EXTRAPLANAR EMISSION-LINE GAS IN NGC-891

We have used spectroscopy and high-resolution imaging to study the disk-halo interaction in the edge-on spiral galaxy NGC 891, which is known to have extraplanar gas. Halpha imaging of the northeast side of this galaxy reveals diffuse emission-line gas both above and below the plane, as well as new bubble-like structures on 0.5-1 kpc scales emerging from the disk. The diffuse emission is best modeled in the radial direction as a disk of constant emission measure with a sharp cutoff. Long-slit spectroscopy of the Halpha line within 2.4 kpc of the galaxy's plane shows departures from the velocity structure found in a model with strict corotation. The departures from corotation range up to 40 km s-1, consistent with galactic fountain theory.