The SZ effect and non-trivial clusters

The cluster temperature has been measured using the Sunyaev-Zeldovich (SZ) effect alone, finding excellent agreement with X-ray temperature determinations. However, the galaxy clusters are not iso-thermal, and the radial temperature dependence will affect the cluster parameters derived through the observation of the SZ effect. One finds that the Compton weighted electron temperature is accurately derived through SZ observations, however, the derived peculiar velocity will be systematically shifted by 10-20%. We also address the possibility that clusters are locally only in kinetic equilibrium (not in full local thermal equilibrium), which will affect the SZ effect. (c) 2006 Elsevier B.V. All rights reserved.