Cross-correlating the Microwave Sky with Galaxy Surveys

We present results for the cross-correlation between the WMAP 1st-year cosmic microwave background (CMB) anisotropy data and optical galaxy surveys: the APM and SDSS DR1 catalogs. Our measurement of a positive CMB-galaxy correlation on large angles (\theta > 4 deg) yields significant detections of the Integrated Sachs-Wolfe (ISW) effect and provides a new estimate of dark-energy in the universe, \Omega_\Lambda=0.69-0.86 (2 \sigma range). In addition, the correlated signal on small angles (\theta<1 deg) reveals the imprint left by hot intra-cluster gas in the CMB photons: the thermal Sunyaev-Zeldovich (SZ) effect