Effect of pressure in a nebula?

[NeuroFuzzy]

So... I'm trying my hand at programming an n-body simulation. For those of you unfamiliar, that is a simulation where every body attracts every other body. I have something effectively like this:
http://www.youtube.com/watch?v=byI9yhITDsM"

But now... these straightforward n-body simulations seem to do a poor job of simulating galaxies. There's no "gas" behavior, and so most of the time whatever I simulate tends to form a globular cluster, and it tends to stay that way.

Now, from what I've gathered, milky-way style systems (that tend to have most of their mass on a plane) tend to form because of gas<->gas interactions during the formation of the system. So I'm thinking about adding in a hydrodynamics simulation to more accurately describe the system. My question is: What is the pressure inside a nebula, and over what time scales would the force of this pressure be significant?

I'm planning on using an SPH/compressible flow simulation.

 

[zhermes]

Kudos to you sir. If you're not familiar with it, you might want to take a look at GADGET---just as a reference / inspiration.

The pressure varies greatly based on the type of nebula, and the location inside of it. Generally the dynamical timescale is the one of interest.

A situation you might want to consider is a (small) globular cluster, and think about its interactions with the galactic disk. You could treat the gas component in terms of its effects alone (e.g. dynamical friction) instead of actually modelling it---which makes it much more complicated.

I'm not familiar with any attempts in particular, but it seems like it would be difficult to treat the gas with SPH while preserving each star as an independent, single, body.