Session 2D Lectures by Fellows/Associates

Plasma laboratories on megaparsec-scales

Our Universe on large scales is like a "web" in which  the nodes are the most massive gravitationally systems (about 10^15 solar masses) called the galaxy clusters. Clusters of galaxies hold large reservoirs of baryons in the form of diffuse gas called the intra-cluster medium (ICM). The ICM is a blob of plasma on megaparsec (~3 million light years) scales whose properties are poorly known. It contains mainly thermal gas of temperature about ten million Kelvin, and is weakly magnetised with field strength of about a micro Gauss. The cosmic rays and magnetic fields, referred to as the non-thermal components, elude detection in most spectral bands and thus have remained the least understood components of the ICM. The relativistic electrons in the ICM manifest the non-thermal components at low radio frequencies (<= GHz) via synchrotron radiation providing a direct probe of their life cycle. I will describe our work towards characterising the cosmic rays and magnetic fields in the ICM with the Giant Metrewave Radio Telescope and the prospects with the next generation radio telescopes.