The OPTX Project: Optical Spectroscopy And X-ray Properties of Obscured and Unobscured AGNs

Type Conference Paper
Names Laura Trouille, A. Barger, L. Cowie, R. Mushotzky, Y. Yang
Conference Name American Astronomical Society, AAS Meeting #215, #353.03
Volume 42
Pages 536
Date January 1, 2010
Short Title The OPTX Project
Library Catalog NASA ADS
Abstract In order to understand the evolution of Active Galactic Nuclei, it is essential that we use a physically motivated classification scheme. Using a uniformly selected and highly spectroscopically complete sample of Chandra X-ray sources (the OPTX sample), we confirm that one cannot use X-ray spectral classifications and optical spectral classifications equivalently. We also show that there is not a one-to-one correspondence between X-ray spectral type and the neutral hydrogen opacity of the source. Until a better understanding is reached for how the X-ray and optical classifications relate to the obscuration of the central engine, the use of a mixed classification scheme can only complicate the interpretation of X-ray AGN samples. On the basis of this study, we advocate the adoption of a pure optical classification scheme for studying AGN with low signal-to-noise X-ray spectra. However if high quality X-ray spectra are available, they form an equally valid method of categorizing the objects. We also compare the completeness in AGN selection using X-ray versus optical emission line ratio diagnostic diagrams. We confirm that we miss AGNs in our X-ray selected sample that can be picked up by optical diagnostic diagrams. Conversely, there are X-ray AGNs that lie in the star formation region of these diagrams that we cannot find with this technique. We discuss the effect of this incompleteness on the shape and evolution of X-ray and [OIII] AGN luminosity functions. L. Trouille gratefully acknowledges support from a National Science Foundation Graduate Research Fellowship and a Wisconsin Space Grant Consortium Graduate Fellowship Award while working on this Ph.D. thesis work.
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