USING THE KINEMATIC SUNYAEV-ZELDOVICH EFFECT TO DETERMINE THE PECULIAR VELOCITIES OF CLUSTERS OF GALAXIES

We have investigated the possibility of inferring peculiar velocities for clusters of galaxies from the Doppler shift of scattered cosmic mi crowave background (CMB) photons. We find that if the core radius of t he gas distribution or the beamsize of the instrument is larger than 3 -7 arcmin, then the attainable signal-re-noise ratio is limited by con fusion with primary fluctuations. For smaller angular scales, 'cosmic confusion' is less important and instrumental noise and/or foreground emission will be the limiting factor. For a cluster with the optical d epth of the Coma cluster and for an optimal filtering technique, typic al one sigma errors span the wide range from 400 to 1600 km s(-1), dep ending on the cosmological model, the resolution of the instrument, an d the core radius of the cluster. The results have important implicati ons for the design of future high-resolution surveys of the CMB. Indiv idual peculiar velocities will be measurable only for a few fast movin g clusters at intermediate redshift unless cosmic fluctuations are sma ller than most standard cosmological scenarios predict. However, a rel iable measurement of bulk velocities of ensembles of X-ray bright clus ters will be possible on very large scales (100-500 h(-1) Mpc).