Magellan spectroscopy of AGN candidates in the COSMOS field

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 AGNs, as well as red galaxies with no emission lines. Our red-shift yield is 72% down to i(AB) 24, although the yield is > 90% for iAB < 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 similar to 1100 AGNs with redshifts over the entire COSMOS field. Our redshift survey is consistent with an obscured AGN population that peaks at z similar to 0: 7, although further work is necessary to disentangle the selection effects.