 01:08  - [  1]

            Summary Form for Proposal  7552

  Item                         Used in this proposal
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  Proposal Category            AR
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  Scientific Category          GALAXIES
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