THE KINEMATICS OF THE IONIZED AND MOLECULAR-HYDROGEN IN THE STARBURSTGALAXY NGC-253

Near-infrared H-2 1-0 S(1) and Br gamma velocity curves along the majo r axis of NGC 253 have revealed a central velocity gradient that is 7 times steeper than that shown by the optical velocity curve. This is i nterpreted as an optical depth effect due to dust. Approximately 35 ma g of visual extinction in the center is required to match the southwes t side of the optical velocity curve. The spatial variation of the rat io of these lines to the (CO)-C-12 (J = 1 --> 0) line is compared amon g starburst galaxies NGC 253, M82, and NGC 4945 to investigate the exc itation mechanism responsible for the H-2 1-0 S(1) line.