Probing the Halo of Centaurus A: A Merger Dynamical Model for the PN Population

Extract

We use planetary nebulae observations (Hui et al. 1995) to build dynamical models of the dust-lane elliptical galaxy NGC 5128 (Centaurus A). The PN photometric and kinematical data extend out to 20 kpc (∼ 4r _e) along the major axis and 10 kpc along the minor axis. Our models are built using a Quadratic Programming technique (Dejonghe 1989). The method produces fits to the data set, which consists of the photometry field (E2, well fitted by a r ^1/4-law) together with the major- and minor- axis rotation curves and velocity dispersion profiles. Assuming the merger hypothesis for Cen A, we describe its kinematics in a spherical potential by two sub-systems, one rotating about the intrinsic short axis and the other about the intrinsic long axis of the galaxy.