New polarimetric constraints on axion-like particles

Understand

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations.

• Robust limits are derived from the measured bounds on optical circular polarisation and from the distribution of linear polarisations of quasars.
• As an outlook, this technique can be improved by the observation of objects located behind clusters of galaxies, using upcoming space-borne X-ray polarimeters.