  We investigate the properties of quiescent and star-forming galaxy
populations to z~2 with purely photometric data, employing a novel rest-frame
color selection technique. From the UKIDSS Ultra-Deep Survey Data Release 1,
with matched optical and mid-IR photometry taken from the Subaru XMM Deep
Survey and Spitzer Wide-Area Infrared Extragalactic Survey respectively, we
construct a K-selected galaxy catalog and calculate photometric redshifts.
Excluding stars, objects with uncertain z_phot solutions, those that fall in
bad or incomplete survey regions, and those for which reliable rest-frame
colors could not be derived, 30108 galaxies with K<22.4 (AB) and z<2.5 remain.
The galaxies in this sample are found to occupy two distinct populations in the
rest-frame U-V vs. V-J color space: a clump of red, quiescent galaxies
(analogous to the red sequence) and a track of star-forming galaxies extending
from blue to red U-V colors. This bimodal behavior is seen up to z~2. Due to a
combination of measurement errors and passive evolution, the color-color
diagram is not suitable to distinguish the galaxy bimodality at z>2 for this
sample, but we show that MIPS 24um data suggest that a significant population
of quiescent galaxies exists even at these higher redshifts. At z=1-2, the most
luminous objects in the sample are divided roughly equally between star-forming
and quiescent galaxies, while at lower redshifts most of the brightest galaxies
are quiescent. Moreover, quiescent galaxies at these redshifts are clustered
more strongly than those actively forming stars, indicating that galaxies with
early-quenched star formation may occupy more massive host dark matter halos.
This suggests that the end of star formation is associated with, and perhaps
brought about by, a mechanism related to halo mass.
