Kinematics of the southern galaxy cluster Abell 3733

We report radial velocities for 99 galaxies with projected positions within 30 0 of the center of the clus- ter A3733 obtained with the MEFOS multiber spectro- graph at the 3.6-m ESO telescope. These measurements are combined with 39 redshifts previously published by Stein (1996) to build a collection of 112 galaxy redshifts in the eld of A3733, which is used to examine the kinemat- ics and structure of this cluster. We assign cluster mem- bership to 74 galaxies with heliocentric velocities in the interval 10 500 13 000 km s 1 . From this sample of clus- ter members, we infer a heliocentric systemic velocity for A3733 of 11 653 +74 76 km s 1 , which implies a mean cos- mological redshift of 0.0380, and a velocity dispersion of 614 +42 30 km s 1 . The application of statistical substructure tests to a magnitude-limited subset of the latter sample reveals evidence of non-Gaussianity in the distribution of ordered velocities in the form of lighter tails and possi- ble multimodality. Spatial substructure tests do not nd, however, any signicant clumpiness in the plane of the sky, although the existence of subclustering along the line-of- sight cannot be excluded.