Universal Profile for Cosmic Birefringence Tomography with Radio Galaxies

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 pseudoscalar field. This universal profile evolves predominantly at z≲10. In contrast, if the origin is a dark matter-like pseudoscalar 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 O10^{5}-10^{6} is required to distinguish the profiles, which is within the scope of ongoing and upcoming radio surveys such as ASKAP or SKA.