The Rest‐Frame Optical Properties of SCUBA Galaxies

Abstract

We present optical and near-IR photometry of 96 dusty, far-IR luminous galaxies. We have precise spectroscopic redshifts for all these galaxies yielding a median redshift of z=2.2. The majority, 78, are submm-detected galaxies lying at z=0.2-3.6, while the remaining 18 are optically-faint uJy 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 submm. We compare the photometric and morphological properties of these distant, ultraluminous galaxies to local samples. We confirm that spectroscopically-identified far-IR luminous galaxies at z>1 display a wide variety in their optical-near-IR and near-IR colors, with only a modest proportion red enough to classify as unusually red. We show that on average luminous, high-z dusty galaxies are both brighter and redder in restframe optical passbands than UV-selected star-forming galaxies at similar z. HST ACS imaging of 20 sources demonstrates both indications of mergers and interactions, which may have triggered their activity, and structured dust within these galaxies. We derive a near-IR Hubble diagram for far-IR luminous galaxies, showing that they are typically fainter than high luminosity radio galaxies at similar z and exhibit more scatter in their K-band magnitudes. The typical extinction-corrected optical luminosity of the high-z 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 z<1. This adds to the growing evidence that these high z, far-infrared luminous sources identify star-formation and AGN fueling events in the early life of massive galaxies. [Abridged]