11281(  1) - 03/30/07 11:27  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11281

Version: 1    Check-in Time: 30-Mar-2007 15:27:04       STScI Edit Number: 0

Title
The Durations of Starbursts in Blue Compact Galaxies
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Evan D. Skillman              University of Minnesota - Twin Cities
   CoI: Ms. Kristen McQuinn               University of Minnesota - Twin Cities         N
   CoI: Dr. Sebastian Hidalgo             University of Minnesota - Twin Cities         N
   CoI: Dr. Andrew A. Cole                University of Minnesota - Twin Cities         N
   CoI: Mr. Dan Weisz                     University of Minnesota - Twin Cities         N
   CoI: Dr. John M. Cannon                Wesleyan University                           N
   CoI: Dr. Andrew Dolphin                Raytheon Technical Services Company           N

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Abstract

The starburst phenomenon is a very important phase of galaxy evolution, and
especially so for dwarf galaxies. The duration of the burst is important because it
impacts both the evolution of the galaxy itself and the evolution of the local
environment external to the galaxy. In addition to the physical conditions and
evolution of the galaxy, the length of the burst and degree of "burstiness" affects
the detectability of low luminosity galaxies. There is no consensus in the
literature on the typical duration of a burst in a dwarf galaxy; some studies favor
durations of roughly 5 Myr, and others roughly 100 Myr. We propose to resolve this
discrepancy. The HST archive contains high quality imaging observations of a number
of nearby starbursts in dwarf galaxies (often called Blue Compact Dwarf galaxies or
BCDs). However, these have been obtained through a number of diverse investigations
focusing on a wide variety of science questions. Here we propose a systematic,
uniform analysis of these nearby BCDs that will produce star formation histories
(SFHs) with a primary goal of determining the duration of the burst. Specifically,
we will: (1) reduce the photometry in a uniform manner using programs optimized for
HST observations, (2) use two of the most sophisticated programs available to derive
optimal star formation histories from the resulting color-magnitude diagrams,
including modeling of the effects of differential extinction, and (3) compare these
results and conduct Monte Carlo simulations in order to securely quantify the
uncertainties in the derived star formation rates. This approach will allow us, for
the first time, to compare the results for a significant sample in a uniform and
unbiased way, and thus, draw unambiguous conclusions regarding the duration of
starbursts in BCDs.
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