LARGE-SCALE MOLECULAR SHOCKS IN STARBURST AND ACTIVE GALAXIES

Large-scale shocks propagate in die interstellar medium of, starburst, and active galaxies, driven by the same mechanisms that regulate the evolution of the star formation and AGN episodes. The imprints of shocks in the chemical composition of the molecular gas provide useful means to identify those mechanisms and to asses their effects. We review some recent, and on-going studies Of the molecular gas chemistry in the nearby star-forming galaxies IC 342, NGC 253 and M 82, based on the well known shock tracer silicon monoxide (SiO). When mapped at high-spatial resolution the SiO emission reveals substantial differences among these galaxies. In particular, the location of shocks and their dominant driver are ill correspondence With the evolutionary stage of the starburst episode. complementary observations of other tracers of shock chemistry, like methanol (CH3OH), help its to improve the characterization of the shock mechanisms. We also Present the first high-resolution observations of the SiO emission in the Seyfert 2 galaxy NGC 1068.