Sanjoy K. Sarker, Allen Stern
We first deduce the density profiles and gravitational potential functions in the haloes of four galaxies (NGC 2403, NGC 2841, NGC 3521 and NGC 5055) using the rotation velocity data from THINGS. The analysis only requires that spherical symmetry is valid far from the disk. We find that the density decreases exponentially with the potential in substantial regions of the halo far from the disk, in agreement with the description of a single-component isothermal Boltzmann gas. We then compare the rotational velocity data with that obtained from solutions of the Poisson equation for a self-gravitating isothermal Boltzmann gas in regions $r>R_{\tiny {\tt G}}$ of the halo, $r$ denoting the distance from the galactic origin. The minimum radius $R_{\tiny {\tt G}}$ can be varied, and good fits are obtained for a range of values for $R_{\tiny {\tt G}}$. Finally, for each galactic halo, we make three independent determinations of a constant for the Boltzmann gas, namely, the particle mass divided by the temperature, and find the results to be in general agreement.
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http://arxiv.org/abs/1302.2967
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