AAS 207th Meeting, 8-12 January 2006
Session 164 Extra-galactic ISM - Near to Far
Oral, Wednesday, 2:00-3:30pm, January 11, 2006, Balcony A

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[164.05] Kinematics of the Diffuse Ionized Gas Halos of NGC 891 and NGC 5775

G. H. Heald, R. J. Rand (University of New Mexico), R. A. Benjamin (University of Wisconsin - Whitewater), M. A. Bershady (University of Wisconsin - Madison), J. A. Collins (University of Colorado - Boulder), J. Bland-Hawthorn (Anglo-Australian Observatory)

As part of an ongoing effort to characterize the nature of the disk-halo interaction in spiral galaxies, we present an investigation into the kinematics of the diffuse ionized gas (DIG) halos of two edge-on spirals, NGC 891 and NGC 5775. Observations of optical emission lines were obtained at high spectral resolution with the SparsePak fiber array at WIYN, and the TAURUS-II Fabry-Perot interferometer at the AAT, respectively. Detailed three-dimensional models of the galaxies were created and compared with the data, revealing the presence of a vertical gradient in rotational velocity in each case. The sense of the gradient corresponds to decreasing rotation speed with increasing height above the disk; the magnitude is approximately 15 km s-1 kpc-1 in NGC 891, and 8 km s-1 kpc-1 in NGC 5775. Qualitatively, this behavior is predicted by models of the disk-halo interaction which consider gas being lifted out of the disk, but quantitative agreement has not yet been achieved. We describe the results of our observations, present a comparison with a purely ballistic model of disk-halo flow, and discuss prospects for a better understanding of this critical process in the evolution of galaxies.

This material is based on work partially supported by the National Science Foundation under Grant No. AST 99-86113.

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