The Sunyaev-Zel'dovich contribution in CMB analyses

The Sunyaev-Zel'dovich (SZ) effect has long been identified as one of the most important secondary effects of the cosmic microwave background. On the one hand, it is a potentially very powerful cosmological probe providing us with additional constraints and, on the other hand, it represents the major source of secondary fluctuations at small angular scales (l >= 1000). We investigate the effects of the SZ modelling in the determination of the cosmological parameters. We explore the consequences of the SZ power spectrum computation by comparing three increasingly complex modelling methods, from a fixed template with an amplitude factor to a calculation including the full cosmological parameter dependency. We study how accurate and unbiased the parameters are when relaxing more and more assumptions on the cosmological model and on the cluster model. A coherent modelling of the SZ power spectrum, including the cosmological dependency, gives better constraints on cosmological parameters, in particular Sigma(8). Methods assuming an SZ template do not bias strongly the cosmological parameters when the cosmology used in the template deviates (slightly) from the reference one. However, all methods are quite sensitive to the intracluster gas distribution and hence require extra information on the clusters to alleviate the induced biases.