Implications of the Distribution of HI Clouds in the Lower Galactic Halo

¹ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H39, PO Box 218, Hawthorn, Victoria 3122, Australia ;
e-mail: alyson@astro.swin.edu.au
² Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia
³ National Radio Astronomy Observatory, PO Box 2, Green Bank, WV 24944, USA

Abstract

We have detected hundreds of HI clouds in the lower Galactic halo within the Galactic All-Sky Survey pilot region, a region spanning 325^∘≤ l ≤ 343^∘ and |b|≤ 20^∘. The motions of these clouds are governed by Galactic rotation, they are seen within the disk and up to heights of 2.5 kpc, and they span a wide range of Galactocentric radii. However, these clouds are not uniformly distributed and appear to be associated with Galactic structures such as spiral arms or superbubbles.