Dense Molecular Clouds in the Galactic Center Region. I. Observations and Data

We have observed a 160' × 40' (l × b) region around the Galactic center in the CS J=1-0 line with a high spatial resolution and high sensitivity using the 45 m telescope at Nobeyama Radio Observatory. The observed area includes the Sgr A radio arc complex, Sgr B, Sgr C, and Sgr D. About 24,000 spectra of CS J = 1-0 emission, which is a good tracer of high-density (n ≅ 104 cm-3) molecular clouds, were obtained. The observed data are presented in l-b, l-v, and b-v maps. The total CS line flux in this area is ∫ S dv = 1.1 × 106 Jy km s-1. Typical optical thickness of C32S J = 1-0 emission is equal to or lower than τ=2-3. The total molecular mass in the Galactic center region is estimated to be M(H2) = (3-8) × 107 M☉ from the assumption of LTE. One-third of the molecular clouds in the Galactic center region are involved in several continuous curved ridges extended along the Galactic longitude. The most prominent ridge has a "bow"-like structure with a length of 300 pc.