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Where Does the Disk Turn Into the Halo? Cool HI in the Outer Milky Way Disk


Dickey, JM, Where Does the Disk Turn Into the Halo? Cool HI in the Outer Milky Way Disk, EAS Publications Series, 18-22 August 2008, Espinho, Portuga, pp. 205-208. ISBN 978-2-7598-0787-1 (2013) [Non Refereed Conference Paper]

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DOI: doi:10.1051/eas/1256032


Using HI absorption spectra taken from the recent surveys of λ 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 HI 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 HI, with the rest warm.

Item Details

Item Type:Non Refereed Conference Paper
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, JM (Professor John Dickey)
ID Code:85118
Year Published:2013
Deposited By:Mathematics and Physics
Deposited On:2013-06-14
Last Modified:2017-06-20

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