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K.C. Freeman (Australian National University)
It is possible, with 4-m telescopes, to detect individual planetary nebulae and measure their velocities out to distances of about 20 Mpc. This makes planetary nebulae excellent dynamical tracers of very diffuse stellar populations like the far outer regions of galaxies and the very faint intracluster stellar medium of nearby clusters of galaxies. Results so far include spectroscopic confirmation of the existence of a intracluster stellar population in the Virgo cluster, and the discovery that some giant elliptical galaxies show rapid rotation in their outer regions, as predicted from simulations of mergers and hierarchical galaxy formation.