The Kinematics of the Planetary Nebulae in the Outer Regions of NGC 4406

Abstract

We have measured the velocities of 19 planetary nebulae (PNs) in the outer regions of the giant early-type galaxy NGC 4406 in the Virgo cluster. The kinematics of the outermost regions, at a mean radius of 142″ or 11 kpc, show rapid rotation and a low observed velocity dispersion (∼166 and 96 km s -1 , respectively), compared with the central velocity dispersion of about 210 km s -1 . This supports the classification 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. © 1996. The American Astronomical Society. All rights reserved.