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Where Does the Disk Turn Into the Halo? Cool HI in the Outer Milky Way Disk
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.
History
Publication title
EAS Publications SeriesVolume
56Editors
M. A. de AvillezPagination
205-208ISBN
978-2-7598-0787-1Department/School
School of Natural SciencesPublisher
E D P SciencesPlace of publication
FranceEvent title
The Role of the Disk-Halo Interaction in Galaxy Evolution: Outflow vs. Infall?Event Venue
Espinho, PortugaDate of Event (Start Date)
2008-08-18Date of Event (End Date)
2008-08-22Repository Status
- Restricted