We have measured the velocities of 19 planetary nebulae (PNs) in the outer regions of the giant earlytype galaxy NGC 4406 in the Virgo cluster. The kinematics of the outermost regions, at a mean radius of 142A or 11 kpc, show rapid rotation and a low observed velocity dispersion (D166 and 96 km s~1, respectively), compared with the central velocity dispersion of about 210 km s~1. This supports the classiÐcation of this galaxy as an S0. Although this galaxy has a systemic velocity of [227 km s~1, we found three PNs with velocities close to the mean velocity of the Virgo cluster (about 1400 km s~1). We argue that these three PNs may be members of an intracluster stellar population in the Virgo cluster.

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Abstract.Photometry and kinematics of the giant elliptical galaxy NGC 5128 (Centaurus A) based on planetary nebulae observations (Hui et al. 1995) are used to build dynamical models which allow us to infer the presence of a dark matter halo. To this end, we apply a Quadratic Programming method. Constant mass-to-light ratio models fail to reproduce the major axis velocity dispersion measurements at large radii: the prole of this kind of models falls o too steeply when compared to the observations, clearly suggesting the necessity of including a dark component in the halo. By assuming a mass-to-light ratio which is increasing with radius, the model satisfactorily matches the observations. The total mass for the best t model is 4 10 11 M of which about 50% is dark matter. However, models with di erent total masses and dark halos are also consistent with the data; we estimate that the total mass of Cen A within 50 kpc may v ary between 3 10 11 M and 5 10 11 M . The best t model consists of 75% of stars rotating around the short axis z and 25% of stars rotating around the long axis x. Finally, the morphology of the projected velocity eld is analyzed using Statler's classi cation criteria (Statler 1991). We nd that the appearance of our velocity eld is compatible with a type 'Nn' or 'Nd'.

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