9533(  1) - 12/06/01 12:43  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9533
                                                       Version: 1
                                                       Check-in Date: 06-Dec-2001
                                                                      11:46:58

1.Proposal Title:
The Dependence of Environment on the Galaxy Merger Rate
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2. Proposal For  3. Cycle
AR               11
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4. Investigators
                                                                                     Contact?
    PI: Christopher Conselice             Space Telescope Science Institute
   CoI: Dr. Megan Donahue                 Space Telescope Science Institute             N
   CoI: Prof. Matthew Bershady            University of Wisconsin-Madison               N

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5. Abstract

Galaxy mergers drive the evolution of galaxies, yet we have little understanding of
when, where, and how this process occurs. Galaxy merger rates in the richest
clusters and in the field have now been measured out to z ~ 1, although the effect
of environment on this process is not understood at all. We propose to address this
question by using quantitative structural techniques that can identify which
galaxies are undergoing mergers in extant images of high redshift clusters near z ~
0.8. The merger rate in low density areas should increase faster with redshift than
in denser clusters, but the gas fraction in cluster galaxies may increase with
redshift more rapidly. These two effects may compete, thereby making it difficult
for previous studies to determine differences in field and cluster merger rates.
Understanding how the merger rate varies as a function of local number densities in
these clusters will help answer some fundamental questions concerning galaxy
evolution. These include: (i) determining if the morphology-density relationship in
clusters, in place at z ~ 0.5, is driven by galaxy mergers, (ii) if galaxy mergers
identified by eye in previous studies of clusters are actual mergers, or galaxies
losing mass from high-speed galaxy interactions and (iii) disentangling gas-rich and
gas-poor interactions of a given strength in clusters at z ~ 0.8.
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                                                9533(  1) - 12/06/01 12:43  - [  2]

            Summary Form for Proposal  9533

  Item                         Used in this proposal
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  Proposal Category            AR
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