HIGH ANGULAR RESOLUTION OBSERVATION OF THE SUNYAEV–ZEL'DOVICH EFFECT IN THE MASSIVE z ≈ 0.83 CLUSTER Cl J0152–1357

Abstract

X-ray observations of galaxy clusters at high redshift (z>0.5) indicate that they are more morphologically complex and less virialized than those at low-redshift. We present the first subarcmin resolution at 18 GHz observations of the Sunyaev-Zel'dovich (SZ) effect for ClJ0152-1357 using the Australia Telescope Compact Array. ClJ0152-1357 is a massive cluster at redshift z=0.83 and has a complex structure including several merging subclumps which have been studied at optical, X-ray, and radio wavelengths. Our high-resolution observations indicate a clear displacement of the maximum SZ effect from the peak of X-ray emission for the most massive sub-clump. This result shows that the cluster gas within the cluster substructures is not virialised in ClJ0152-1357 and we suggest that it is still recovering from a recent merger event. A similar offset of the SZ effect has been recently seen in the `bullet cluster' by Malu et al. This non-equilibrium situation implies that high resolution observations are necessary to investigate galaxy cluster evolution, and to extract cosmological constraints from a comparison of the SZ effect and X-ray signals.