| Abstract: | Based on CMB maps from the 2013 Planck Mission data release, this paper
presents the detection of the ISW effect, i.e., the correlation between the CMB
and large-scale evolving gravitational potentials. The significance of
detection ranges from 2 to 4 sigma, depending on which method is used. We
investigate three separate approaches, which cover essentially all previous
studies, as well as breaking new ground. (i) Correlation of the CMB with the
Planck reconstructed gravitational lensing potential (for the first time). This
detection is made using the lensing-induced bispectrum; the correlation between
lensing and the ISW effect has a significance close to 2.5 sigma. (ii)
Cross-correlation with tracers of LSS, yielding around 3 sigma significance,
based on a combination of radio (NVSS) and optical (SDSS) data. (iii) Aperture
photometry on stacked CMB fields at the locations of known large-scale
structures, which yields a 4 sigma signal when using a previously explored
catalogue, but shows strong discrepancies in amplitude and scale compared to
expectations. Recent catalogues give more moderate results, ranging from
negligible to 2.5 sigma at most, but with a more consistent scale and
amplitude, the latter being still slightly above what is expected from
numerical simulations within LCMD. Where they can be compared, these
measurements are compatible with previous work using data from WMAP, which had
already mapped these scales to the limits of cosmic variance. Planck’s broader
frequency coverage confirms that the signal is achromatic, bolstering the case
for ISW detection. As a final step we use tracers of large-scale structure to
filter the CMB data, presenting maps of the ISW temperature perturbation. These
results provide complementary and independent evidence for the existence of a
dark energy component that governs the current accelerated expansion of the
Universe. |
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