Expanding the Search for Galaxies at z ~ 7-10 with New NICMOS Parallel Fields

June 2009 • 2009ApJ...697.1128H

Authors • Henry, Alaina L. • Siana, Brian • Malkan, Matthew A. • Ashby, Matthew L. N. • Bridge, Carrie R. • Chary, Ranga-Ram • Colbert, James W. • Giavalisco, Mauro • Teplitz, Harry I. • McCarthy, Patrick J.

Abstract • We have carried out a search for galaxies at z ~ 7-10 in ~14.4 arcmin² of new NICMOS parallel imaging taken in the Great Observatories Origins Deep Survey (5.9 arcmin²), the Cosmic Origins Survey (7.2 arcmin²), and SSA22 (1.3 arcmin²). These images reach 5σ sensitivities of J ₁₁₀ = 26.0-27.5 (AB), and combined they increase the amount of deep near-infrared data by more than 60% in fields where the investment in deep optical data has already been made. We find no z > 7 candidates in our survey area, consistent with the Bouwens et al. measurements at z ~ 7 and 9 (over 23 arcmin²), which predict 0.7 galaxies at z ~ 7 and <0.03 galaxies at z ~ 9. We estimate that 10%-20% of z > 7 galaxies are missed by this survey, due to incompleteness from foreground contamination by faint sources. For the case of luminosity evolution, assuming a Schecter parameterization with a typical phi* = 10^-3 Mpc^-3, we find M*> - 20.0 for z ~ 7 and M*> - 20.7 for z ~ 9 (68% confidence). This suggests that the downward luminosity evolution of Lyman break galaxies continues to z ~ 7, although our result is marginally consistent with the z ~ 6 luminosity function of Bouwens et al. In addition, we present newly acquired deep MMT/Megacam imaging of the z ~ 9 candidate JD2325+1433, first presented in Henry et al. The resulting weak but significant detection at i' indicates that this galaxy is most likely an interloper at z ~ 2.7.

This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. These observations are associated with proposals 10872, 11236, and 11188. This work is also based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.

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IPAC Authors
(alphabetical)

Ranga-Ram Chary

Senior Scientist

James Colbert

Associate Scientist

Harry Teplitz

Senior Scientist