The Formation of Supermassive Black Holes at Early Universe

The high-redshift universe is now the frontier of modern astronomy, and is the key object for current and near-future telescopes. The high-redshift quasars put a tight constraint on existing BH growth model, as it is challenging to form a 10¹⁰ M_⊙ BH at z∼6.

In this work, we relax the widely-adopted Salpeter BH growth model, to consider a more realistic path. We consider the variation in the mass and angular momentum orientation of gas supply (i.e. through ∊_L and n), as well as the change in accretion mode (hot versus cold). Moreover, the conventionally considered BH spin impact on the radiative efficiency ∊_M is also taken into account. Our key results can be summarized as follows. Firstly, sufficient gas supply (larger in ∊_L) is obviously a key factor to make the BH grow efficiently. Also, The BH spin (a_*), through the radiative efficiency ∊_M, has a dominant impact on the BH growth, i.e., those high-redshift quasars with M_BH > 10¹⁰ M_⊙ should be formed in a chaotic gas supply situation, where the angular momentum orientation of the gas is random. Finally, through analyzing the most realistic accretion model, we find that the only existing model of seed BH is through the direct collapse, driven by either dynamical processes or thermodynamics