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

Self-interacting dark matter (SIDM) models predict that dark matter halos can eventually undergo core collapse, transforming them into extremely efficient gravitational lenses. This work, part of the JWST lensed quasar dark matter survey, uses 29 quadruply imaged quasars to perform a population-level inference on the abundance of core-collapsed halos and subhalos in the mass range 10^6 to 10^10.7 solar masses, drawing on the collective lensing signal from many low-mass perturbers rather than a single lens.

The analysis relies on a structure formation model that predicts the abundance of collapsed (sub)halos as a function of halo mass and redshift. The authors also quantify how systematic uncertainties affect the result, including the abundance of globular clusters (GCs) and subhalos, and the internal structure of deeply collapsed halos.

The data show a strong preference for core-collapsed halos in the lens model. Bayes factors disfavoring CDM relative to SIDM range from 6:1 to 24:1, depending on assumptions about SIDM subhalo properties and the GC population. Explaining the data without core collapse would require both a globular cluster abundance well above expectations and more subhalos than predicted by N-body simulations.

These findings pose a challenge to the CDM paradigm. The authors present a particle physics interpretation of the results in a companion paper.