Paper detail

A WISE measurement of the ISW effect

The Integrated Sachs-Wolfe effect (ISW) measures the decay of the gravitational potential due to cosmic acceleration and is thus a direct probe of Dark Energy. In some of the earlier studies, the amplitude of the ISW effect was found to be in tension with the predictions of the standard $Λ$CDM model. We measure the cross-power of galaxies and AGN from the WISE mission with CMB temperature data from WMAP9 in order to provide an independent measurement of the ISW amplitude. Cross-correlations with the recently released Planck lensing potential maps are used to calibrate the bias and contamination fraction of the sources, thus avoiding systematic effects that could be present when using auto-spectra to measure bias. We find an amplitude of the cross-power of $\mathcal{A} = 1.24\pm 0.47$ from the galaxies and $\mathcal{A} = 0.88 \pm 0.74$ from the AGN, fully consistent with the $Λ$CDM prediction of $\mathcal{A} =1$. The ISW measurement signal-to-noise ratio is 2.7 and 1.2 respectively, giving a combined significance close to $3 σ$. Comparing the amplitudes of the galaxy and AGN cross-correlations, which arise from different redshifts, we find no evidence for redshift evolution in Dark Energy properties, consistent with a Cosmological Constant.