10281(  1) - 04/02/04 10:42  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10281
                                                       Version: 1
                                                       Check-in Date: 02-Apr-2004
                                                                      10:42:22

1.Proposal Title:
Evolution of Stars and Stellar Systems. I. The Initial Size Distribution of Clusters
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
AR               13        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. Rupali Chandar                Space Telescope Science Institute
   CoI: Dr. Claus Leitherer               Space Telescope Science Institute             N
   CoI: Dr. Brad C. Whitmore              Space Telescope Science Institute             N

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6. Abstract

There are three fundamental properties which define a star cluster -- age, mass, and
size. While much attention has been focused on the first two parameters,
significantly less is known concerning not only actual cluster sizes and structures,
but the initial distribution of stellar clustering which occurs in different
environments. For example, NGC 1569 has formed three compact, massive young clusters
in the last 10 Myr, while IZw18 appears to have only formed more diffuse, "scaled
up" OB associations (SOBAs). The HST archive now contains sufficient observations of
nearby star-forming galaxies to allow a quantitative measure of the initial
clustering of star formation. We propose to measure the distribution of the physical
scales of cluster formation, from the most compact clusters to diffuse SOBAs in 30
nearby galaxies. Local variations in the star formation rate may manifest themselves
in the fraction of star formation occuring in compact clusters vs. that occurring in
more diffuse OB associations. Because our galaxy sample covers a large range in
environment, mass, and star formation rate density, we will take the next step, and
use our size distributions to place constraints on the processes responsible for
setting the scales of star formation in the local universe. A complementary proposal
aims to study the isolated red supergiant population in nearby star-forming galaxies
(PI: Dr. C. Leitherer).
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                                                10281(  1) - 04/02/04 10:42  - [  2]

            Summary Form for Proposal  10281

  Item                         Used in this proposal
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  Proposal Category            AR
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