Zusammenfassung
The remarkable HST datasets from the CANDELS, HUDF09, HUDF12, ERS, and
BORG/HIPPIES programs have allowed us to map out the evolution of the UV LF
from z~10 to z~4. We develop new color criteria that more optimally utilize the
full wavelength coverage from the optical+near-IR observations over our search
fields, while simultaneously minimizing the incompleteness and eliminating
redshift gaps. We have identified 5991, 3391, 940, 598, 225, and 6 galaxy
candidates at z~4, z~5, z~6, z~7, z~8, and z~10, respectively from the ~1000
arcmin**2 area covered by these datasets. The large z~4-8 samples we have
identified in the five CANDELS fields allow us to assess the cosmic variance;
the largest variations are apparent at z>=7. Our new LF determinations at z~4
and z~5 span a 6-mag baseline (-22.5 to -16 AB mag). These determinations agree
well with previous estimates, but the larger samples and the larger volumes
probed here result in a more reliable sampling of >L* galaxies and allow us to
reassess the form of the UV LFs. Our new LF results strengthen our earlier
findings to 4.5 sigma significance for a steeper UV LF at z>4, with alpha
evolving from alpha=-1.64+/-0.04 at z~4 to alpha=-2.06+/-0.12 at z~7. The
observed steepening of the UV LF is consistent with that expected from the
evolution of the halo mass function. With our improved constraints at the
bright end, we find less evolution in the characteristic luminosity M* over the
redshift range z~4 to z~7 consistent with current models; the observed
evolution in the LF is now largely represented by changes in phi*. Even with
the much larger sample of bright galaxies, we find no evidence for the LF
having a non-Schechter-like form at z~4-8. A simple conditional LF model based
on halo growth and a modest evolution in the M/L of halos provides a good
representation of the evolution of the UV LF.
Nutzer