Dense gas in the bulges of external galaxies

In order to probe the physical conditions in the high-pressure environments of galactic bulges, we have studied the properties of the dense molecular gas in the bulges of a sample of 19 mostly normal spiral galaxies. We observed the 3 mm emission from the molecules HCN and CS, which trace gas densities of ∼10 5 cm -3 . Our high detection rate (68% in HCN, 50% in CS) suggests that most spiral galaxies, not just starburst galaxies, contain appreciable quantities of dense gas in their bulges