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An explanation for the soft X-ray excess in active galactic nuclei
Authors:J Crummy  A C Fabian  L Gallo  R R Ross
Institution:Institute of Astronomy, Madingley Road, Cambridge CB3 0HA;Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany;Physics Department, College of the Holy Cross, Worcester, MA 01610, USA
Abstract:We present a large sample of type 1 active galactic nuclei (AGN) spectra taken with XMM–Newton , and fit them with both the conventional model (a power law and blackbody) and the relativistically blurred photoionized disc reflection model of Ross & Fabian. We find that the disc reflection model is a better fit. The disc reflection model successfully reproduces the continuum shape, including the soft excess, of all the sources. The model also reproduces many features that would conventionally be interpreted as absorption edges. We are able to use the model to infer the properties of the sources, specifically that the majority of black holes in the sample are strongly rotating, and that there is a deficit in sources with an inclination >70°. We conclude that the disc reflection model is an important tool in the study of AGN X-ray spectra.
Keywords:accretion  accretion discs  galaxies: active  X-rays: galaxies
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