This is a simulation of the evolution of a cool, dense gas cloud embedded in a hot, thin, surrounding medium. The cool gas starts off as a nice neat sphere with a randomised velocity field, so different parts of the cloud are moving at different speeds in different directions. The idea (not mine !) is that the pressure from the surrounding gas, given the specific numbers that we're dealing with, will be able to keep the cool gas in place, so the cloud shouldn't evolve too much. And that would explain why we detect gas clouds in the Virgo cluster that aren't forming any stars.
... which is of course not what happens. The disordered motions of the gas causes it to fragment, allowing the hot, high-pressure gas to penetrate the cloud and help blast it apart. Now if the motion was due to thermal pressure, which would act uniformly and push back neatly against the surrounding gas, it might work. But turbulent bulk motions have a completely different effect.
A proper animation showing how the cloud evolves should be ready quite soon.
That's probably how Pollock did it, too.
ReplyDeleteI get what you said, that the disordered motions of the gas causes it to fragment, but if it started off as a "nice neat sphere" why didn't collapse gravitationally?
ReplyDeleteHow did the gas cloud become a sphere?
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