Universal profile for cosmic birefringence tomography with radio galaxies

Abstract

We propose a new method to tomographically probe cosmic birefringence using radio galaxies. We show that the redshift evolution of the cosmic birefringence angle induced by a slow-rolling pseudoscalar field, which is a candidate for dynamical dark energy, is independent of the detailed model of the pseudoscalor field. This universal profile evolves predominantly at $z\lesssim 10$. In contrast, if the origin is a dark matter-like pseudscalor field, the resulting birefringence angle tends to be negligible in the low-redshift regime. This new insight provides a strong motivation to independently test the cosmic birefringence using polarized astrophysical sources such as radio galaxies. We find that a sample size of $\text{order}10^5-10^6$ is required to distinguish the profiles, which is achievable with ongoing and upcoming radio surveys such as ASKAP or SKA.

Comments: 6 pages, 2 figures