AAS 197, January 2001
Session 4. The Milky Way Galaxy
Display, Monday, January 8, 2001, 9:30am-7:00pm, Exhibit Hall

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[4.15] A New Survey for Faint Galactic High-velocity HI Clouds

F.J. Lockman (NRAO), E.M. Murphy (UVa), S.M. Petty-Powell (Evergreen St.), V.J. Urick (Bloomsburg Univ.)

We have completed a deep search for 21cm HI emission from high-velocity Galactic HI clouds in more than 800 directions at high Galactic latitudes. The observations, made with the NRAO 140 Foot Telescope, cover an LSR velocity range of -1000 to +800 km/s, and are more sensitive than previous surveys by a factor between three and eight, for large and small HI clouds, respectively. For a cloud which fills the 21 arc-min telescope beam, the detection limit corresponds to 7 x 1017 cm-2. We have found high-velocity HI above this level of NH in more than one-third of all directions surveyed. We will discuss the distribution and properties of the detected clouds, and the implications that these data have for models of the origin of the high velocity cloud population.

The NRAO is operated by AUI, under a cooperative agreement with the NSF. The research of S.Petty-Powell and V. Urick was supported by the NSF REU program.

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