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

Kunihiko Tanaka, Makoto Nagai, Kazuhisa Kamegai, Takahiro Iino, Takeshi Sakai

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This supplement paper presents the maps of HCN J = 4-3, HNC J = 1-0, 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 45 m telescope. Three-dimensional maps (2D in space and 1D in velocity) of the gas kinetic temperature (T kin), hydrogen volume density (nH2), and fractional abundances of eight molecules (HCN, HNC, , HCO+, H2CO, SiO, CS, and ) 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 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 T kin dependence, which could be explained using two regimes of shock chemistry with fast (≳20 km s-1) and slow (≳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.

Original languageEnglish
Article number40
JournalAstrophysical Journal, Supplement Series
Issue number2
Publication statusPublished - 2018 Jun


  • Galaxy: center
  • ISM: molecules

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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