Planck 2013 results. XIX. The integrated Sachs-Wolfe effect
Overview & Synopsis
Based on cosmic microwave background (CMB) maps from the 2013 Planck Mission data release, this paper presents the detection of the integrated Sachs-Wolfe (ISW) effect, that is, the correlation between the CMB and large-scale evolving gravitational potentials. The significance of detection ranges from 2 to 4σ, depending on which method is used. We investigated three separate approaches, which essentially cover all previous studies, and also break new ground. (i) We correlated the CMB with the Planck reconstructed gravitational lensing potential (for the first time). This detection was made using the lensing-induced bispectrum between the low-ℓ and high-ℓ temperature anisotropies; the correlation between lensing and the ISW effect has a significance close to 2.5σ. (ii) We cross-correlated with tracers of large-scale structure, which yielded a significance of about 3σ, based on a combination of radio (NVSS) and optical (SDSS) data. (iii) We used aperture photometry on stacked CMB fields at the locations of known large-scale structures, which yielded and confirms a 4σ signal, over a broader spectral range, when using a previously explored catalogue, but shows strong discrepancies in amplitude and scale when compared with expectations. More recent catalogues give more moderate results that range from negligible to 2.5σ at most, but have a more consistent scale and amplitude, the latter being still slightly higher than what is expected from numerical simulations within ΛCMD. Where they can be compared, these measurements are compatible with previous work using data from WMAP, where these scales have been mapped to the limits of cosmic variance. Planck’s broader frequency coverage allows for better foreground cleaning and confirms that the signal is achromatic, which makes it preferable for ISW detection. As a final step we used tracers of large-scale structure to filter the CMB data, from which we present maps of the ISW temperature perturbation. These results provide complementary and independent evidence for the existence of a dark energy component that governs the currently accelerated expansion of the Universe.
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