Marusa Bradac

Title: Dark Matter and First Galaxies Light Up

Abstract: The cluster of galaxies 1E0657-56 has been the subject of intense
research in the last few years.  This system is remarkably well-suited
to addressing outstanding issues in both cosmology and fundamental
physics. It is one of the hottest and most luminous X-ray clusters
known, and is unique in being a major supersonic cluster merger
occurring nearly in the plane of the sky, earning it the nickname "the
Bullet Cluster". The newest HST/WFC3 data has revealed further
interesting properties of this cluster. We have also studied a new
Bullet-like cluster, MACSJ0025-1222. Allthough it does not contain a
low-entropy, high density hydrodynamical `bullet,' this cluster
exhibits many similar properties to the Bullet Cluster.

The advent of Wide Field Camera 3 (WFC3) on HST enabled us to detect
galaxies at z>7. They are likely beacons of the epoch of reionization,
which marked the end of the so-called ``Dark Ages'' and signified the
transformation of the universe from opaque to transparent. Clusters of
galaxies, when used as cosmic telescopes, can greatly simplify the
task of studying and finding these galaxies.  In this talk I will
present the new results we have on using the Bullet cluster as a
`cosmic telescope' to explore the Universe in its infancy