Multi-stage Three Dimensional Sweeping and Annealing of Disc Galaxies in Clusters

We present new three dimensional, hydrodynamic simulations of the ram pressure stripping of disc galaxies via interaction with an hot intracluster medium (ICM). The simulations were carried with the smoothed-particle hydrodynamics, adaptive mesh 'Hydra' code (SPH-A$P^3$M), with model galaxies consisting of dark halo, and gas and stellar disc components. The simulations also include radiative cooling, which is important for keeping the warm, diffuse gas of moderate density from being unrealistically heated by the ICM. We examine the role that wind velocity, density and galaxy tilt play in gas stripping. The onset of the ICM wind has a profound effect on the disc gas that is not immediately stripped. This remnant disc is displaced relative to the halo center and compressed. This can trigger gravitational instability and the formation of numerous flocculent spirals. These waves transport angular momentum outward, resulting in further compression of the inner disc and the formation of a prominent gas ring. This 'annealing' process makes the inner disc, which contains much of the total gas mass, resistant to further stripping, but presumably susceptible to global starbursts. When the mass loss and annealing processes go to completion we find that the total amount of mass lost from a fixed target galaxy is well fit by a simple power-law function of a dimensionless parameter that combines the ram pressure and internal properties of the galaxy. (abs. abbreviated)