Using the Bullet Cluster as a Gravitational Telescope to Study z~7 Lyman Break Galaxies

Abstract

We use imaging obtained with the Hubble Space Telescope Wide Field Camera 3 to search for z_850 dropouts at z~7 and J_110 dropouts at z~9 lensed by the Bullet Cluster. In total we find 10 z_850 dropouts in our 8.27 arcmin^2 field. Using magnification maps from a combined weak and strong lensing mass reconstruction of the Bullet Cluster and correcting for estimated completeness levels, we calculate the surface density and luminosity function of our z_850 dropouts as a function of intrinsic (accounting for magnification) magnitude. We find results consistent with published blank field surveys, despite using much shallower data, and demonstrate the effectiveness of cluster surveys in the search for z~7 galaxies.

12 pages, 2 tables, 9 figures. Accepted for publication in ApJ. V3: two new figures, improved calculation of intrinsic counts, better organization, added references; main results did not change significantly