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 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 AGNs 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.