8767(  1) - 12/30/99 13:07  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8767
                                                       Version: 1
                                                       Check-in Date: 30-Dec-1999
                                                                      12:33:18

1.Proposal Title:
Evolution of 1200 Field E/S0 Galaxies to z = 1
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2. Proposal For  3. Cycle
AR               9
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4. Investigators
                                                                                     Contact?
    PI: Myungshin Im                      University of California
                                          Observatories/Lick Observatory
   CoI: Prof. David C. Koo                University of California                      N
                                          Observatories/Lick Observatory
   CoI: Dr. Luc Simard                    University of California                      N
                                          Observatories/Lick Observatory
   CoI: Prof. Sandra M. Faber             University of California                      N
                                          Observatories/Lick Observatory
   CoI: Prof. Puragra Guhathakurta        University of California                      N
                                          Observatories/Lick Observatory
   CoI: Dr. Christopher Willmer           University of California                      N
                                          Observatories/Lick Observatory

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5. Abstract

The evolution of field E/S0 galaxies, especially their number density, is in debate.
Theoretical models based on hierarchical structure formation predict that a
significant fraction of present day E/S0's are formed at z < 1 via merging. This is
in sharp contrast to the so-called ``monolithic collapse'' model which predicts the
coeval formation of E/S0's at high redshift (z >> 1). Current observational
constraints on the evolution of field E/S0's are controversial, mainly because of
the lack of a sample large enough to provide statistically significant limits. From
the HST Archive, we have identified 230 WFPC2 fields at high Galactic latitude which
have V and I imaging of sufficient depth for morphological identification of E/S0's
to I = 22. In these fields, we estimate that there will be ~ 1200-1400 normal,
luminous, field E/S0's with I < 22, z < 1 and z_med ~ 0.5, enough to provide
significant improvement in the number statistics over previous studies. This large
sample of E/S0 galaxies will constrain : i) the number density evolution of field
E/S0's at z < 1 to an accuracy of better than 10\ ii) the luminosity evolution of
field E/S0's since z=1; and iii) the cosmological parameters. Knowing the number
density should settle whether merging since z=1 can have been a major process in the
formation of E/S0's.
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                                                8767(  1) - 12/30/99 13:07  - [  2]

            Summary Form for Proposal  8767

  Item                         Used in this proposal
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  Proposal Category            AR
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