Ram Pressure Confinement of the Emission Line Gas and the Associated Radio Emission in AGN’s

Abstract

The inferred high temperature and small size of the broadline emitting clouds in quasars and Seyfert galaxies requires some confining mechanism to prevent rapid dissipation of those clouds in a time much shorter than their dynamical time scale. Ram pressure confinement by a supersonic wind provides such confinement while avoiding the mass budget and dynamical drag problems of a static confining medium. Reasonable limits on the mass outflow in the wind restricts the size of the high density BLR (broad-line region) to the canonical 1 pc. The limited range in observed ionization parameter also follows given that the mass accretion rate is similar to the mass outflow rate. Flat spectrum (L ~ 0.5) radio emission from the BLR is also expected to be produced in the bow shocks around the confined clouds.