Hot Accretion with Conduction: Spontaneous Thermal Outflows

Abstract

Motivated by the low collisionality of gas accreted onto black holes in Sgr Aand other nearby galactic nuclei, we study a family of two-dimensional advective accretion solutions with thermal conduction. While we only impose global inflow,the accretionflow 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 signoftheBernoulliconstantdoesnotdiscriminate betweeninflowingandoutflowingregions.Ourparametersurvey 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 � . As the magnitude of conduction is increased, out- flows canadopt aconical geometry,pureinflow solutionsemerge, andthelimit oftwo-dimensional nonrotatingBondi- like solutions is eventually reached. These results confirm that radiatively inefficient, hot accretion flows have a hydrodynamic propensity to generate bipolar thermal outflows. Subject headingg accretion, accretion disks — black hole physics — conduction — hydrodynamics Online material: color figures