AAS 200th meeting, Albuquerque, NM, June 2002
Session 42. Gaseous Galaxy Halos and Galaxy Edges
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

## [42.05] Rotation of Extraplanar Gas: Comparing Ballistic and Hydrostatic Models

R. Benjamin (University of Wisconsin-Madison)

The recent detection of gas well above the plane of galaxies in H\alpha emission and 21 cm HI emission allows us to determine for the first time how this gas rotates with respect to the underlying disk. The rotation of this gas has implications for models of radial mass transport, angular momentum transfer, and the galactic dynamo. Here we present and compare the results of two different models for the rotation of extraplanar gas: the ballistic model and hydrostatic model. In the ballistic model, interstellar clouds'' are assumed to follow ballistic trajectories, while in the hydrostatic model, rotation is determined by the combination of the gravitational potential, pressure gradients and magnetic tension. We list the principal uncertainties and predictions of both models, and observational tests to distinguish between them. We find that neither model satisfactorily matches the data available for NGC 891 and NGC 5775, and suggest possible resolutions.

The author(s) of this abstract have provided an email address for comments about the abstract: benjamin@physics.wisc.edu

Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.