Dynamical Evolution of Galaxies in Clusters

Tidal forces acting on galaxies in clusters lead to a strong dynamicalevolution. In order to quantify the amount of evolution, I run self-consistentN-body simulations of disk galaxies for a variety of models in thehierarchically forming clusters. The tidal field along the galactic orbits isextracted from the simulations of cluster formation in the Omega_0=1;Omega_0=0.4; and Omega_0=0.4, Omega_Lambda=0.6 cosmological scenarios. Forlarge spiral galaxies with the rotation speed of 250 km/s, tidal interactionstruncate massive dark matter halos at 30 +- 6 kpc, and thicken stellar disks bya factor 2 to 3, increasing Toomre's parameter to Q > 2 and halting starformation. Low density galaxies, such as the dwarf spheroidals with thecircular velocity of 20 km/s and the extended low surface brightness galaxieswith the scale length of 10-15 kpc, are completely disrupted by tidal shocks.Their debris contribute to the diffuse intracluster light. The tidal effectsare significant not only in the core but throughout the cluster and can beparametrized by the critical tidal density. The tidally-induced evolutionresults in the transformation of the infalling spirals into S0 galaxies and inthe depletion of the LSB population. In the low Omega_0 cosmological models,clusters form earlier and produce stronger evolution of galaxies.Comment: accepted to Ap