WAVELENGTH-DEPENDENT KINEMATICS IN THE DUSTY INCLINED GALAXY NGC-2146

We present measurements of the apparent rotation curves of the dusty inclined spiral NGC 2146 taken using conventional long-slit spectroscopy in the red and near-infrared. The curve measured in Halpha emission shows, with respect to that observed in [S III] lambda9069, a series of dips in velocity which coincide in positions with dips in the intensity of Halpha, and with the dust lanes evident in broad band images. A more detailed quantitative comparison, including a previously published velocity curve in Brgamma (Hutchings et al. 1990), using a schematic model, supports the hypothesis that dust is causing the Halpha/[S III] discrepancies and highlights the need to measure rotation curves of inclined galaxies as far into the infrared as techniques permit. The lambda9069 [S III] emission reveals a zone in expansion at 190 pc from the nucleus (previously detected in Brgamma but at lower spectral resolution and with consequently limited velocity diagnostics) whose kinematics and energetics are well explained in terms of an expanding ''superbubble'' due to a starburst. Finally we suggest, from the invariance of the velocity curve with wavelength at nucleocentric radii greater than approximately 1500 pc that our observations imply very limited observable dust extinction in the outer parts of the disk of NGC 2146.