HCN J=4-3, HNC J=1-0, (HCN)-C-13 J=1-0, and HC3N J=10-9 Maps of the Galactic Center Region. I. Spatially Resolved Measurements of Physical Conditions and Chemical Composition

This supplement paper presents the maps of HCN J = 4-3, HNC J = 1-0, (HCN)-C-13 J = 1-0, and HC3N J = 10-9 for the Galactic central molecular zone (CMZ), which have been obtained using the Atacama Submillimeter Telescope Experiment and Nobeyama Radio Observatory 45m telescope. Three-dimensional maps (2D in space and 1D in velocity) of the gas kinetic temperature (T-kin), hydrogen volume density (n(H2)), and fractional abundances of eight molecules (HCN, HNC, HC3N, HCO+, H2CO, SiO, CS, and N2H+) have been constructed from our and archival data. We have developed a method with hierarchical Bayesian inference for this analysis, which has successfully suppressed the artificial correlations among the parameters created by systematic errors due to the deficiency in the simple one-zone excitation analysis and the calibration uncertainty. The typical values of T-kin and n(H2) are 10(1.8) K and 10(4.2) cm(-3), respectively, and the presence of an additional cold, low-density component is also indicated. The distribution of high-temperature regions is poorly correlated with known active star-forming regions, while a few of them coincide with shocked clouds. Principal component analysis has identified two distinct groups in the eight analyzed molecules: one group with large PC1 and PC2 scores, and the other with a large T-kin dependence, which could be explained using two regimes of shock chemistry with fast (greater than or similar to 20 km s(-1)) and slow (greater than or similar to 20 km s(-1)) velocity shocks, respectively. This supports the idea that the mechanical sputtering of dust grains and the mechanical heating play primary roles in the chemical and thermal processes in CMZ clouds.