  First, we verify that the physical parameters estimated for the four directly
detected gravitational wave (GW) events involving coalescence of binary black
holes (BHs) indeed uphold the second law of BH thermodynamics, strengthening
further the case for BH physics. Non-spherical gravitational collapse leading
to BH formation may entail very high GW luminosities during the final phase of
implosion, reaching non-negligible fraction of Dyson luminosity $\sim c^5/G $.
  Most galaxies harbor supermassive black holes (SMBHs) in their nuclear
regions. Several bright quasars detected at redshifts $\gtrsim$ 6 are powered
by accreting SMBHs of mass $\gtrsim 10^9 M_\odot$ when the universe was only
$\sim 10^9$ yrs old. We posit that creation of SMBHs occurs due to collapse (on
dynamical time scales $\sim 10^8$ yrs) of ultra-light bosonic dark matter (DM)
particles that have undergone Bose-Einstein condensation. Furthermore,
oscillations in DM Bose-Einstein condensates (BECs) triggered by tidal forces
in interacting galaxies can lead to bursts of star formation in the galactic
nuclei because of frequent collisions of gas clouds due to changing
gravitational field.
  We buttress our proposal by first employing simple but tangible physical
arguments, and then by making use of Gross-Pitaevskii equation to study the
formation of rotating SMBHs having mass $\gtrsim 10^9 M_\odot$. We also make
simple estimates of GW amplitude as well as luminosity ensuing from the time
varying configuration of BECs, constituted by the ultra-light dark bosons, and
remark on the possibility of detecting such GWs using Pulsar Timing Arrays.
