Funnel wall jets and the nature of the soft X-ray excess

Abstract

The smooth soft X-ray excess seen in many type-1 AGN can be well described by models of absorption in partially ionized material with a large velocity dispersion, often physically interpreted as a radiatively driven accretion disk wind. However, the state-of-the-art XSCORT code, which calculates the photoionized radiative transfer through a differentially outflowing absorber, shows that terminal velocities of order ~0.9c are required in order to reproduce the soft X-ray excess. Such a high outflow velocity rules out UV-line driving, continuum radiation driving, and thermal driving as mechanisms for producing the wind. Entrainment of material by the magnetically driven jet is the only plausible origin of such a high velocity flow, but numerical simulations of jets and associated outflows do not currently show sufficient material at high enough velocities to reproduce the soft X-ray excess. If the soft excess is produced by absorption then it seems more likely that the material is clumpy and/or only partially covers the source rather than forming a continuous outflow.

4 pages, one colour figure. Accepted for Publication in MNRAS Letters