The Disc That Just Won't Die

OK, so I am now in the stage of doing science runs. Here's my stable gas disc suddenly finding itself in the very centre of a galaxy cluster. Unfortunately, the 400 massive galaxies surrounding it are difficult to visualise because they move so quickly. You'll just have to use your imagination. I also decided not to show the dark matter because it gets in the way and doesn't do anything.

But after some initial fireworks, the disc doesn't do a lot either. Initially the disc happens to be near the centre of one of the massive galaxies and it's moving away from it, so it experiences massive tidal forces. After that though, it never has such a close encounter and things settle down. About half of the mass that was originally in the disc stays in the disc. The thing is practically indestructible. Mind you, using this much dark matter is right on the limit of what the observations say it could contain. It could be smaller and need far less.

Next week I'll run more of these starting at different points within the cluster to see how statistically likely it is that such a dark galaxy could survive. Based on previous experiments I don't expect there to be much difference, but it's possible that sometimes the galaxy will experience much more violent encounters.

Of course, this is quite crude and missing a lot of physics like star formation and the gas inside the cluster itself. But if the quest to get a stable disc shows anything, it's that it pays to use a slow, steady, incremental approach.