While the deepest pencil-beam near-IR survey suggested that the Universe was too young to build up many luminous galaxies by z ~ 7--8 (Bouwens & Illingworth 2006), there is also evidenc indicating the contrary. It is now known that some galaxies with stellar masses of M>1e10 Msun were already in place by z ~ 6--7, which strongly suggests that their progenitors should be significantly more luminous, and hence detectable in deep, wide-field near-IR surveys (Yan et al. 2006). As galaxies at such a high redshift should manifest themselves as "dropouts" from the optical, we have carried out a very wide-field, deep near-IR survey in the GOODS fields to search for z-band dropouts as candidates of galaxies at z > 7. In total, six promising candidates have been found in ~ 300 sq. arcmin to J_AB ~ 24.5 mag (corresponding to restframe M(UV) < -22.5 mag at z ~ 7). By constrast, the galaxy luminosity function (LF) suggested in BI06 would predict at most 3--5 galaxies over the entire 2-pi sky at this brightness level. Here we propose to observe these candidates with NIC3 in F110W and F160W to further investigate their nature. If any of these candidates are indeed at z > 7, the result will lead to a completely new picture of star formation in the early universe. If none of our candidates are consistent with being at z > 7, then the depth and area of our near-IR survey (from which the candidates are drawn) will let us set a very stringent upper limit on the bright end of the galaxy LF at those redshift. As a result, our program will still be able to provide new clues about the processes of early galaxy formation, such as their dust contents and their merging time scale (Yan et al. 2006).

This project will use NIC3 to image a few luminous z>7 candidates in the F110W and the F160W filters. Six independent fields will be observed. Four of these fields are in the general direction of the HDF-N, while the remaining two are in the CDF-S. Each field will be observed for 2 orbits in F110W and 2 orbits in F160W. COSMOLOGY 12 false 0 0 false false false false false SUPPORTED GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 12 37 2.0000 +62 17 18.00 J2000 GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 12 37 0.0000 +62 17 18.00 J2000 GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 12 37 0.0000 +62 17 18.00 J2000 GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 12 37 0.0000 +62 17 18.00 J2000 GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 03 32 33.0000 -27 42 0.00 J2000 GALAXY HIGH REDSHIFT GALAXY PROTOGALAXY J(AB) ~ 24.5 J2000 03 32 33.0000 -27 42 0.00 J2000 NIC3 Imaging No No F110W NIC3 Imaging No No F160W NIC3 Imaging No No F110W NIC3 Imaging No No F160W NIC3 Imaging No No F110W NIC3 Imaging No No F160W NIC3 Imaging No No F110W NIC3 Imaging No No F160W NIC3 Imaging No No F110W NIC3 Imaging No No F160W NIC3 Imaging No No F110W NIC3 Imaging No No F160W WFPC2 Imaging No F300W WFPC2 Imaging No F300W WFPC2 Imaging No F300W WFPC2 Imaging No F300W 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