Spatially Resolved Chemistry in Nearby Galaxies II. The Nuclear Bar in
  Maffei 2
  We present 2" - 10" imaging of eleven transitions from nine molecular species
across the nuclear bar in Maffei 2. The data were obtained with the BIMA and
OVRO interferometers. The ten 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
principle 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 argue 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 C2H line, suggesting that this ratio may be a powerful new dense
photon-dominated region (PDR) probe in external galaxies. C2H reveals a
molecular outflow along the minor axis. The morphology and kinematics of the
outflow are consistent with an outflow age of 6-7 Myrs.
