A Global View of Molecule-Forming Clouds in the Galaxy

We have mapped cold atomic gas in 21cm line H i self-absorption (HISA) at arcminute resolution over more than 90% of the Milky Way's disk. To probe the formation of H2 clouds, we have compared our HISA distribution with CO J = 1-0 line emission. Few HISA features in the outer Galaxy have CO at...

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Bibliographic Details
Published in:Proceedings of the International Astronomical Union 2015-08, Vol.11 (S315), p.1-2, Article E27
Main Authors: Gibson, Steven J., Howard, Ward S., Jolly, Christian S., Newton, Jonathan H., Bell, Aaron C., Spraggs, Mary E., Hughes, J. Marcus, Tagliaboschi, Aaron M., Brunt, Christopher M., Taylor, A. Russell, Stil, Jeroen M., Dame, Thomas M.
Format: Article
Language:English
Subjects:
Astronomical bodies
Astrophysics
Clouds
Disks
Emission
Formations
Galaxies
Gases
Kinematics
Milky Way Galaxy
Molecules
Poster Papers
Star & galaxy formation
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Summary:We have mapped cold atomic gas in 21cm line H i self-absorption (HISA) at arcminute resolution over more than 90% of the Milky Way's disk. To probe the formation of H2 clouds, we have compared our HISA distribution with CO J = 1-0 line emission. Few HISA features in the outer Galaxy have CO at the same position and velocity, while most inner-Galaxy HISA has overlapping CO. But many apparent inner-Galaxy HISA-CO associations can be explained as chance superpositions, so most inner-Galaxy HISA may also be CO-free. Since standard equilibrium cloud models cannot explain the very cold H i in many HISA features without molecules being present, these clouds may instead have significant CO-dark H2.
ISSN:1743-9213
1743-9221
DOI:10.1017/S1743921316007882