Constraining Axion-Like Particles (ALPs) using X-ray observations of galaxy clusters.

My Ph.D. project will focus on constraining the parameter space of light Axion-Like Particles (ALPs) using X-ray observations of galaxy clusters.

In the presence of a magnetized plasma, such as that provided by the IntraCluster Medium (ICM) in galaxy clusters, light can convert into ALPs of a given rest-mass, with a specific coupling strength to photons. This will take place if in a favourable location of phase-space, which depends on both these ALPs parameters, as well as several astrophysical parameters, such as the photon energy and the plasma frequency. At X-ray energies, and for a suitable astrophysical environment such as that provided by the ICM of a rich cluster of galaxies, we could expect photon-ALP oscillations to induce spectral distortions on spectra of bright sources whose light travels through the ICM. This can be used to constrain the parameter space of ALPs.

Currently, I am focussing on constraining light ALPs using High Energy Transmission Grating Spectroscopy data of the H1821+643 quasar. This source has redshift 0.3 and the data I am currently working with were taken by the Chandra telescope. In the long-term, my Ph.D. research will focus on studying whether the Athena X-ray telescope, expected to be launched in the next decade, will be able to constrain light ALPs (that is, their parameter space) further.