Clumpy-gas radiation hydrodynamics: Application to quasar PDS 456

Abstract Based upon clumpy-gas radiation hydrodynamics developed recently, we examine super-Eddington clumpy outflows in active galactic nuclei, using steady purely spherical winds and centrifugal-assisted semi-spherical outflows. Despite the models being quite simple, the dynamical properties of clumps in quasar PDS 456 can be roughly explained. In the clumps-gas two-component fluids, the efficiency of the radiative force acting on clumps is less than unity, compared with that acting on the ambient gas, and becomes smaller as the optical depth is larger. Hence, as for quasar PDS 456 with the Eddington parameter of $\Gamma =1.6$ and the clump speed $u_\infty$ of $0.2\, c$–$0.3\, c$, the optical depth $\tau _{\rm c}$ of clumps must be less than 5. Furthermore, the clumps with $\tau _{\rm c}=1$ would be launched between $7\, r_{\rm S}$ (for $u_\infty =0.3\, c$) and $16\, r_{\rm S}$ (for $u_\infty =0.2\, c$), where $r_{\rm S}$ is the Schwarzschild radius of the central black hole. In addition, the speed of the ambient gaseous matter would be higher than clumps, and would be around $0.3\, c$–$0.4\, c$.