Extreme scattering events and Galactic dark matter
Abstract
Extreme Scattering Events (ESEs) are attributed to radio-wave refraction by a cloud of free-electrons crossing the line-of-sight. We present a new model in which these electrons form the photo-ionized 'skin' of an underlying cool, self-gravitating cloud in the Galactic halo. In this way we avoid the severe over-pressure problem which afflicts other models. The UV flux in the Galactic halo naturally generates electron densities of the right order. We demonstrate, for the first time, a good reproduction of the prototypical ESE in the quasar 0954+658. The neutral clouds are a few AU in radius and have masses less than about 10^{-3} solar. The observed rate of ESEs implies that a large fraction of the mass of the Galaxy is in this form.
Cite
@article{arxiv.astro-ph/9802111,
title = {Extreme scattering events and Galactic dark matter},
author = {Mark Walker and Mark Wardle},
journal= {arXiv preprint arXiv:astro-ph/9802111},
year = {2009}
}
Comments
5 pp incl 3 figs, LaTeX, uses aas2pp4.sty. Minor revisions. ApJ Letters in press