JWST lensed quasar dark matter survey V: Hints of self-interacting dark matter from 29 quadruply imaged quasars

Abstract

Theories of self-interacting dark matter (SIDM) predict the eventual core collapse of dark matter halos, a process that transforms these structures into extremely efficient gravitational lenses. We present a population-level inference on the abundance of core collapsed halos and subhalos in the mass range $10^6 - 10^{10.7} M_{\odot}$ using 29 quadruply imaged quasars, drawing on the collective lensing signal of many low-mass perturbers. Our structure formation model predicts the abundance of collapsed (sub)halos as a function of halo mass and redshift. We quantify how our results are affected by systematic uncertainties, including the abundance of globular clusters (GCs) and subhalos, and the internal structure of deeply collapsed halos. Our data exhibits a strong preference for core collapsed halos in the lens model, with Bayes factors disfavoring CDM relative to SIDM ranging from 6:1 to 24:1, depending on the assumed properties of the SIDM subhalo and GC populations. Explaining our data without core collapse requires both a GC abundance well above expectations and more subhalos than predicted by $N$-body simulations. These results pose a challenge to the CDM paradigm. We present a particle physics interpretation of these results in a companion paper.