Gas in the CMZ toward the Galactic Nucleus Studied by H3 + and CO Spectra

Infrared spectroscopy of H3+ toward the Galactic center uncovered the presence of vast amount of diffuse (100 cm−3) and warm gas (250 K) filling the Central Molecular Zone of our Galaxy (CMZ; R 200 K) and moderately dense gas (200 cm−3) local in the Galactic nucleus. The absorption profiles of H3+ R(1,1)l consists of two components. The one is sharp absorption lines in the negative velocity, that represents the diffuse clouds in the foreground Galactic Arms. The other is the trough absorption spanning from −150 to +90 km s−1. The absorption profile of the trough component has detailed structure with several absorption minima, which was not noticed in the previous lower resolution ...