Rapid growth of black holes accompanied with hot or warm outflows exposed to anisotropic super-Eddington radiation

We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto a black hole (BH) with a mass of 10^3≤ M_ BH/M_⊙≲ 10^6 in order to study rapid growth of BHs in the early Universe. For spherically symmetric flows, hyper-Eddington accretion onto the BH from outside the Bondi radius can occur unimpeded by radiation feedback only when the BH mass is higher than ≃ 10^4 M_⊙(n_∞/10^5 cm^-3)^-1(T_∞/10^4 K)^3/2, where n_∞ and T_∞ are the density and temperature of ambient gas. Here, we study the properties of accretion flows exposed to anisotropic radiation from a nuclear accretion disk with a luminosity higher than the Eddington value (L_ Edd) due to collimation toward the bipolar directions. We find that, unlike the spherically symmetric case, even less massive BHs with M_ BH < 10^4 M_⊙ can be fed by surrounding gas at high accretion rates of ≳ L_ Edd/c^2 through the equatorial plane, while ionized regions expand to the polar directions producing hot outflows with T∼ 10^5K. For more massive BHs with M_ BH≳ 5× 10^5 M_⊙, neutral gas through the equatorial plane totally covers the central radiating region due to the non-radial gas motions, and thus the emergent radiation in all directions is blocked. Because of efficient recombination by hydrogen, the entire flow results in neutral and warm gas with T ≃ 8000 K . The central BH is fed through the equator at the averaged rate of ∼ 5× 10^4 L_ Edd/c^2, which corresponds to ∼ 50 % of the inflow rate from the Bondi radius. Moreover, radiation momentum absorbed by neutral hydrogen produces warm outflows toward the bipolar directions at ∼ 30 % of the BH feeding rate and with a typical velocity of ≃ 50 km s^-1.