Python 2D Jean Instability in Spiral Galaxy Simulation
First a warning, then a hack:

1) If you didn't run this simulation, if you are not a trained theoretical astronomer of undergraduate level or above, and if this simulation doesn't have the kind of data you need to answer the question you are asking you should not trust the results at all.

It takes years of study to understand the weird numerical effects (things that happen in the simulation because of the way it is set up that would never happen in reality), background physics and loads of assumptions and approximations that go into this kind of stuff. 

We often say 'garbage in, garbage out'. The answers you get from this will probably not be very illuminating because they say more about the simulation than real space.

2) That said, if you are just doing this for fun or to learn the skills, GREAT! Keep playing! And a very basic assumption you can make in order to get some numbers out (that will be quite wrong) is that all gas in space is ~10K.