Supermassive Black Holes from self-gravitating Bose-Einstein Condensates comprised of Ultra-light Bosonic Dark Matter

Abstract

Observed active galactic nuclei at redshifts $\gtrsim 6$ suggest that supermassive black holes (SMBHs) had formed early on. Accretion of matter onto remnants of Population III stars leading to SMBHs is a very slow process, and therefore, such models encounter difficulties in explaining quasars detected at $ z \gtrsim 6$. In this paper, we invoke collapse of dark bosonic halo matter, existing initially in self-gravitating Bose-Einstein condensate (BEC) phase, to lead to formation of SMBH. Making use of Gross-Pitaevskii equation and employing a Gaussian trial wavefunction, we determine the time dependence of its parameters and thereby, track the time evolution of the wavefunction. If the condensate, made up of identical dark bosons of mass $m$, collapses to form a black hole of mass $M_{eff}$ as soon as the former's effective size shrinks below the corresponding Schwarzschild radius, a simple inequality $ m \ M_{eff} \gtrsim 0.64 \ m^2_{Pl} $ can be derived, that ensues from a competition between attractive self-gravity and quantum repulsion arising due to uncertainty principle. We show that formation of SMBHs takes place on dynamical time scales $\sim 10^8$ yrs. Existence of ultra-light ($m \sim 10^{-23} \ \mbox{eV}$) dark bosons not only can lead to SMBHs of mass $\sim 10^{12} \ M_\odot$ at $ z > 6$ but also such particles can masquerade both as dark matter as well as dark energy. Discovery of aligned radio-jets in the ELAIS-N1 GMRT deep field leads us to make simple estimates to demonstrate that vortices of a rotating BEC that collapse to form black holes can give rise to SMBHs with aligned spins on scales exceeding cluster size length scales, each with angular momentum $J \lesssim 3.6 \ n_W \frac {G M^2} {c}$, where $n_W$ and $M$ are the winding number and mass of a vortex, respectively.