2009/01/16 by John M. Dickey, J. M. Dickey, Dickey, John M.
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.48550/arxiv.0901.2379
5 pages, 3 figures, Conference Proceedings "The Role of Disk-Halo Interaction in Galaxy Evolution, Outflow vs. Infall?" ed. M. A. de Avillez, European Astronomical Society Publications, 2009 in press
arxiv created 2009/01/16 · openalex publication_date 2009/01/16 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Using H I absorption spectra taken from the recent surveys of 21-cm line and continuum emission in the Galactic plane, the distribution of cool atomic clouds in the outer disk of the Milky Way is revealed. The warp of the midplane is clearly seen in absorption, as it is in emission, and the cool, neutral medium also shows flaring or increase in scale height with radius similar to that of the warm atomic hydrogen. The mixture of phases, as measured by the fraction of H I in the cool clouds relative to the total atomic hydrogen, stays nearly constant from the solar circle out to about 25 kpc radius. Assuming cool phase temperature ~50 K this indicates a mixing ratio of 15% to 20% cool H I, with the rest warm.