Infrared color selection of massive galaxies at z > 3
  We introduce a new color-selection technique to identify high-redshift,
massive galaxies that are systematically missed by Lyman-break selection. The
new selection is based on the H_{160} and IRAC 4.5um bands, specifically H -
[4.5] > 2.25 mag. These galaxies, dubbed "HIEROs", include two major
populations that can be separated with an additional J - H color. The
populations are massive and dusty star-forming galaxies at z > 3 (JH-blue) and
extremely dusty galaxies at z < 3 (JH-red). The 350 arcmin^2 of the GOODS-N and
GOODS-S fields with the deepest HST/WFC3 and IRAC data contain 285 HIEROs down
to [4.5] < 24 mag. We focus here primarily on JH-blue (z > 3) HIEROs, which
have a median photometric redshift z ~4.4 and stellar massM_{*}~10^{10.6} Msun,
and are much fainter in the rest-frame UV than similarly massive Lyman-break
galaxies (LBGs). Their star formation rates (SFRs) reaches ~240 Msun yr^{-1}
leading to a specific SFR, sSFR ~4.2 Gyr^{-1}, suggesting that the sSFRs for
massive galaxies continue to grow at z > 2 but at a lower growth rate than from
z=0 to z=2. With a median half-light radius of 2 kpc, including ~20% as compact
as quiescent galaxies at similar redshifts, JH-blue HIEROs represent perfect
star-forming progenitors of the most massive (M_{*} > 10^{11.2} Msun) compact
quiescent galaxies at z ~ 3 and have the right number density. HIEROs make up
~60% of all galaxies with M_{*} > 10^{10.5} Msun identified at z > 3 from their
photometric redshifts. This is five times more than LBGs with nearly no overlap
between the two populations. While HIEROs make up 15-25% of the total SFR
density at z ~ 4-5, they completely dominate the SFR density taking place in
M_{*} >10^{10.5} Msun galaxies, and are therefore crucial to understanding the
very early phase of massive galaxy formation.
