Reprocessing of radiation by multi-phase gas in low-luminosity accretion flows

Abstract

We discuss the role that magnetic fields in low-luminosity accretion flows can play in creating and maintaining a multi-phase medium, and show that small clouds or filaments of dense cold gas can dramatically reprocess the ‘primary’ radiation from tori. In particular, radio emission is suppressed by free-free absorption, and an extra (weak) component appears at optical wavelengths. This is expected to be a common process in various environments in the central regions of active galaxies, such as broad-line regions, accretion disc coronae and jets.