The rest-frame optical properties of SCUBA galaxies

Abstract

We present optical and near-infrared photometry for a sample of 96 dusty, far-infraredluminous galaxies. We have precise spectroscopic redshifts for all these galaxies, yielding a median redshift of = 2.2. The majority, 78, are submillimeter-detected galaxies lying at z = 0.23.6, while the remaining 18 are optically faint Jy radio galaxies at z = 0.93.4 that 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 with local samples of dusty, luminous galaxies. We confirm that spectroscopically identified far-infraredluminous galaxies at z > 1 display a wide variety in their opticalnear-infrared and near-infrared 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 rest-frame optical passbands than comparable samples of UV-selected star-forming galaxies at similar redshifts. Archival Hubble Space Telescope 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 near-infrared Hubble diagram for far-infraredluminous galaxies. This shows that this population is typically fainter than high-luminosity radio galaxies at similar redshifts and exhibits significantly more scatter in their K-band magnitudes. The rest-frame optical luminosities of the far-infraredluminous 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-infraredluminous sources identify star formation and active galactic nucleusfueling events in the early life of massive galaxies in the universe.