The structure of cluster merger shocks: turbulent width and the electron heating time-scale

ABSTRACT We present a new $2\rm \, Ms$Chandra observation of the cluster merger Abell 2146, which hosts two huge M ∼ 2 shock fronts each ${\sim }500\rm kpc$ across. For first time, we resolve and measure width shocks. The best-fitting for bow is $17\pm 1\rm upstream $10.7\pm 0.3\rm kpc$. A narrow collisionless will appear broader in projection if its smooth shape warped by local gas motions. show that both widths are consistent with shocks blurred motions $290\pm 30{\rm km\rm s^{-1}}$. forms later on than therefore expected to be significantly narrower. From electron temperature profile behind shock, time-scale electrons ions come back into thermal equilibrium. rule out rapid equilibration shock-heated at 6σ level. observed instead favours collisional equilibration. these shocks, have low sonic Mach numbers propagate through high β plasma, find no evidence heating over produced adiabatic compression. Our findings valid similar parameters other environments support existing picture from solar wind supernova remnants. this result but has more complex structure, including ${\sim}2\rm keV$ increase }50\rm ahead shock.