The AMANOGAWA-2SB Galactic Plane Survey I. Data on the Galactic Equator

Using a waveguide-type sideband-separating receiver (2SB receiver) on the Tokyo-NRO 60-cm telescope (renamed the AMANOGAWA telescope), we carried out simultaneous observations in the (CO)-C-12 (J = 2-1) and (CO)-C-13 (J = 2-1) lines over the galactic plane l = 10 degrees-245 degrees along b = 0 degrees with a 3.'75 grid. Using the (CO)-C-12 (J = 1-0) data of Dame et al. (2001, ApJ, 547,792), who used a beam size almost the same as ours, we show (CO)-C-12 (J = 2-1)/(CO)-C-12 (J = 1-0) and (CO)-C-13 (J = 2-1)/(CO)-C-12 (J = 2-1) intensity ratios on the l-v map and the intensity correlations among the (CO)-C-12 (J = 2-1), (CO)-C-13 (J = 2-1), and (CO)-C-12 (J = 1-0) lines. As a result, a linear correlation between (CO)-C-12 (J = 2-1) and (CO)-C-12 (J = 1-0) and a curved correlation between (CO)-C-12 (J = 2-1) and (CO)-C-13 (J = 2-1), as produced by most of the data, have been found. We investigated these correlations with simple radiative transfer equations to ascertain a number of restrictions on the physical quantities of molecular gas on a galactic scale.