Hot Accretion With Conduction: Spontaneous Thermal Outflows

Abstract

Motivated by the low-collisionality of gas accreted onto black holes in Sgr A* and other nearby galactic nuclei, we study a family of 2D advective accretion solutions with thermal conduction. While we only impose global inflow, the accretion flow spontaneously develops bipolar outflows. The role of conduction is key in providing the extra degree of freedom (latitudinal energy transport) necessary to launch these rotating thermal outflows. The sign of the Bernoulli constant does not discriminate between inflowing and outflowing regions. Our parameter survey covers mass outflow rates from ~ 0 to 13% of the net inflow rate, outflow velocities from ~0 to 11% of the local Keplerian velocity and outflow opening angles from ~ 0 to 60 degs. As the magnitude of conduction is increased, outflows can adopt a conical geometry, pure inflow solutions emerge, and the limit of 2D non-rotating Bondi-like solutions is eventually reached. These results confirm that radiatively-inefficient, hot accretion flows have a hydrodynamical propensity to generate bipolar thermal outflows.