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R.J. Bouwens, G.D. Illingworth (UC Santa Cruz)
Our understanding of the evolution of the UV Luminosity Function and star formation rate density is now quite mature to z~6, 0.9 Gyr after recombination. A recent compilation of z~6 galaxies by our group contained ~500 objects and allowed for a robust determination of the LF to luminosities as faint as 0.04 L*. Relative to z~3 LFs, we find significant evidence for evolution from z~6. At z~6, the characteristic luminosity is only half that at z~3, supporting the idea that galaxies built up through hierarchical processes. Extending this to even higher redshifts (z>6) in the reionization epoch has been difficult due to limited number of statistically-representative samples with sizeable membership. Only modest numbers of such objects have been detected at z>6 (~5 z-dropouts - z~7-8 objects - in the Hubble UDF). Significant limits have also been placed at z~10 using over 800 orbits of deep NICMOS data. But the situation is improving as a result of new deep HST data. For example, three deep search fields being obtained over the HUDF and its two NICMOS parallel fields have point source sensitivities down to ~28.3 AB mag (~0.2L*) in both the optical and infrared. In this talk, we will describe the z~7 and z~10 samples we are able to compile from a comprehensive set of deep HST ACS+NICMOS fields, compare them with expectations from z~6, and comment on the evolution in the UV LF at these early times.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.