Strong lensing constraints on primordial black holes as a dark matter candidate

Dark matter could comprise, at least in part, primordial black holes (PBHs). To test this hypothesis, we present an approach to constrain the PBH mass (M-PBH) and mass fraction (f(PBH)) from the flux ratios of quadruply imaged quasars. Our approach uses an approximate Bayesian computation forward modelling technique to directly sample the posterior distribution of M-PBH and f(PBH), while marginalizing over the subhalo mass function amplitude, spatial distribution, and the size of the lensed source. We apply our method to 11 quadruply imaged quasars and derive a new constraint on the intermediate-mass area of PBH parameter space 10(4) M-circle dot < M-PBH < 10(6) M-circle dot. We obtain an upper limit f(PBH) < 0.17 (95 per cent confidence limit). This constraint is independent of all other previously published limits.

Automated summary

Researchers use Bayesian methods to constrain the mass and mass fraction of primordial black holes (PBHs) using the flux ratios of quadruply imaged quasars. They find that the mass of PBHs ranges from 10^4 to 10^6 solar masses, with an upper limit on the mass fraction of 0.17.