Did LIGO detect dark matter?

Question

Which is the title of this preprint They claim that:

We consider the possibility that the black-hole (BH) binary detected by LIGO may be a signature of dark matter. Interestingly enough, there remains a window for masses 10M⊙≲Mbh≲100M⊙ where primordial black holes (PBHs) may constitute the dark matter. If two BHs in a galactic halo pass sufficiently close, they can radiate enough energy in gravitational waves to become gravitationally bound. The bound BHs will then rapidly spiral inward due to emission of gravitational radiation and ultimately merge. Uncertainties in the rate for such events arise from our imprecise knowledge of the phase-space structure of galactic halos on the smallest scales. Still, reasonable estimates span a range that overlaps the 2−53 Gpc−3 yr−1 rate estimated from GW150914, thus raising the possibility that LIGO has detected PBH dark matter.

Has this explanation for dark matter in this mass range been explored previously?

Answer 1

Gravitational micro-lensing has already put a non-trivial limit on the total mass density due to small-to medium sized black holes, but does not so far put one on heavy stellar-mass black holes.

Over time, the accumulated data of the (several) gravitational wave detectors may eventually put a limit on the high-mass MACHO contribution to the total mass density, but one observation does nothing in that direction.

The authors of the preprint have jumped the gun.