Two-point correlation function of wilkinson microwave anisotropy probe 9-yr data

Abstract

Using an optimal estimator for the cosmic microwave background angular power spectra, we compute the temperature two-point correlation function of Wilkinson Microwave Anisotropy Probe 9-yr data at low resolution. Supported by realistic Monte Carlo simulations, we evaluate how such an observed function depends on the Galactic mask. We find that it is more and more consistent with zero (i.e. no correlation) as the Galactic mask is increased. In particular, we estimate that such a behaviour happens very rarely in a cold dark matter model (i.e. <0.01 per cent of the realizations when we adopt a mask, which leaves 46 per cent of observed sky). This is evaluated for the so-called S1/2 estimator, already well known in the literature. Also, we find that its generalization S1 to the whole angular range [0, π] is very unlikely at the <0.04 per cent confidence level for the masks considered, which cover at least ~54 per cent of the sky. © 2013 The Author. Published by Oxford University Press on behalf of the Royal Astronomical Society.