z {approx} 7 GALAXY CANDIDATES FROM NICMOS OBSERVATIONS OVER THE HDF-SOUTH AND THE CDF-SOUTH AND HDF-NORTH GOODS FIELDS
- Astronomy Department, University of California, Santa Cruz, CA 95064 (United States)
- Carnegie Observatories, Pasadena, CA 91101 (United States)
- Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden (Netherlands)
- School of Physics and Astronomy, University of c Nottingham, Nottingham, NG72RD (United Kingdom)
- Herzberg Institute of Astrophysics, Victoria, BCV9E2E7 (Canada)
- Department of Astronomy, Yale University, New Haven, CT 06520 (United States)
- Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)
- Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
We use {approx}88 arcmin{sup 2} of deep ({approx}>26.5 mag at 5{sigma}) NICMOS data over the two GOODS fields and the HDF-South to conduct a search for bright z {approx}> 7 galaxy candidates. This search takes advantage of an efficient preselection over 58 arcmin{sup 2} of NICMOS H{sub 160}-band data where only plausible z {approx}> 7 candidates are followed up with NICMOS J{sub 110}-band observations. {approx}248 arcmin{sup 2} of deep ground-based near-infrared data ({approx}>25.5 mag, 5{sigma}) are also considered in the search. In total, we report 15 z{sub 850}-dropout candidates over this area-7 of which are new to these search fields. Two possible z {approx} 9 J{sub 110}-dropout candidates are also found, but seem unlikely to correspond to z {approx} 9 galaxies (given the estimated contamination levels). The present z {approx} 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 {approx} 7 selection is {approx}24%. Through careful simulations, the effective volume available to our z {approx}> 7 selections is estimated and used to establish constraints on the volume density of luminous (L*{sub z{sub ={sub 3}}}, or {approx}-21 mag) galaxies from these searches. We find that the volume density of luminous star-forming galaxies at z {approx} 7 is 13{sup +8}{sub -5} times lower than at z {approx} 4 and >25 times lower (1{sigma}) at z {approx} 9 than at z {approx} 4. This is the most stringent constraint yet available on the volume density of {approx}>L*{sub z{sub ={sub 3}}} galaxies at z {approx} 9. The present wide-area, multi-field search limits cosmic variance to {approx}<20%. The evolution we find at the bright end of the UV LF 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 {approx} 7 z{sub 850}-dropout sample (18 candidates) identified from all NICMOS observations to date (over the two GOODS fields, the HUDF, galaxy clusters).
- OSTI ID:
- 21476696
- Journal Information:
- Astrophysical Journal, Vol. 725, Issue 2; Other Information: DOI: 10.1088/0004-637X/725/2/1587; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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