7981(  1) - 04/16/98 14:05  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7981
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:03:23

1.Proposal Title:
The Concentrations and Tidal Radii of Globular Clusters in Virgo Ellipticals
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Steve Zepf                        Yale University
   CoI: Charles Bailyn                    Yale University                               N

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5. Abstract

We propose to use archival WFPC2 images to constrain the concentration and the tidal
radii of globular clusters around Virgo ellipticals. These parameters are sensitive
probes of the dynamical state of globular clusters. However, WPFC2 programs to date
have only measured half-light profiles based an assumed form of the density profile,
even though it is feasible to constrain both the concentration and tidal radius
independently. Therefore, our program aims to use the large number of archival WFPC2
pointings in the direction of M87 and other Virgo ellipticals to determine the
structural parameters of globular clusters in these galaxies. In particular, we will
use the tidal radii in conjunction with other estimates of the potential well of the
galaxy such as X-ray data and stellar absorption lines, to constrain the mass
profile of the galaxy and the globular cluster orbits. For the concentration, we
will test for correlations with the position of the globular cluster within its host
galaxy, as found for the Galactic globular cluster system. Moreover, this database
will be invaluable for understanding the very large number of low-mass x-ray
binaries (LMXRBs) expected to be discovered in these systems by AXAF. M87 is an
excellent place to test for the relationship of LMXRBs to globular cluster
properties because the very large number of clusters will overcome the small number
statistics of Galactic studies.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
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                                                7981(  1) - 04/16/98 14:05  - [  2]

            Summary Form for Proposal  7981

  Item                         Used in this proposal
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  Proposal Category            AR
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