When Galaxy Clusters Collide: Shocking tales of structure formation

Wed 2 May, 2018 @12:00 PM, level 7
Dr Andra Stroe, European Southern Observatory,
Garching

Email:  astroe[at]eso.org

Abstract

Red weather alert: dangerous cosmic weather forecast, in light of galaxy cluster mergers! Clusters grow through mergers with other clusters, events which give rise to the largest cosmic shock waves. Shocks travel like giant tsunamis through the electron plasma and shape the evolution of the intra-cluster medium. Giant radio relics trace these shock fronts and are thought to form when accelerated electrons emit synchrotron radiation in the presence of a magnetic field. I will present results from the widest frequency study of radio relics, where we combine, for the first time, data covering more than 2 order of magnitude in radio frequency. Our very low and very high radio frequency data challenge the simple, widely accepted model for relic formation. Using unique observations spanning the 150 MHz to 30 GHz range, I will derive physical parameters, such as Mach numbers and electron ages, as well as constrain injection mechanisms. I will also discuss how new models involving re-acceleration of aged seed electrons or evolving magnetic fields can alleviate the discrepancies between observations of relics and theory.