It has been recently suggested that a significant fraction of the neutral hydrogen clouds in our Galaxy have a cloud-cloud velocity dispersion of 35 km s⁻¹ (Radhakrishnan and Srinivasan). Using H I emission data, the authors find that, indeed, a detectable amount of higher than normal velocity-dispersion H I exists. However, the fraction of H I in these clouds is about an order of magnitude less than that suggested by Radhakrishnan and Srinivasan. This "fast" H I constitutes less than 5% of the volume density of the H I in the galactic plane. It probably constitutes ≤20% of the total mass of galactic H I but contains most of the kinetic energy of the ISM.
No takes yet. Share an insight, caveat, or question.
Kulkarni et al. (1985) studied this question.