NGC 2146's starburst region and extended structure

We present mm-wavelength and optical observations of the starburst region in NGC 2146. This region of ∼4 kpc diameter contains a well-ordered distribution of stars, gas, and dust, and a well-ordered rotation. The possible anomalies found in our observation are a warped CO distribution and an increase in the CO line width at the NW edge of the starburst region. The investigation of a possible encounter or merger origin of the starburst may therefore have to concentrate on the distorted outer structure of the galaxy. There are three large-scale features of ∼20 kpc extent, two of which give the impression of being stellar sub-systems. The third feature is an incomplete and expanding ring of H ii regions and stars, apparently indicating an event that occurred some 300 Myr ago.