11253(  1) - 03/30/07 11:09  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11253

Version: 1    Check-in Time: 30-Mar-2007 15:09:03       STScI Edit Number: 0

Title
Sizes and Morphology of z=3.1 Lyman Alpha Emitting Galaxies in the Extended CDF-S
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Eric Gawiser                  Rutgers the State University of New Jersey
   CoI: Dr. Caryl Gronwall                The Pennsylvania State University             N
   CoI: Dr. Robin Ciardullo               The Pennsylvania State University             N
   CoI: Dr. John J. Feldmeier             Youngstown State University                   N
   CoI: Mr. Kevin Schawinski              University of Oxford                          N
   CoI: Dr. Leopoldo Infante              Universidad Catolica de Chile                 N
   CoI: Dr. Paulina Lira                  Universidad de Chile                          N

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Abstract

Lyman Alpha Emitting galaxies (LAEs) seen at high redshift appear to be galaxies in
the act of formation. They are currently the most promising candidates for the
progenitors of typical spiral galaxies like the Milky Way. The LAEs tend to be
younger, lower in mass, and less chemically evolved than the better-studied Lyman
Break Galaxies (LBGs). Wide-field ACS imaging allows us to study the physical
properties of these objects at kpc scales to gain a better understanding of the
interconnected processes of mergers and star formation that play fundamental roles
in galaxy formation. We will use archival ACS images of the Extended Chandra Deep
Field-South from GEMS, GOODS, and UDF to study the size and morphology of our sample
of 162 Lyman Alpha Emitters at z=3.1, 47 of which have confirmed spectroscopic
redshifts. We will perform the identical analysis on a sample of 34
spectroscopically confirmed Lyman Break Galaxies at 2.7<z<3.9 to compare the
physical properties of these two families of high-redshift galaxies. At this
redshift, the ACS F606W and F850LP bands trace the rest-frame ultraviolet radiation
from ongoing star formation. We will determine parametric measures of morphology
(Sersic radii, CAS parameters, Gini coefficient, M20) along with non-parametric
measures (half-light radii, number of star-forming clumps, size and separation of
clumps) to provide critical constraints upon models of galaxy formation. We will use
the objects that lie in the deeper GOODS and UDF regions to model uncertainties in
the GEMS results. We will correct the astrometric zeropoints of the GEMS images and
reproject them to match the standard GOODS/MUSYC pixelization scheme for this field
and will offer these images to the community via the HST archive.
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