We describe the results of a long-slit spectroscopic study of an unusual star complex in the nearby spiral galaxy NGC 6946 using the SAO 6 m telescope and the Keck 10 m telescope .
The complex resembles a circular bubble 600 pc in diameter with a young super star cluster ( SSC ) near the center .
The kinematics of ionized gas is studied through H \alpha emission with several slit positions .
Position–velocity diagrams show two distinct features with high speed motions .
One is an irregularly shaped region to the east of the SSC , 270 pc in size , in which most of the H \alpha emission is blue shifted by 120 km s ^ { -1 } , and another is a 350 pc shell centered on the SSC with positive and negative velocity shifts of 60 km s ^ { -1 } .
Balmer and \ion Hei absorption lines in the SSC give an age of 12 - 13 Myr , which is consistent with the photometric age but significantly older than the kinematic ages of the high speed regions .
The energetics of the SSC and its interaction with the environment are considered .
The expansion energies exceed 10 ^ { 52 } ergs , but the power outputs from winds and supernova in the SSC are large enough to account for this .
The intensities of Balmer , [ \ion Nii ] , and [ \ion Sii ] emission lines within and around the complex indicate that shock excitation makes a significant contribution to the emission from the most energetic region .