Speaker
Description
Axion couplings to photons could induce photon-axion conversion in the presence of magnetic fields in the Universe. This conversion could impact various cosmic distance measurements, such as luminosity distances to type Ia supernovae and angular distances to galaxy clusters, in different ways. In this talk we consider different combinations of the most up-to-date distance measurements to constrain the axion-photon coupling. Employing the conservative cell magnetic field model for the magnetic fields in the intergalactic medium (IGM) and ignoring the conversion in the intracluster medium (ICM), we find the upper bounds on axion-photon couplings to be around $5\times 10^{−12}~(\mathrm{nG}/B)~\sqrt{\mathrm{Mpc}/s}~\mathrm{GeV}^{−1}$ for axion masses below $10^{−13}~\mathrm{eV}$, where B is the strength of the IGM magnetic field, and s is the comoving size of the magnetic domains. When including the conversion in the ICM, the upper bound is lowered and could reach $5\times 10^{−13}~\mathrm{GeV}^{−1}$ for masses below $5 \times 10^{−12}~\mathrm{eV}$. While this stronger bound depends on the ICM modeling, it is independent of the strength of the IGM magnetic field.
