A redshift limit for the faint blue galaxy population from deep U band imaging

Abstract

A definitive upper limit for the redshift of the population of faint blue galaxies found in deep imaging surveys is obtained. The U-B(j), and particularly the B(j)-R, colors of these objects show a blueing trend toward fainter magnitudes. A typical galaxy at R = 26 has colors that are only slightly redder than a flat spectrum. For any reasonable Lyman limit break, this constrains 93 percent or more of the galaxies to under z about 3, beyond which the break gets redshifted through the U band. The galaxies appear to be undergoing relatively recent evolution with rest frame spectra that are approximately flat down to the Lyman limit. 23 refs.