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I was wondering where I can get a more or less complete set of a galaxy to test an n-body simulation (preferably two colliding galaxies with approx 300k to 1M elements).

Is it possible to extract this data from a public source like Nasa? Or does it make more sense to just generate the data?

Note: I Found the SDSS Skyserver website, but I don't think it's possible process this data to get useful initial conditions and a more or less complete galaxy.

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I can't help you on this, but I know enough to ask for a clarification: Are you asking for actual star positions for stars in two galaxies? If so, you're not going to get it because it doesn't exist for real galaxies. –  Stuart Robbins Nov 1 '11 at 23:29
    
Well I'm quite happy with an approximation or a model as well. But now I'm really curios. What do you mean with "actual star positions"? How do people model simulations like the milky way? How do they justify their results? –  Pascal Nov 1 '11 at 23:49
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The Milky Way has about 7E11 Msun, so in a simulation that breaks that up into 300K-1M elements, each element is going to represent at least 700,000 Msun's worth of material on average. One common scheme for this is called Smooth Particle Hydrodynamics, in which each 700,000 Msun chunk is treated as an object that interacts with other, similar objects, exerting pressure and gravity, exchanging matter and energy, etc. (So yes, you're definitely looking for a model.) The justification is basically "astrophysics." There's a reason everyone who works in it has a PhD. Plus comparison to obs. –  Andrew Nov 2 '11 at 0:59
    
But where would you get this data if you wanted to simulate something like the Milky Way? Would you just use a model like the Plummer model and adjust the parameters in such a way that it loosely fits the galaxy? –  Pascal Nov 2 '11 at 9:01
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Try the folks over at Milky Way@Home. They are in the process of creating exactly what it sounds like you want, but they may ice you out until the project is completed and published, since this is their livelihood you're asking for. It's kind of like asking for the recipe to the Big Mac secret sauce or KFC's spices. Or maybe they will let you collaborate, if you have something constructive to contribute.

There's also this guy, who is apparently running simulations of a several tens of millions of elements on a supercomputer. Maybe he'd give you a random slice of 1% of his data points, and you could multiply the mass of each by 100, to give a lower-res dataset.

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Thank you, I will ask them. –  Pascal Nov 14 '11 at 0:20
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