2000A&A...362...42A

High resolution OVRO aperture synthesis maps of the ¹²CO 1-0 emission in the ``Medusa'' galaxy merger (NGC 4194) reveal the molecular emission being surprisingly extended. The ¹²CO emission is distributed on a total scale of 25'' (4.7 kpc) – despite the apparent advanced stage of the merger. The complex, striking ¹²CO morphology occupies mainly the center and the north-eastern part of the main optical body. The extended ¹²CO flux is tracing two prominent dust lanes: one which is crossing the central region at right angle (with respect to the optical major axis) and a second which curves to the north-east and then into the beginning of the northern tidal tail. The bulk of the ¹²CO emission (67%) can be found in a complex starburst region encompassing the central 2kpc. The molecular gas is distributed in five major emission regions of typical size 300pc. About 15% of the total ¹²CO flux is found in a bright region 1.5'' south of the radio continuum nucleus. We suggest that this region together with the kpc sized central starburst is being fueled by gas flows along the central dust lane. We discuss the merger history of NGC 4194 and suggest that it may be the result of a early-type/spiral merger with a shell emerging to the south of the center. The total molecular mass in the system is estimated to be at most 2x10⁹M_☉, depending on which ¹²CO - H₂ conversion factor is applicable. The high ¹²CO/¹³CO 1-0 intensity ratio, ≃20, indicates highly excited physical conditions in the interstellar medium showing that the starburst has a big impact on its surrounding ISM. At the current rate of star formation, the gas will be consumed within 40 million years.