From: Kyle Dawson (kdawson@lbl.gov)
Date: Wed Oct 19 2005 - 17:06:06 PDT
Decelerating and Dustfree: Targeting SNe in Very High Redshift Galaxy
Clusters
We present a novel approach to obtaining Type Ia supernovae (SNe Ia) at
very high redshifts (z>1). In a 219 orbit cycle 14 program, we are
using the Advanced Camera for Surveys (ACS) and NICMOS on the Hubble
Space Telescope (HST) to repeatedly observe massive galaxy clusters at
z>1 to find and follow SNe. Clusters of galaxies are known to be
dominated by nearly dust-free early type galaxies. SNe discovered in
these glaxies are expected to have negligible dust extinction, the
largest source of both statistical and systematic uncertainty in SNe
derived distances. In addition, galaxy clusters contain a population of
early type galaxies at a density approximately five times that in the
high redshift field, leading to a much higher rate of detection of SNe
Ia in this well-understood host environment. With 20 scheduled
half-nights on the Subaru telecope as well as multiple nights on the
Keck telescope, we are obtaining spectroscopic confirmation and redshift
of newly discovered SNe and their hosts. This data will significantly
improve supernova constraints of dark energy both in terms of
statistical uncertainty, and perhaps more importantly, of systematic
uncertainty. This sample of more than 20 galaxy clusters is also being
studied for weak lensing, galaxy morphology, and color-magnitude
relationship, as part of an entire program of cluster studies.
This work was supported in part by the Office of Science, US DoE, under
contract DE-AC03-76F00098 and in part by NASA through grants associated
with HST-GO-10496.
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