Next Talk: November 25
Abstract:
The growth of supermassive black holes can be traced via the observed
luminosities of active galactic nuclei, but for most sources the line
of sight is blocked by gas and dust. Commonly used luminosity
indicators (e.g., X-ray continuum, optical line emission) are often
attenuated by several orders of magnitude, and it is difficult to
accurately estimate extinction corrections. The [O IV] 26 micron line
is more robust because it probes high-ionization gas and suffers
little dust attenuation. Using Spitzer measurements of [O IV] for a
complete sample of 90 local Seyfert galaxies, we find that the
luminosity distributions of obscured and unobscured AGNs are
indistinguishable, even though the obscured sources are systematically
fainter in terms of [O III] optical and 2-10 keV X-ray emission. In
addition, as part of of our work to calibrate the relationship between
[O IV] and AGN intrinsic luminosity, we find that even hard (10-200
keV) X-rays are biased tracers, particularly for Compton-thick
sources. This has important implications for the census of black hole
growth from future X-ray surveys.