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 ≅ 10 4 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 × 10 6 Jy km s -1 . Typical optical thickness of C 32 S 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 (H 2 ) = (3-8) × 10 7 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.