2009ApJ...700.1878R

We compare [O IV] 25.89 µm emission line luminosities with very hard (10-200 keV) X-rays from Swift, INTEGRAL, and BeppoSAX for a complete sample of 89 Seyferts from the Revised Shapley-Ames sample. Using Seyfert 1s, we calibrate [O IV] as a measure of active galactic nucleus (AGN) intrinsic luminosity, for particular use in high-obscuration environments. With this calibration, we measure the average decrement in 14-195 keV X-ray to [O IV] luminosity ratio for Seyfert 2s compared to type 1s. We find a decrement of 3.1±0.8 for Seyfert 2s, and a decrement of 5.0±2.7 for known Compton-thick Seyfert 2s. These decrements imply column densities of approximately log N_H= 24.6/cm2 and 24.7/cm2, respectively. Thus, we infer that the average Seyfert 2 is more highly obscured and intrinsically more luminous than would be inferred even from the very hard X-rays. We demonstrate two applications of the hard X-ray to [O IV] ratio. For the extremely obscured NGC 1068, we measure a column density of log N_H= 25.3-25.4/cm2. Finally, by comparing [O IV] luminosities to total infrared luminosities for 12 bright ultraluminous infrared galaxies, we find that four have substantial AGN contributions.