The discovery of a gas-rich bar in UGC 2855: a galaxy in a pre-starburst phase?

We present the first interferometric CO observations of the barred late-typ e galaxy UGC 2855 and its companion UGC 2866. UGC 2855 is shown to belong t o the rare class of galaxies with a long (similar to 8 kpc) continuous mole cular bar. The velocity field along the bar is dominated by solid-body rota tion and shows few perturbations. This, together with an almost constant an d low (CO)-C-12/(CO)-C-13 Line intensity ratio along the bar and in the cen ter as well as only weak Her emission, indicate that the gas in the bar is not subjected to strong shocks, but surprisingly quiescent. In the central 3 ", a high velocity feature consisting of a number of Giant Molecular Asso ciations, is identified. We discuss possible scenarios of the nature of thi s structure in connection with the question of the presence of an Inner Lin dblad Resonance (ILR) in the bar. We suggest that the bar of UGC 2855 is a young object, possibly has no ILR, and that the mass concentration toward t he center of the galaxy is just beginning. In contrast, the companion UGC 2 866 experiences a strong starburst. We compare the properties of the gas in the bar of UGC 2855 to those we find in NGC 7479. Despite superficial para llels, the two bars are very dissimilar objects in terms of (CO)-C-12/(CO)- C-13 line ratio, velocity field and H alpha activity. NGC 7479 exhibits sta rburst characteristics, while we argue that UGC 2855 is in a pre-burst stag e.