2023MNRAS.522.5434D

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 10⁴ M_⊙ < M_PBH < 10⁶ M_⊙. We obtain an upper limit f_PBH < 0.17 (95 per cent confidence limit). This constraint is independent of all other previously published limits.