Data from the Hubble Ultra Deep Field and its associated
parallel fields constitute the deepest optical and infrared
looks ever taken of the universe. Not only do these fields
provide unprecedented measures of the number of faint
galaxies at z~4-6, but these data permit meaningful
constraints on early galaxy formation out to redshifts as
high as 12. Impressively, these data have already allowed us
to obtain samples of candidate z~7-8 objects and to set some
upper limits on the number of bright objects at earlier
redshifts (z~8-12). Early studies point towards there being
a deficit of objects at the bright end relative to lower
redshifts and towards galaxies having a much steeper faint
end slope. This suggests that the majority of galaxies were
much smaller at early times, as expected in hierarchical
scenarios of galaxy formation.
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