Bright Strongly Lensed Galaxies at Redshift z~ 6-7 behind the Clusters
  Abell 1703 and CL0024+161
  We report on the discovery of three bright, strongly-lensed objects behind
Abell 1703 and CL0024+16 from a dropout search over 25 square arcminutes of
deep NICMOS data, with deep ACS optical coverage. They are undetected in the
deep ACS images below 8500 A and have clear detections in the J and H bands.
Fits to the ACS, NICMOS and IRAC data yield robust photometric redshifts in the
range z~6-7 and largely rule out the possibility that they are low-redshift
interlopers. All three objects are extended, and resolved into a pair of bright
knots. The bright i-band dropout in Abell 1703 has an H-band AB magnitude of
23.9, which makes it one of the brightest known galaxy candidates at z>5.5. Our
model fits suggest a young, massive galaxy only ~ 60 million years old with a
mass of ~ 1E10 solar mass. The dropout galaxy candidates behind CL0024+16 are
separated by 2.5" (~ 2 kpc in the source plane), and have H-band AB magnitudes
of 25.0 and 25.6. Lensing models of CL0024+16 suggest that the objects have
comparable intrinsic magnitudes of AB ~ 27.3, approximately one magnitude
fainter than L* at z~6.5. Their similar redshifts, spectral energy
distribution, and luminosities, coupled with their very close proximity on the
sky, suggest that they are spatially associated, and plausibly are physically
bound. Combining this sample with two previously reported, similarly magnified
galaxy candidates at z~6-8, we find that complex systems with dual nuclei may
be a common feature of high-redshift galaxies.
