Dark Matter Question

[LaurieAG]

I realize there is a reason out there, but can someone link me a good, detailed reason, or even better, explain it here?

Some of the latest research on local dark matter is interesting.
http://www.ras.org.uk/news-and-press...or-dark-matter

But the rebuttal paper is even more interesting. http://arxiv.org/abs/1205.4033

An analysis of the kinematics of 412 stars at 1-4 kpc from the Galactic mid-plane by Moni Bidin et al. (2012) has claimed to derive a local density of dark matter that is an order of magnitude below standard expectations. We show that this result is incorrect and that it arises from the assumption that the mean azimuthal velocity of the stellar tracers is independent of Galactocentric radius at all heights.

It seems that the main difference between the two results is that when you use a common galactic center of rotation you don't get DM but when you use a galactic axis of rotation you do.