8350(  2) - 12/18/98 16:41  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8350
                                                       Version: 2
                                                       Check-in Date: 18-Dec-1998
                                                                      16:39:27

1.Proposal Title:
A SEARCH FOR INTERGALACTIC STARS IN THE LOCAL GROUP
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2. Proposal For  3. Cycle
AR               8
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4. Investigators
                                                                                     Contact?
    PI: Bart Wakker                       University of Wisconsin-Madison
   CoI: Prof. Joel Bregman                University of Michigan                        N

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5. Abstract

A profound change in our picture of the Local Group has been suggested by Blitz et
al.\ (1998), who argue that dex11 M(sun)\ of HI resides in a long filament between
the Milky Way and M 31, which they identify with the HI high-velocity clouds (HVCs).
Since many HVCs are known to contain heavy elements (with a metallicity of >0.01
times solar), a critical test of the model is to find the evolved stars within the
population that produced these heavy elements. We propose to search for these stars.
Since the model of Blitz et al.\ (1998) predicts HVC distances of >100 kpc, the
stars will be faint (V>24). However, we show that they can be found using starcounts
on WFPC2 images, provided that the space density exceeds ~1/1000 that in the solar
neighborhood, Detecting intergalactic stars in the HI filament would allow a
determination of the distance to the HVCs, and establish the presence of a
completely new component of the Local Group. A negative result would allow stringent
limits to be set on the number of intergalactic stars and on models for HVCs.
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  Data Distribution

  Paper Products:  NO
  Media:           ELECTRONIC
  Blocking Factor: 10
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                                                8350(  2) - 12/18/98 16:41  - [  2]

            Summary Form for Proposal  8350

  Item                         Used in this proposal
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  Proposal Category            AR
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