New star-forming galaxies at z ≈ 7 from Wide Field Camera Three imaging

Abstract

The addition of Wide Field Camera Three on the Hubble Space Telescope 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 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 imaging to search for z ≈ 7 galaxies over four fields in and around Great Observatories Origins Survey-South (GOODS-S). Our analysis reveals 29 new z ≈ 7 star-forming galaxy candidates in addition to 15 pre-existing 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.