Spitzer AGN candidates in CDFN

We study the multi-wavelength properties of this sample and compare the AGNs selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the >=2.5sigma detection level.

Most of the remaining galaxies are likely to host AGNs that are heavily obscured in the X-ray. Because the power-law selection requires the AGNs to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the Spitzer-detected AGN population at high luminosities and redshifts. The high 24um detection fraction also points to a luminous population.