Using available optical and X-ray catalogues of clusters and superclusters of galaxies , we build templates of tSZ emission as they should be detected by the WMAP experiment .
We compute the cross-correlation of our templates with WMAP temperature maps , and interpret our results separately for clusters and for superclusters of galaxies .
For clusters of galaxies , we claim 2-5 \sigma detections in our templates built from BCS ( ) , NORAS ( ) and ( ) catalogues .
In these templates , the typical cluster temperature decrements in WMAP maps are around 15-35 \mu K in the RJ range ( no beam deconvolution applied ) .
Several tests probing the possible influence of foregrounds in our analyses demonstrate that our results are robust against galactic contamination .
On supercluster scales , we detect a diffuse component in the V & W WMAP bands which can not be generated by superclusters in our catalogues ( ) , and which is not present in the clean map of Tegmark , de Oliveira-Costa & Hamilton ( 2003 ) .
Using this clean map , our analyses yield , for Einasto ’ s supercluster catalogues , the following upper limit for the comptonization parameter associated to supercluster scales : y _ { SC } < 2.18 \times 10 ^ { -8 } at the 95 % confidence limit .