The Nature of the Bright Submillimeter Galaxy Population: A Radio-preselected Sample with I > ~25

Deep submillimeter surveys have successfully detected distant, star-forming galaxies, which are enshrouded in vast quantities of dust and emit most of their energy at far-infrared wavelengths. These luminous galaxies are an important constituent of the universal star formation history, and any complete model of galaxy evolution must account for their existence. Although these sources have been tentatively identified with very faint and sometimes very red optical counterparts, their poorly constrained redshift distribution has made their interpretation unclear. In particular, it was not understood if these galaxies had been missed in previous surveys or if they constituted a truly new class of objects, undetectable at other wavelengths. By utilizing a radio selection technique, we have isolated a sample of 20 submillimeter objects representative of the 850 μm population brighter than 5 mJy with z ≲ 3. We show that these galaxies are so heavily dust-obscured that they remain essentially "invisible" to ultraviolet selection. Furthermore, relying on the radio/submillimeter flux density ratio, we estimate their redshift distribution, finding a median of two. These results are inconsistent with the existence of a very high redshift (z > 4) population of primeval galaxies (Lbol > 1012 L☉) contributing substantially to the submillimeter counts. While not a substitute for the thorough follow-up of blank-field submillimeter surveys, our results do shed light on a substantial portion of the luminous submillimeter population with z ≲ 3.