UCLA

We report the discovery of a z ∼ 9 Lyman break galaxy candidate, selected from the NICMOS Parallel Imaging Survey as a J-dropout with J 110 - H160 = 1.7. Spitzer/IRAC photometry reveals that the galaxy has a blue H160 - 3.6 μm color and a spectral break between 3.6 and 4.5 μm. We interpret this break as the Balmer break and derive a best-fit photometric redshift of z ∼ 9. We use Monte Carlo simulations to test the significance of this photometric redshift, and we show that there is a 96% probability of z ≥ 7. We estimate that the lower limit to the comoving number density of such galaxies at z ∼ 9 is ø > 3.8 × 10-6 Mpc-3. If the high redshift of this galaxy is confirmed, this will indicate that the luminous end of the rest-frame UV luminosity function has not evolved substantially from z ∼ 9 to z ∼ 3. Still, some small degeneracy remains between this z ∼ 9 model and models at z ∼ 2-3; deep optical imaging (reaching IAB ∼ 29) can rule out the lower z models. © 2008. The American Astronomical Society. All rights reserved.