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F. Walter (Caltech), A. Heithausen (University of Bonn)
We present the first high resolution observations of molecular gas in the tidal arms near NGC\,3077 (member of the M\,81 triplet) obtained at the OVRO millimeter array. The observations are centered on a region where we recently detected molecular gas in the CO (J=1-0) and (2-1) transitions using the IRAM 30m telescope. The molecular gas is extended over several kpc and is situated far outside NGC\,3077. The CO emission can be separated into at least 3 distinct complexes with equivalent radii between 250\,pc and 700\,pc. Mass estimates based on virialization and employing an XCO factor yield a total mass for the complexes of order 4\times107\,Msun i.e. more than the estimated molecular mass within NGC\,3077 itself. This implies that interactions between galaxies can efficiently remove heavy elements and molecules from a galaxy and enrich the intergalactic medium. A comparison of the distribution of HI and CO shows no clear correlation. HI masses for the molecular complexes mapped are of the same order as the corresponding molecular masses. Based on the morphology and the line widths of the CO and the HI we conclude that the complexes are gravitationally stable and have formed in situ. Since the complexes have all the ingredients to form stars in the future, we are thus perhaps witnessing the birth of a tidal dwarf galaxy. This formation process may have been important at larger look-back times where galaxy-galaxy interactions were more frequent.