Simulation by the University of Washington N-body shop.
Left column shows the path of a single galaxy through the galaxy cluster. As it is subject to tidal shocks passing the other galaxies, the stars and dark matter are heated and some are lost to the tidal field of the entire cluster. The evaporated stars and dark matter form a long tail.
Right column zooms in on the gas in the galaxy, which steadily evolves via shocks and cooling and gravitational torques, into a compact nuclear disk. This disk likely gives rise to a high star formation rate.
The movie of this sequence is here (27 Mb).
Note: Dark Matter in blue; Stars in yellow; Gas in red.
