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

TL;DR

This paper introduces a Bayesian modeling approach to constrain the mass and abundance of primordial black holes as dark matter candidates using flux ratios from quadruply imaged quasars, providing new independent limits.

Contribution

The authors develop an ABC forward modeling method to directly estimate PBH parameters from lensing data, marginalizing over various astrophysical uncertainties, and apply it to real quasar observations.

Findings

Derived a new upper limit on PBH fraction: less than 0.17 at 95% confidence.

Constrained PBH mass range to between 10^4 and 10^6 solar masses.

Provided constraints that are independent of previous limits.

Abstract

Dark matter could comprise, at least in part, primordial black holes (PBH). To test this hypothesis, we present an approach to constrain the PBH mass ($M_{\rm{PBH}}$) and mass fraction ($f_{\rm{PBH}}$) from the flux ratios of quadruply imaged quasars. Our approach uses an approximate Bayesian computation (ABC) forward modeling technique to directly sample the posterior distribution of $M_{\rm{PBH}}$ and $f_{\rm{PBH}}$, 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 $M$_{\odot}<M_{\rm{PBH}}<10^6$M$_\odot$. We obtain an upper limit $f_{\mathrm{PBH}}<0.17$ (95\% C.L.). This constraint is independent of all other previously published limits.