Diffuse radio emission from bullet galaxy cluster

Abstract

Cluster of galaxies are the largest gravitationally bound systems in the universe, with mass of about 1015 times mass of the Sun and volume of about 100Mpc3(1pc =3.26 light years). In hierarchical process of structure formation the smaller units are galaxies which forms cluster. Small cluster of galaxies formed first and merged under large gravitational pull o f each other. In fact it appears some clusters are still growing through mergers. Major cluster mergers are among the most energetic events in the universe since the Big Bang. These clusters visible matter consist of galaxies and Intra Cluster Medium (ICM) which is usually plasma or hot gas. While merging process a huge release of gravitational energy heats up this plasma. This dissipated energy can be up to 1063 to 1064 ergs during one cluster crossing time [2]. Such Hot ICM emits thermal radiation in soft X-ray region via bremsstrahlung process. The ICM of many merging clusters studied extensively with optical and x-ray telescopes. In particular, a fraction of the energy that is dissipated during the hierarchica l sequence of matter accretion can be channeled into non-thermal plasma components, i.e. relativistic particles (cosmic rays or (CRs)) and magnetic fields in the ICM. In many merging clusters ICM is found to radiate in low frequency region i.e. radio regio n. ICM along with x-ray emission also emits radio waves through the non-thermal process. The non-thermal process involved is called as synchrotron radiation. So these observations proved that the ICM is mixed with highly relativistic particles and large scale magnetic fields. We here studying this diffuse non-thermal radiation detected in galaxy cluster merging event.