2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6764We 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 (θ> 4 deg) yields significant detections of the Integrated Sachs-Wolfe (ISW) effect and provides a new estimate of dark-energy in the universe, Ω_Λ=0.69-0.86 (2 σrange). In addition, the correlated signal on small angles (θ<1 deg) reveals the imprint left by hot intra-cluster gas in the CMB photons: the thermal Sunyaev-Zeldovich (SZ) effect7 pages. Invited talk at XVth Rencontres de Blois (France): "Physical Cosmology", June 2003. References addedAstrophysicstext