Several recent numerical simulations of off-center cluster mergers predict that significant angular momentum with associated velocities of a few \times 10 ^ { 3 } km s ^ { -1 } can be imparted to the resulting cluster .
Such gas bulk velocities can be detected by the Doppler shift of X-ray spectral lines with ASCA spectrometers .
Using two ASCA observations of the Centaurus cluster ( Abell 3526 ) , we produced a velocity map for the gas in the cluster ’ s central regions .
We also detected radial and azimuthal gradients in temperature and metal abundance distributions , which seem to be associated with the infalling sub-group centered at NGC 4709 ( Cen 45 ) .
More importantly , we found a significant ( > 99.8 % confidence level ) velocity gradient along a line near-perpendicular to the direction of the incoming sub-group and with a maximum velocity difference of \sim 3.4 \pm 1.1 \times 10 ^ { 3 } km s ^ { -1 } .
It is unlikely ( P < 0.002 ) that the observed velocity gradient is generated by gain fluctuations across the detectors .
While the observed azimuthal temperature and abundance variations can be attributed to the interaction with Cen 45 , we argue that the intracluster gas velocity gradient is more likely due to a previous off-center merging event in the main body of the Centaurus cluster .