Reprocessed emission line profiles from dense clouds in geometrically thick accretion engines

The central engines of active galactic nuclei (AGN) contain cold, dense mat erial as well as hot X-ray-emitting gas. The standard paradigm for the engi ne geometry is a cold thin disc sandwiched between hot X-ray coronae. Stron g support for this geometry in Seyferts comes from the study of fluorescent iron line profiles, although the evidence is not ubiquitously airtight. Th e thin disc model of line profiles in AGN and in X-ray binaries should stil l be benchmarked against other plausible possibilities. One proposed altern ative is an engine consisting of dense clouds embedded in an optically thin , geometrically thick X-ray-emitting engine. This model is also motivated b y studies of geometrically thick engines such as advection-dominated accret ion flows (ADAFs). Here we compute the reprocessed iron line profiles from dense clouds embedded in geometrically thick, optically thin X-ray-emitting discs near a Schwarzschild black hole. We consider a range of cloud distri butions and disc solutions, including ADAFs, pure radial infall and bipolar outflows. We find that such models can reproduce line profiles similar to those from geometrically thin, optically thick discs and might help allevia te some of the problems encountered from the latter. Thus, independent of t hin discs, thick disc engines can also exhibit iron line profiles if embedd ed dense clouds can survive long enough to reprocess radiation.