4
$\begingroup$

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?

$\endgroup$
  • 3
    $\begingroup$ Can you clarify what you're asking? If you're asking "Did LIGO detect dark matter?" the answer is no it detected two black holes. If you're asking whether black holes in the size range you mention could be the missing 25% of matter then I don't think we can tell at the moment. $\endgroup$ – John Rennie Mar 23 '16 at 9:01
  • 1
    $\begingroup$ @JohnRennie I suppose I am asking whether DM=BH is a real possibility given the (admittedly limited) figures they quote $\endgroup$ – user56903 Mar 23 '16 at 9:47
  • 1
    $\begingroup$ @DirkBruere it is a hypothesis for what the dark matter is, see MACHOs en.wikipedia.org/wiki/Massive_compact_halo_object . $\endgroup$ – anna v Mar 23 '16 at 10:03
  • $\begingroup$ @annav Yes, but does the LIGO results give credence to the hypothesis. other than not being a disproof? $\endgroup$ – user56903 Mar 23 '16 at 11:02
  • 1
    $\begingroup$ @DirkBruere no, it is no extra evidence for the MACHO hypothesis. Just that the signal is consistent with high probability of being from the merging of two black holes of the respective masses. The masses are within the limits, so there is no inconsistency , but to validation either $\endgroup$ – anna v Mar 23 '16 at 11:22
1
$\begingroup$

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.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy