Evidence for a Buried AGN in an Extremely Bright Dusty Galaxy at z=2

We present preliminary results of a submillimeter spectral line survey of a strongly-lensed dusty star-forming galaxy (DSFG) at z ~ 2, near the peak epoch of cosmic star formation. We use data from the Submillimeter Array (SMA), which recently completed a systems upgrade that substantially increased the instantaneous bandwidth. Focusing on the brightest spectral lines of CO and atomic carbon, we characterize the interstellar medium properties of this galaxy. We find highly excited CO and [CI] emission, and a large [CI] line ratio implies a higher excitation temperature than other extreme high-redshift sources. Based on this evidence, we infer that the source likely hosts a dust-obscured active galactic nucleus (AGN) similar to other well-studied dusty star-forming galaxies (DSFGs).