Origin of high-velocity hydrogen gas -- AMIGA Astronomy

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Subject: Origin of high-velocity hydrogen gas

Author:
Susan

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Date Posted: 23:22:45 05/14/03 Wed

Forty years ago astronomers discovered clouds of hydrogen gas. These clouds have now been found to be gravitationally bound to our galaxy. These clouds are probably material stripped from small galaxies and that they are now companions of the Milky Way.
It's possible that the clouds were created by some sort of a fountain of material from our Milky Way or via interaction with the Magellanic Clouds.
This has important implications for the dark-matter distribution in groups of galaxies like our own Local Group. Some galaxy formation models predict that there are small lumps or "halos" of cold darkmatter scattered throughout the Local Group. This high-velocity cloud may represent these otherwise-invisible halos of dark matter.
If the high-velocity clouds traced the locations of these dark matter halos, you'd expect the clouds to be strewn throughout the Local Group. But because the gas clouds are only found close to the Milky Way they cannot be associated with the dark matter halos. While dark matter halos may still roam the Local Group, they aren't associated with these streaming clouds of hydrogen.

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