Magellan Spectroscopy of AGN Candidates in the COSMOS Field

Abstract

We present spectroscopic redshifts for the first 466 X-ray and radio-selected AGN targets in the 2 deg^2 COSMOS field. Spectra were obtained with the IMACS instrument on the Magellan (Baade) telescope, using the nod-and-shuffle technique. We identify a variety of Type 1 and Type 2 AGN, as well as red galaxies with no emission lines. Our redshift yield is 72% down to i_AB=24, although the yield is >90% for i_AB<22. We expect the completeness to increase as the survey continues. When our survey is complete and additional redshifts from the zCOSMOS project are included, we anticipate ~1100 AGN with redshifts over the entire COSMOS field. Our redshift survey is consistent with an obscured AGN population that peaks at z~0.7, although further work is necessary to disentangle the selection effects.