`Rings' of diffuse radio emission surrounding the Bullet cluster
  We present the discovery of ringlike diffuse radio emission structures in the
peripheral regions of the Bullet cluster 1E 0657$-$55.8. Ring formations are
spanning between 1--3 Mpc away from the center of the cluster, significantly
further away from the two already reported relics. Integrated fluxes of four of
the sub-regions in the inner `ring' from 4.5 to 10 GHz have also been reported.
To understand the possible origin of these structures, here we present a maiden
attempt of numerical modelling of a 3D and realistic `bullet' like event in a
full cosmological ($\Lambda$CDM) environment with N-body plus hydrodynamics
code. We report a simulated `bullet' found inside a (128 Mpc)$^3$ volume
simulation with a speed of 2700 km s$^{-1}$, creating a high supersonic bow
shock of Mach $M=3.5$ and a clear evidence of temporal separation of dark
matter and baryons, assuring no challenge to $\Lambda$CDM cosmology from the
bullet event as of now. We are also able to unveil the physics behind the
formation of these observed multiple shock structures. Modelled radio emissions
in our simulation support a complex combination of merger-associated processes
that accelerates and re-accelerates fossil and cosmic-ray electrons. With a
time evolution study and the computed radio emissions, we have shown that the
ring like formation around the bullet is originated due to the interaction of
the strong merger shocks with the accretion shocks at the periphery. The
multiple shock structures observed are possibly originated from multiple
mergers that have taken place at different times and much before the bullet
event.
