Catching the `Bullet' with Parkes: A Pilot Study for large-scale galaxy cluster observations

We propose to observe the ‘bullet’ cluster of galaxies - 1E 0657-56 - which consists of two sub-clusters in the process of merging and manifests relatively cold clouds plowing through hot intra-cluster gas, using the Parkes Telescope at 18 GHz. We aim to image the sub-structure in the gas pressure distribution via the inverse-Compton scattering of cosmic microwave background photons (the Sunyaev-Zeldovich Effect; SZE). The observations constitute a probe of fine structure in the physical state of the intra-cluster gas, the physics of propagation and stability of cold fronts in cluster mergers and a measure of cluster magnetic field. The small scale structure has been observed with the ATCA already (Wilson et al. MNRAS 2011; Malu et al. arXiv:1005.1394), but the large scale emission, essential to recover the entire amount of the SZ effects, is missed by those observations because of lack of sensitivity on scales larger than the primary beam. Combining with single dish observations is thus essential to derive cluster physical quantities (like electron density and gas temperature) and we propose here to conduct them with the Parkes telescope.