A survey for extragalactic HCN and HCO

We have surveyed 15 galaxies for HCN and HCO + J=1→0 emission and detected HCN in 12 objects and HCO + in 11. Maps were made of IC 342, M51, and M83. Since the HCN and HCO + lines require higher densities than CO J=1→0 for excitation, they probe denser gas. Strong HCO + J=3→2 emission has been found in NGC 253. Our new J=1→0 detections along with the J=3→2 data are used to estimate excitation temperatures and optical depths