AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 6. Interactions, Mergers and Starbursts
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[6.07] A Warped Inner Disk in the Starburst Galaxy NGC 7552

C. A. Tremonti (Johns Hopkins University), D. Calzetti (Space Telescope Science Institute)

We report the discovery of a warped inner disk in the nearly face-on nearby starburst galaxy NGC 7552. Velocities in the inner 2.7' (15.3 kpc) of the galaxy were mapped by placing a long slit through the galaxy nucleus and rotating it through eight position angles. The spectra were centered on H-alpha and had a velocity resolution of ~25 km/s. Detailed velocity maps were constructed of the inner 1.6 kpc of the galaxy. In this region the sampling was sufficient that structures seen in a ground based H-alpha image were well reproduced by a map of the H-alpha intensity. The H-alpha intensity shows a relatively sharp fall off at a radius of ~500 pc, defining a distinct inner disk which is also seen in an archival WFPC2 606W snapshot image. This inner disk marks the extent of the solid body rotation curve. Inside this region, isovelocity contours exhibit a marked twisting as the position angle of the galaxy minor axis rotates by approximately 45 degrees.

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