Space jellyfish !

This is a simulation in progress of a galactic disc being smashed with a wind from an external intracluster medium. Ram pressure stripping is a well-known phenomenon which is thought to be the main way gas gets stripped in galaxies in clusters. As galaxies fall through the hot, relatively thin gas of a galaxy cluster at high speed, the pressure of the external gas builds up to the point where it can push out the galaxy's own gas.

In this particular simulation, the gas in the galaxy's disc is especially thin (so as to prevent it forming stars, and match observations of some weird dark hydrogen clouds). This is a simple "wind tunnel" test, where we approximate the ram pressure by having the external gas move at a constant speed. Computationally this is much easier than setting up a galaxy falling through a cluster in a more realistic way. It's not too awful an approximation, but probably in this case the external gas is too thin and moving too quickly.

This simulation was done to burn up some CPU time we had left on a supercomputer. We didn't get as much as we'd like but we got enough to see something cool. The output files are still being converted into a format I can handle; expect a proper animation (this one is rotation only) in a few days.

Rendered in FRELLED : http://www.rhysy.net/frelled-1.html