Deep 2 micron imaging of the sky - Evidence for a new extragalactic population

We have obtained the first deep images of high Galactic latitude sky at 2 microns. These images reach a 1σ detection limit of 21. 9 mag arcsec^-2^ at K, about 1/20, 000 of the sky level. A total of 10 arcmin²^ of the sky was imaged. Of particular interest are two extended objects with K magnitudes of about 17 and R-K colors of about 5. These objects occupy a region of the color-magnitude diagram that is separate from the locus of normal galaxies and should not be occupied by large numbers of normal galaxies at any redshift. We suggest that these may be high-redshift galaxies (z > 6) which are in a luminous star-forming phase. Additionally, we have located a group of objects at K = 18 which are not detected at R and have R-K colors greater than 5. These may be additional members of the class of objects described above, or they may be weakly evolved elliptical galaxies at z = 1-1. 5.