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High Velocity Cloud Edges and Mini-HVCs by Hoffman, G. L.; Salpeter, E. E.; Pocceschi, M. G. is a scholarly article available to read on EtoBox.

What is High Velocity Cloud Edges and Mini-HVCs about?

Arecibo mapping is reported of the neutral hydrogen distribution along selected directions out from the centers of two small High Velocity Clouds (HVC), W486 and W491. Both HVCs have a small inner region where the neutral hydrogen column density N_HI decreases slowly and a larger outer region where N_HI declines more rapidly, smoothly and exponentially from ~ 2 X 10^19 atoms cm^-2 down to < 10^18 atoms cm^-2. Line widths, and presumably temperature and turbulence, do not increase in the outermost regions. Therefore pressure decreases smoothly, making confinement by dark matter gravity more likely than confinement by external pressure. The more extended HVC, W491, has a superimposed small cloud (which we dub a ``mini-HVC''), offset by 66 km s^-1 in velocity along the line of sight with peak column density about 5 X 10^18 atoms cm^-2. Preliminary data toward future mapping of two more HVCs reveals two more mini-HVCs of similarly small size and central column density a bit less than 1 X 10^19 atoms cm^-2. We suggest that these three mini-HVCs are not physically associated with the HVCs on which they are superimposed, but are either very small outlyers of the extended Magellanic Stream

Author

Hoffman, G. L.; Salpeter, E. E.; Pocceschi, M. G.

Published

2002

Language

EN