Spatial distribution and nature of H2O masers in Messier 82

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 377 km s(-1), 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 HII 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.