2012ApJ...755..104M

We present 2''-10'' imaging of 11 transitions from 9 molecular species across the nuclear bar in Maffei 2. The data were obtained with the BIMA and OVRO interferometers. The 10 detected transitions are compared with existing CO isotopologues, HCN, CS, and millimeter continuum data. Dramatic spatial variations among the mapped species are observed across the nuclear bar. A principal component analysis is performed to characterize correlations between the transitions, star formation, and molecular column density. The analysis reveals that HCN, HNC, HCO⁺, and 3 mm continuum are tightly correlated, indicating a direct connection to massive star formation. We find two main morphologically distinct chemical groups, CH₃OH, SiO, and HNCO comprising the grain chemistry molecules, versus HCN, HNC, HCO⁺, and C₂H, molecules strong in the presence of star formation. The grain chemistry molecules, HNCO, CH₃OH, and SiO, trace hydrodynamical bar shocks. The near constancy of the HNCO/CH₃OH, SiO/CH₃OH, and SiO/HNCO ratios argues that shock properties are uniform across the nucleus. HCN/HCO⁺, HCN/HNC, HCN/CS, and HCN/CO ratios are explained primarily by variations in density. High HCO⁺/N₂H⁺ ratios are correlated with the C₂ H line, suggesting that this ratio may be a powerful new dense photon-dominated region probe in external galaxies. C₂ H reveals a molecular outflow along the minor axis. The morphology and kinematics of the outflow are consistent with an outflow age of 6-7 Myr.