Exploring various corona geometries and their emissivity profiles

Abstract

The differences in emissivity profiles produced by various corona geometries are explored via general relativistic ray tracing simulations in order to better understand the inner disc region of active galactic nuclei. Emissivity profiles produced by point sources are distinguishable from those produced by cylindrical slabs and spheroidal coronae, but are indistinguishable from profiles produced by conical geometries, requiring an analysis of reflection fraction to differentiate them. Beamed point and beamed conical sources exhibit differences most evident in the reflection fraction. For point sources a relationship for the measured reflection fraction with source height and velocity is determined. Simulating spectra from the emissivity profiles produced by the various geometries produce distinguishable differences that do not exceed 15 per cent in the most extreme cases. Emissivity profiles are found to be useful in distinguishing point source and extended geometries given high quality spectral data of extreme, bright sources over long exposure times.