Multiple shock structures in a radio selected cluster of galaxies
  We present a new radio-selected cluster of galaxies, 0217+70, using
observations from the Very Large Array and archival optical and X-ray data. The
new cluster is one of only seven known that has candidate double peripheral
radio relics, and the second of those with a giant radio halo (GRH), as well.
It also contains unusual diffuse radio filaments interior to the peripheral
relics, and a clumpy, elongated X-ray structure. All of these indicate a very
actively evolving system, with ongoing accretion and merger activity,
illuminating a network of shocks, such as those first seen in numerical
simulations. The peripheral relics are most easily understood as outgoing
spherical merger shocks with large variations in brightness along them, likely
reflecting the inhomogeneities in the shocks' magnetic fields . The interior
filaments could be projections of substructures from the sheet-like peripheral
shocks, or they might be separate structures due to multiple accretion events.
ROSAT images show large-scale diffuse X-ray emission coincident with the GRH,
and additional patchy diffuse emission that suggests a recent merger event.
This uniquely rich set of radio shocks and halo offer the possibility, with
deeper X-ray, optical and data higher resolution radio observations, of testing
the models of how shocks and turbulence couple to the relativistic plasma.
0217+70 is also over-luminous in the radio compared to the empirical
radio-X-ray correlation for clusters -- the third example of such a system.
This new population of diffuse radio emission opens up the possibility of
probing low-mass cluster mergers with upcoming deep radio continuum surveys.
