9950(  1) - 04/04/03 10:33  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9950
                                                       Version: 1
                                                       Check-in Date: 04-Apr-2003
                                                                      10:32:42

1.Proposal Title:
Optimization of the Tip of the Red Giant Branch Distance Estimator
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Edward Shaya                      Raytheon Technical Services Company
   CoI: Dr. R. Tully                      University of Hawaii                          N
   CoI: Dr. Shoko Sakai                   University of California - Los Angeles        N

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5. Abstract

There are bountiful reasons why it would be wonderful to have a dense grid of
galaxies with precision distances. The ability of HST to resolve stars deep enough
to probe Pop II in nearby galaxies provides the means. The luminosity of the Tip of
the Red Giant Branch (TRGB) in I band is a standard candle with small dispersion.
Already over 100 galaxies have been observed with HST and ultimately several hundred
will probably be observed. Distances can be accumulated at an efficient rate of 1
orbit per galaxy. The resultant dense grid of objects placed in 3D space out to 8
Mpc will provide key information on the amplitude of peculiar motions, the radial
domain of bound groups, the clustering and morphological segregation properties of
galaxies, and the incidence of extreme dwarf galaxies. These investigators are
particularly interested in issues to do with the distribution of matter and the
implications of the apparent very low random velocities indicated by the existing
data. Low random velocities may be a manifestation of the dominance of vacuum energy
over gravity and detailed measurements of velocities may set tight constraints on
cosmological parameters. The exploitation of these exciting possibilities requires a
deeper understanding of the TRGB methodology to make it more accurate and free of
bias.
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                                                9950(  1) - 04/04/03 10:33  - [  2]

            Summary Form for Proposal  9950

  Item                         Used in this proposal
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  Proposal Category            AR
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