11278(  1) - 03/30/07 11:25  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11278

Version: 1    Check-in Time: 30-Mar-2007 15:24:58       STScI Edit Number: 0

Title
AGN Variability in the GOODS Fields
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Vicki L. Sarajedini           University of Florida
   CoI: Dr. David C. Koo                  University of California - Santa Cruz         N
   CoI: Ms. Alison Klesman                University of Florida                         N
   CoI: Dr. Renbin Yan                    University of California - Berkeley           N

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Abstract

Variability is a proven method to identify intrinsically faint active nuclei in
galaxies found in deep HST surveys. We propose to extend our short-term variability
study of the GOODS fields to include the more recent epochs obtained via supernovae
searchers, increasing the overall time baseline from 6 months to ~2.5 years. Based
on typical AGN lightcurves, we expect to detect ~70% more AGN by including these
more recent epochs. Variable-detected AGN samples complement current X-ray and mid-
IR surveys for AGN by providing unambigous evidence of nuclear activity.
Additionallty, a significant number of variable nuclei are not associated with X-ray
or mid-IR sources and would thus go undetected. With the increased time baseline, we
will be able to construct the structure function (variability amplitude vs. time)
for low-luminosity AGN to z~1. The inclusion of the longer time interval will allow
for better descrimination among the various models describing the nature of AGN
variability. The variability survey will be compared against spectroscopically
selected AGN from the Team Keck Redshift Survey of the GOODS-N and the upcoming
Flamingos-II NIR survey of the GOODS-S. The high-resolution ACS images will be used
to separate the AGN from the host galaxy light and study the morphology, size and
environment of the host galaxy. These studies will address questions concerning the
nature of low-luminosity AGN evolution and variability at z~1.
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