9318849 Jackson Despite extensive study, the properties of molecular gas in the nuclei of external galaxies are poorly understood. Previously the molecular ISM in galaxies has been studied with CO emission, which provides the distribution and mass of molecular gas. Unfortunately, CO does not directly probe the dense molecular gas. Dense gas is particularly important because it actively forms stars and also traces the circumnuclear environment. The Principal Investigator will develop a new set of tools by observing molecules such as HCN, which require high densities for excitation. The technology is now in place to map these species in nearby galaxies at 50 pc resolution. By observing several lines he will map in detail the density, temperature, composition, and motion of the dense molecular gas in galactic nuclei. He will perform HCN surveys of a number of galaxies in order to characterize their dense gas properties.
