How is the speed of the solar system through the dark matter halo determined?
Direct dark matter detection experiments rely on this speed estimate. Assuming the sun/earth travel through the dark matter halo, the relative speed difference between the sun/earth and the halo would result in a net dark matter 'wind'. As far as I understand, this wind would provide most of the kinetic energy needed for the dark matter to scatter to nuclei in the detector.
But how do we know the dark matter halo is not co-rotating with the luminous disk around the center of the galaxy? If it would, the wind may even be absent, and dark matter would be much harder detect in direct detection experiments.