In order to find the most extreme dust-hidden high-redshift galaxies , we select 196 extremely red objects in the K _ { S } and IRAC bands ( KIEROs , [ K _ { s } -4.5 \mu m ] _ { AB } > 1.6 ) in the 0.06 deg ^ { 2 } GOODS-N region .
This selection avoids the Balmer breaks of galactic spectra at z < 4 and picks up red galaxies with strong dust extinction .
The photometric redshifts of KIEROs are between 1.5 and 5 , with \sim 70 \% at z \sim 2 –4 .
KIEROs are very massive , with M _ { \star } \sim 10 ^ { 10 } – 10 ^ { 12 } M _ { \sun } .
They are optically faint and usually can not be picked out by the Lyman break selection .
On the other hand , the KIERO selection includes approximately half of the known millimeter and submillimeter galaxies in the GOODS-N. Stacking analyses in the radio , millimeter , and submillimeter all show that KIEROs are much more luminous than average 4.5 \mu m selected galaxies .
Interestingly , the stacked fluxes for ACS-undetected KIEROs in these wavebands are 2.5–5 times larger than those for ACS-detected KIEROs .
With the stacked radio fluxes and the local radio–FIR correlation , we derive mean infrared luminosities of 2– 7 \times 10 ^ { 12 } L _ { \sun } and mean star formation rates of 300-1200 M _ { \sun } yr ^ { -1 } for KIEROs with redshifts .
We do not find evidence of a significant subpopulation of passive KIEROs .
The large stellar masses and star formation rates imply that KIEROs are z > 2 massive galaxies in rapid formation .
Our results show that a large sample of dusty ultraluminous sources can be selected in this way and that a large fraction of high-redshift star formation is hidden by dust .