Title:  Variable Galaxies Detected with the Hubble Space Telescope



Vicki Sarajedini
University of Florida



Abstract:

I will present recent results from imaging surveys with the HST
WFPC2 to detect and study the properties of variable active galaxies
out to redshifts of ~1.   Of particular importance is the nature and
evolution of low-luminosity AGN (i.e., Seyferts and LINERs),
which become increasingly difficult to observe at high redshifts
as the apparent brightness of the nuclear light becomes fainter
and difficult to disentangle from the host galaxy light.  Using
multi-epoch HST images, we isolate and measure nuclear variablility 
on timescales of 2 to 7 years in the HDF-N and Groth-Westphal Survey
Strip.  Several of the variable galaxies are also X-ray sources
detected with the Chandra and XMM-Newton telescopes.  We estimate
that ~2\% of galaxies in these fields contain variable nuclei.