I How to Convert Plummer Distribution of Stars Parameters into Standard Units?

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The discussion focuses on converting parameters from a Plummer distribution of stars into standard units, specifically for a simulation involving N stars of mass m within a defined volume. The user seeks clarification on how to convert the calculated positions (x, y, z) and velocities (u, v, w) into meters and meters per second. They reference a specific PDF document that outlines the Plummer density function and provide equations for generating star positions and velocities using random numbers. The user acknowledges understanding the calculations but struggles with the final conversion to standard units. The conversation highlights the need for clearer guidance on the conversion process for the star parameters.
jimbo007
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Hi all,
I refer to the following pdf document, in particular the appendix:
http://adsabs.harvard.edu/cgi-bin/n.....37..183A&link_type=ARTICLE&db_key=AST&high=

End goal is to distribute N stars each having mass m (looks like equal mass stars is the easiest scenario) within a box who has each side of length 3 \times 10^{17} \text{m} so that the total mass is M. I think I understand that you can't get all stars in the box but as long as most are in the box that should be close enough.

There are some parts of this document I don't understand but will take on faith that it is true.

I do understand how the position (x,y,z) and velocity (u,v,w) are calculated but not sure how to convert them to metres and metres/sec.

Does anyone know how to convert each stars mass m, position (x,y,z) and velocity (u,v,w) into kg, m and m/s?

Thanks!
 
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I probably should at least put a few more equations into make things a bit easier. Plummer's density is given by:
\rho(r) = \frac{3M}{4\pi R^3}\left( 1+ \left(\frac{r}{R} \right)^2 \right)^{-\frac{5}{2}}
where
M = total mass of star cluster
R = magic scaling parameter

Now let X_{n} be a uniformly distributed random number between 0 and 1. (x, y, z) is the position of the star and (u, v, w) is the velocity of the star

<br /> \mathbf{x} = \begin{pmatrix}x \\ y \\ z\end{pmatrix} \\<br /> \dot{\mathbf{x}} = \begin{pmatrix} u \\ v \\ w \end{pmatrix}<br />
then
<br /> r = \left(X_{1}^{-\frac{2}{3}} - 1 \right)^{-\frac{1}{2}} \\<br /> z = \left( 1-2X_{2} \right) r<br />
x, y, u, v and w and calculated in a similar fashion. The last paragraph in the pdf says to multiply these variables by a few numbers but it's not clear to me how to convert z to metres
 
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