2009ApJ...697.1128H

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 J₁₁₀= 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 φ* = 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.