1996A&A...316..188B

We have mapped the distribution of 22 GHz H₂O masers in the nuclear region of M 82 where enhanced star formation and bright molecular clouds are observed. We have used different configurations of the Very Large Array interferometer and detected H₂O emission with the C configuration. We have covered the velocity range 63 to 377km/s, and four, most likely six, H₂O maser centers have been identified. In five other directions lying along the major axis of M 82, four H₂O features have been marginally detected. Two of the detected H₂O sources coincide within the uncertainties with two well known OH masers. These H₂O sources are closely associated with two continuum sources which seem to be giant H II regions or clusters of compact H II regions. All of the H₂O sources coincide with, or lie in the immediate vicinity of dense molecular complexes mapped with the IRAM interferometer. The H₂O masers in M 82 have general properties quite similar to those of our Galaxy, and in this respect M 82 is not an outstanding galaxy. Isotropic luminosity, time variability and spatial distribution of H₂O sources are not markedly different from what is observed in the Galaxy. We believe that the H₂O masing centers observed in M 82 mark sites of current star formation, whereas the supernova remnants mark a more advanced stage of stellar evolution and apparently lie at the periphery of the molecular clouds.