Clusters of galaxies and variation of the fine structure constant.

We propose a new method to probe for variations in the fine structure constant a using clusters of galaxies, opening up a window on a new redshift range for such constraints. Hot clusters shine in the x-ray mainly due to bremsstrahlung, while they leave an imprint on the cosmic microwave background (CMB) frequency spectrum through the Sunyaev-Zel'dovich effect. These two physical processes can be characterized by the integrated Comptonization parameter YSZD2A and its x-ray counterpart, the Yx parameter. The ratio of these two quantities is expected to be constant from numerical simulations and current observations. We show that this fact can be exploited to constrain a, as the ratio of the two parameters depends on the fine structure constant as ∝ α3,5. We determine current constraints from a combination of Planck SZ and XMM-Newton data, testing different models of variation of a. When fitting for a constant value of α, we find that current constraints are at the 0.8% level, comparable with current CMB bounds. We discuss strategies for further improving these constraints by at least a factor ~3. [ABSTRACT FROM AUTHOR]