The cluster of galaxies A754 undergoes a merger of several large structural units .
X-ray observations show a nonequilibrium state of the central part of the cluster , in which a cloud of cold plasma 500 kpc in size was identified amid the hotter cluster gas .
The X-ray image of A754 exhibits a brightness discontinuity , which can be interpreted as a shock wave in front of a moving cloud of dense gas.The shock parameters are determined from the jump in intergalactic gas density using the ROSAT image .
The estimated Mach number is M _ { 1 } = 1.71 ^ { +0.45 } _ { -0.24 } at a 68 % confidence level .