z ∼ 7 GALAXY CANDIDATES FROM NICMOS OBSERVATIONS OVER THE HDF-SOUTH AND THE CDF-SOUTH AND HDF-NORTH GOODS FIELDS

We use similar to 88 arcmin(2) of deep (greater than or similar to 26.5 mag at 5 sigma) NICMOS data over the two GOODS fields and the HDF-South to conduct a search for bright z greater than or similar to 7 galaxy candidates. This search takes advantage of an efficient preselection over 58 arcmin(2) of NICMOS H-160-band data where only plausible z greater than or similar to 7 candidates are followed up with NICMOS J(110)-band observations. similar to 248 arcmin(2) of deep ground-based near-infrared data (greater than or similar to 25.5 mag, 5s) are also considered in the search. In total, we report 15 z(850)-dropout candidates over this area-7 of which are new to these search fields. Two possible z similar to 9 J(110)-dropout candidates are also found, but seem unlikely to correspond to z similar to 9 galaxies (given the estimated contamination levels). The present z similar to 9 search is used to set upper limits on the prevalence of such sources. Rigorous testing is undertaken to establish the level of contamination of our selections by photometric scatter, low-mass stars, supernovae, and spurious sources. The estimated contamination rate of our z similar to 7 selection is similar to 24%. Through careful simulations, the effective volume available to our z greater than or similar to 7 selections is estimated and used to establish constraints on the volume density of luminous (L*(z=3), or similar to-21 mag) galaxies from these searches. We find that the volume density of luminous star-forming galaxies at z similar to 7 is 13(-5)(+8) times lower than at z similar to 4 and >25 times lower (1 sigma) at z similar to 9 than at z similar to 4. This is the most stringent constraint yet available on the volume density of similar to L*(z=3) galaxies at z similar to 9. The present wide-area, multi-field search limits cosmic variance to less than or similar to 20%. The evolution we find at the bright end of the UVLF is similar to that found from recent Subaru Suprime-Cam, HAWK-I or ERS WFC3/IR searches. The present paper also includes a complete summary of our final z similar to 7 z(850)-dropout sample (18 candidates) identified from all NICMOS observations to date (over the two GOODS fields, the HUDF, galaxy clusters).