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N. A. Levenson (Univ. Ky.), K. A. Weaver (NASA/GSFC and JHU), T. M. Heckman, J. H. Krolik (JHU), P. T. Zycki (NCAC)
Surveys at all wavelengths are biased against finding strongly obscured active galactic nuclei (AGN), especially at high redshift. Locally, up to half of all Seyfert 2 galaxies are Compton thick, with obscuring column densities that exceed 1024 cm-2, yet even X-ray surveys would fail to classify them correctly using crude techniques such as hardness ratios.
Nearby Seyfert 2 galaxies are relatively bright and allow high spatial resolution measurements. Detailed analysis of their physical conditions and energetic sources provides useful templates of more distant examples where similar investigations are unfeasible. With Chandra X-ray Observatory and Hubble Space Telescope observations of local Seyfert 2 galaxies, we determine the empirical signatures of highly obscured AGN. The physically-motivated diagnostics we develop will help to identify and classify other AGN correctly, even where the quality of observational data is low.
At X-ray wavelengths, we specifically find that contributions from star formation and extranuclear photoionization are usually significant. These effects must be considered in order to to accurately measure the intrinsic luminosity of these AGN and their obscuration.
This work is supported by NASA grant G04-5117 and NSF CAREER award AST-0237291.
The author(s) of this abstract have provided an email address for comments about the abstract: levenson@pa.uky.edu
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.