  We present the analysis of the velocity structure of the intracluster gas
near the core of Abell 3526 obtained with two off-center Chandra observations,
specifically designed to eliminate errors due to spatial variations of the
instrumental gain. We detected a significant velocity gradient along the
direction NE-SW direction, roughly perpendicular to the direction of the
incoming sub-group Cen45, in agreement with previous ASCA SIS measurements. The
presence of gas bulk velocities is observed both with and without the inclusion
of the FeK line complex in the spectral fittings. The configuration and
magnitude of the velocity gradient is consistent with near transonic
circulatory motion, either bulk or eddy-like. The velocity difference obtained
using the best calibrated central regions of ACIS-S3 is found to be
(2.4+-1.0)E03 km/s for rectangular regions 2'.4 x 3' roughly diametrically
opposed around the cluster's core. There are also indications of a high
velocity zone towards the Southern region with similar magnitudes. The
detection of velocity gradients is significant at the >99.4% confidence and
simulations show that intrachip gain fluctuations > 1800 km/s are required to
explain the velocity gradient by chance. The measurements suggest that >1% of
the total merger energy can still be bulk kinetic 0.4 Gyr after the merging
event. This is the first direct confirmation of velocity gradients in the
intracluster gas with independent instruments and indicates that strong
departure from hydrostatic equilibrium is possible even for cool clusters that
do not show obvious signs of merging.
