Effect of the environment on the fundamental plane of elliptical galaxies

We present an analysis of the location of interacting E/S0 galaxies on the Fundamental Plane (FP). Using the NEMO package, we performed N-body simulations of close encounters and mergers of two self- gravitating spherical galaxies. Two models for encounting galaxies { Plummer's and Hernquist's { were used. The number of particles ranged from 20 000 to 50 000 per galaxy. The changes of central density, half-mass radius and central velocity dispersion were analysed. It was found that close encounters between galaxies alter noticeably the above parameters within a very short time interval (10 7 {10 8 years) just before the nal merger. The ampli- tudes of parameter changes strongly depend on the initial mass concentration of a model. In some experiments we considered an encounter of two spherical galaxies with dark matter components. The eect of parameter changes was less pronounced than for the experiments without a dark halo. The results of the simulations were used to discuss the FP for interacting early-type galaxies.