AAS 207th Meeting, 8-12 January 2006
Session 157 The Universe at High Redshift
Oral, Wednesday, 2:00-3:30pm, January 11, 2006, Maryland

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[157.05] Galaxies at z~7-11: Evolution of the Star Formation Rate Density

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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