The Rest‐Frame Optical Properties of SCUBA Galaxies

We present optical and near-IR photometry of 96 dusty, far-IR luminousgalaxies. We have precise spectroscopic redshifts for all these galaxiesyielding a median redshift of z=2.2. The majority, 78, are submm-detectedgalaxies lying at z=0.2-3.6, while the remaining 18 are optically-faint uJyradio galaxies at z=0.9-3.4 which are proposed to be similarly luminous, dustygalaxies whose dust emission is too hot to be detected in the submm. We comparethe photometric and morphological properties of these distant, ultraluminousgalaxies to local samples. We confirm that spectroscopically-identified far-IRluminous galaxies at z>1 display a wide variety in their optical-near-IR andnear-IR colors, with only a modest proportion red enough to classify asunusually red. We show that on average luminous, high-z dusty galaxies are bothbrighter and redder in restframe optical passbands than UV-selectedstar-forming galaxies at similar z. HST ACS imaging of 20 sources demonstratesboth indications of mergers and interactions, which may have triggered theiractivity, and structured dust within these galaxies. We derive a near-IR Hubblediagram for far-IR luminous galaxies, showing that they are typically fainterthan high luminosity radio galaxies at similar z and exhibit more scatter intheir K-band magnitudes. The typical extinction-corrected optical luminosity ofthe high-z population, assuming passive evolution, provides a good fit to thebright end of the luminosity function of luminous spheroidal galaxies seen inrich clusters at z<1. This adds to the growing evidence that these high z,far-infrared luminous sources identify star-formation and AGN fueling events inthe early life of massive galaxies. [Abridged]Comment: published in ApJ, 15 page