Axion field tomography: cosmic birefringence from the epochs of recombination and reionization

When coupled to electromagnetism through a Chern-Simons interaction, axion-like particles (ALP) produce a rotation of the plane of linear polarization known as cosmic birefringence (CB). As CB depends on the evolution of the ALP field during the flight of photons, the cosmic microwave background (CMB) photons emitted during reionization might experience a different rotation than those emitted during recombination. Recent measurements from small angular scale CMB polarization anisotropies hint at a βᵣec≈0.3^∘ CB angle from the recombination epoch. Here, we combine large and small angular scale CMB polarization data to simultaneously measure instrumental miscalibration angles and the CB rotation from both epochs, deriving preliminary |βᵣeio| <4.55 ^∘ ($68%$ CL) constraints on the CB angle from the reionization epoch through the use of $EE$ and $BB$ information.