We present a 250 ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front .
The new data reveal that the edge is coherent over a larger opening angle and is significantly more bow-shock-shaped than previously thought .
Within \sim 27 \arcdeg about the axis of symmetry of the edge the density , temperature and pressure drop abruptly by factors of 1.83 ^ { +0.09 } _ { -0.08 } , 1.85 ^ { +0.41 } _ { -0.41 } and 3.4 ^ { +0.8 } _ { -0.7 } , respectively .
This is inconsistent with the pressure equilibrium expected of a cold front and we conclude that the edge is a shock front .
We measure a Mach number M = 1.59 ^ { +0.06 } _ { -0.07 } and corresponding shock velocity v _ { shock } \simeq 2057 { km s ^ { -1 } } .
Using spectra collected at the MMT with the Hectospec multi-object spectrograph we identify 328 spectroscopically confirmed cluster members .
Significantly , we find a local peak in the projected galaxy density associated with a bright cluster galaxy which is located just ahead of the nose of the shock .
The data are consistent with a merger viewed within \sim 23 \arcdeg of the plane of the sky .
The merging subclusters are now moving apart along a north-south axis approximately 0.3 Gyr after a small impact parameter core passage .
The gas core of the secondary subcluster , which was driving the shock , appears to have been disrupted by the merger .
Without a driving “ piston ” we speculate that the shock is dying .
Finally , we propose that the diffuse radio emission near the shock is due to the revival of pre-existing radio plasma which has been overrun by the shock .