Astrophys. J., Suppl. Ser., 236, 40-40 (2018/June-0)
HCN J = 4-3, HNC J = 1-0, H13CN J = 1-0, and HC3N J = 10-9 maps of the Galactic Center region. I. Spatially resolved measurements of physical conditions and chemical composition.
TANAKA K., NAGAI M., KAMEGAI K., IINO T. and SAKAI T.
Abstract (from CDS):
This supplement paper presents the maps of HCN J = 4-3, HNC J = 1-0, H13CNJ = 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 45 m telescope. Three-dimensional maps (2D in space and 1D in velocity) of the gas kinetic temperature (Tkin), hydrogen volume density (nH2_), 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 Tkin and nH2_ are 101.8 K and 104.2 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 Tkin dependence, which could be explained using two regimes of shock chemistry with fast (≳20 kms–1) and slow (≲20 kms–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.
© 2018. The American Astronomical Society. All rights reserved.
Galaxy: center - ISM: molecules
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