The Rest-frame Optical Properties of Scuba Galaxies

We present optical and near-infrared photometry for a sample of 96 dusty, far-infrared luminous galaxies. We have precise spectroscopic redshifts for all these galaxies yielding a median redshift of < z>= 2.2. The majority, 78, are submillimeter-detected galaxies lying at z = 0.2–3.6, while the remaining 18 are optically-faint μJy radio galaxies at z = 0.9–3.4 which are proposed to be similarly luminous, dusty galaxies whose dust emission is too hot to be detected in the submillimeter waveband. We compare the photometric and morphological properties of these distant, ultraluminous galaxies to local samples of dusty, luminous galaxies. We confirm that spectroscopicallyidentified far-infrared luminous galaxies at z > 1 display a wide variety in their optical-near-infrared and nearinfrared colors, with only a modest proportion red enough to classify as unusually red. We show that on average luminous, high-redshift dusty galaxies are both brighter and redder in restframe optical passbands than comparable samples of UV-selected star forming galaxies at similar redshifts. Archival HST ACS imaging of 20 of our galaxies demonstrates both morphological indications of mergers and interactions, which may have triggered their luminous far-infrared activity, and structured dust distributions within these galaxies. We derive a nearinfrared Hubble diagram for far-infrared luminous galaxies. This shows that this population is typically fainter than high luminosity radio galaxies at similar redshifts and exhibit significantly more scatter in their K-band magnitudes. The restframe optical luminosities of the far-infrared luminous population are comparable to those of local ultraluminous infrared galaxies, although their far-infrared luminosities are several times higher. The typical extinction-corrected optical luminosity of the high-redshift population, assuming passive evolution, provides a good fit to the bright end of the luminosity function of luminous spheroidal galaxies seen in rich clusters at intermediate redshifts. This adds to the growing body of evidence showing that these high redshift, far-infrared luminous sources identify star-formation and AGN fueling events in the early life of massive galaxies in the Universe. Subject headings: cosmology: observations — infrared: galaxies — galaxies: evolution — galaxies: formation