posted on 2023-05-23, 17:56authored byLockman, FJ, Pidopryhora, Y
The extra-planar HI in the inner parts of the Milky Way has been discovered to contain numerous cloud-like structures when observed in the 21 cm line with the Green Bank Telescope. These halo clouds have motions consistent with Galactic rotation and do not seem to be related to the classic high-velocity clouds. They are found to distances >1 kpc from the plane and can contain hundreds of M☉ of HI. Spectra of many of the halo clouds show evidence of coexisting cool and warm HI phases. A preliminary high-resolution study of one of the clouds suggests that it consists of a di®use envelope and a few dense cores, with a peak NH I reaching 4 X 1020 cm-2. The clouds are often organized into larger structures, one example of which was discovered near ζ = 35° rising higher than 2 kpc above the Galactic plane. New observations should answer some fundamental questions about the nature of these clouds.
History
Publication title
Proceedings of the Astronomical Society of the Pacific Conference 2004
Volume
331
Editors
R Braun
Pagination
59-66
Department/School
School of Natural Sciences
Publisher
Astronomical Society of the Pacific
Place of publication
San Francisco, USA
Event title
Astronomical Society of the Pacific Conference 2004