Clusters of galaxies and variation of the fine structure constant. (arXiv:1212.1075v1 [astro-ph.CO])

Clusters of galaxies and variation of the fine structure constant. (arXiv:1212.1075v1 [astro-ph.CO]):
We propose a new method to probe for variations in the fine structure
constant alpha 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 CMB frequency spectrum
through the Sunyaev-Zel'dovich effect. These two physical processes can be
characterized by the integrated Comptonization parameter Y_SZ DA^2 and its
X-ray counterpart, the Y_X 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 alpha, as the ratio of the
two parameters depends on the fine structure constant as alpha^{3.5}. We
determine current constraints from a combination of Planck SZ and XMM-Newton
data, testing different models of variation of alpha. When fitting for a
constant value of alpha, we find that current constraints are at the 1% level,
comparable with current CMB constraints. We discuss strategies for further
improving these constraints by almost an order of magnitude.