AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 7. Spirals and Ellipticals
Display, Monday, May 31, 1999, 9:20am-6:30pm, Southwest Exhibit Hall

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[7.01] Near-Infrared Observations of Hotspots in the Circumnuclear Rings of NGC 2997 and NGC 6951

D.M. Elmegreen, F.R. Chromey, J.E. Sawyer (Vassar Coll.), E.L. Reinfeld (Wellesley Coll.)

Near-infrared observations of NGC 2997 and NGC 6951 with the KPNO 4-m telescope reveal complete rings of symmetrically placed star-forming complexes, some of which are obscured at optical wavelengths. The hotspot masses range from a few x 104 to a few x 105 Mo in both galaxies. The regular hotspot spacings of about 200 pc in a ring 55 pc thick in NGC 2997 and 380 pc in a ring 150 pc thick in NGC 6951 are consistent with formation by a large-scale gravitational instability in the ring. Visual extinction is estimated to be up to 3 mag around the ring in NGC 2997 and up to 5 mag in NGC 6951, as dust lanes spiral in and cross the ring. Published HST images reveal smaller super star clusters within the large complexes. These SSCs have power law luminosity functions with an exponent of approximately -2 in both galaxy rings, the same as for star-forming complexes in the disks of normal spiral galaxies.

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