  Several recent numerical simulations of off-center cluster mergers predict
that significant angular momentum with associated velocities of a few x 10^{3}
km/s 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, 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 ~3.4+-1.1 x 10^{3}
km/s. 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.
