Constraining dark energy with cross-correlated CMB and large scale structure data

We investigate the possibility of constraining dark energy with the integrated Sachs-Wolfe effect recently detected by cross-correlating the Wilkinson Microwave Anisotropy Probe maps with several large scale structure surveys. In agreement with previous works, we found that, under the assumption of a flat universe, the integrated Sachs-Wolfe signal is a promising tool for constraining dark energy. Current available data put weak limits on a constant dark energy equation of state w. We also find no constraints on the dark energy sound speed c(e)(2). For quintessencelike dark energy (c(e)(2)=1) we find w <-0.53, while tighter bounds are possible only if the dark energy is "clustered" (c(e)(2)=0), in such a case -1.94 < w <-0.63 at 2 sigma. Better measurements of the cosmic microwave background-large scale structure correlation will be possible with the next generation of deep redshift surveys. This will provide independent constraints on the dark energy which are alternative to those usually inferred from cosmic microwave background and SN-Ia data.