10642(  1) - 04/05/05 12:13  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10642
                                                       Version: 1
                                                       Check-in Date: 05-Apr-2005
                                                                      16:13:02

1.Proposal Title:
Measurements of Surface Brightness Fluctuations Gradients in Normal and Peculiar
Early-type Galaxies
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
AR               14        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. Michele Cantiello             INAF, Osservatorio Astronomico di Teramo
   CoI: Prof. Enzo Brocato                INAF, Osservatorio Astronomico di Teramo      N
   CoI: Dr. John Paul Blakeslee           The Johns Hopkins University                  Y
   CoI: Dr. Gabriella Raimondo            INAF, Osservatorio Astronomico di Teramo      N
   CoI: Prof. Massimo Capaccioli          INAF, Osservatorio Astronomico di             N
                                          Capodimonte

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6. Abstract

Surface Brightness Fluctuations (SBF) provide a highly promising tool for tracing
the properties of unresolved stellar populations in external galaxies. We propose to
measure radial SBF gradients in archival ACS/F814W images of early-type galaxies and
correlate these gradients with their broadband colors. As we have demonstrated in
preliminary investigations, the exceptional imaging capabilities of ACS now makes it
possible to measure highly accurate SBF gradients in a large sample of galaxies.
Comparison of our preliminary results with new stellar population models shows that
SBF, and SBF gradients with radius, complement the information provided by classical
photometry, helping to break the usual age/metallicity degeneracy. The proposed
archival research would more than double the number of galaxies with measured SBF
gradients, including the addition of shell galaxies, which likely have had
interesting and complex star formation histories. In addition, we will measure near-
IR SBF properties in a subsample of these galaxies that also have NICMOS imaging,
providing substantially more leverage for breaking the age/metallicity degeneracy.
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                                                10642(  1) - 04/05/05 12:13  - [  2]

            Summary Form for Proposal  10642

  Item                         Used in this proposal
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  Proposal Category            AR
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