Why are central radio relics so rare?
Article first published online: 16 MAR 2012
© 2012 The Author Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 421, Issue 3, pages 1868–1873, April 2012
How to Cite
Vazza, F., Brüggen, M., van Weeren, R., Bonafede, A., Dolag, K. and Brunetti, G. (2012), Why are central radio relics so rare?. Monthly Notices of the Royal Astronomical Society, 421: 1868–1873. doi: 10.1111/j.1365-2966.2011.20160.x
- Issue published online: 4 APR 2012
- Article first published online: 16 MAR 2012
- Accepted 2011 November 7. Received 2011 November 3; in original form 2011 September 22
- acceleration of particles;
- galaxies: clusters: intracluster medium;
- large-scale structure of Universe
In this paper, we address the question of why cluster radio relics that are connected to shock acceleration, so-called radio gischt relics, have preferentially been found in the outskirts of galaxy clusters. By identifying merger shock waves in cosmological grid simulations, we explore several prescriptions for relating the energy dissipated in shocks to the energy emitted in the radio band. None of the investigated models produces detectable radio relics within 100–200 kpc from the cluster centre. All models cause >50 per cent of the detectable relic emission at projected distances >800 kpc. Central radio relics caused by shocks that propagate along the line of sight are rare events for simple geometrical reasons, and they have a low surface brightness making them elusive for current instruments. Our simulations show that the radial distribution of observed relics can be explained by the radial trend of dissipated kinetic energy in shocks, which increases with distance from the cluster centre up until half of the virial radius.