The integrated Sachs-Wolfe effect: a confirmation for the case of dark energy

Abstract

We review in these proceedings the status of the integrated Sachs‐Wolfe (ISW) effect measurements, our current data and some cosmological applications. After briefly describing how the ISW effect is produced, we will show how we have measured it by cross‐correlating in real space the cosmic microwave background (CMB) data from the WMAP satellite with six galaxy catalogues spanning a redshift range 0<z<2. By generating random realisations of the maps with a Monte Carlo technique, we estimated the significance of the combined detection to be >4σ when fitting a single amplitude. If we interpret this detection to be due to the ISW effect, we can conclude that this is one more confirmation that the Universe is presently undergoing a transition to a dark energy phase, independently agreeing with the results from other observations. We then discuss how these data, together with other tests of structure formation such as galaxy counts, weak lensing and peculiar velocities, are a promising tool to break the degeneracies which exist at the background level between different theories of gravity. We work in detail the cases of the Dvali‐Gabadadze‐Porrati braneworld model and the class of f(R) theories, finding no evidence for a departure from general relativity.