New star forming galaxies at z ≈ 7 from WFC3 imaging

Abstract

The addition of Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) has led to a dramatic increase in our ability to study the z > 6 Universe. The improvement in the near-infrared (NIR) sensitivity of WFC3 over previous instruments has enabled us to reach apparent magnitudes approaching 29 (AB). This allows us to probe the rest-frame ultraviolet (UV) continuum, redshifted into the NIR at z > 6. Taking advantage of the large optical depths of the intergalactic medium at this redshift, resulting in the Lyman-α break, we use a combination of WFC3 imaging and pre-existing Advanced Camera for Surveys (ACS) imaging to search for z ≈ 7 galaxies over 4 fields in and around Great Observatories Origins Survey (GOODS) South. Our analysis reveals 29 new z ≈ 7 star forming galaxy candidates in addition to 15 preexisting candidates already discovered in these fields. The improved statistics from our doubling of the robust sample of z-drop candidates confirms the previously observed evolution of the bright end of the luminosity function.