AMANOGAWA-2SB survey: a northern galactic plane survey in 12CO (J = 2 - 1) and 13CO (J = 2 - 1) with the Amanogawa telescope

We performed ¹²CO(J = 2 - 1) and ¹³CO(J = 2 - 1) line surveys of the galactic plane using the AMANOGAWA telescope (Nakajima et al. 2007) which covers 5° ≤ l ≤ 180° on a 7'.5 grid. The telescope beamsize and velocity resolution are 8.7' ± 0.4' and 1.3 km s^-1. The resultant rms noise level is typically 0.12 K in T _A*. We found a linear correlation between ¹²CO(J = 2 - 1) and ¹²CO(J = 1 - 0) and a curved correlation between ¹²CO(J = 2 - 1) and ¹³CO (J = 2 - 1), although the intensity ratios of these three lines have intrinsic variation. These correlations can be reproduced with simple radiative transfer equations suggesting some restrictions on the physical quantities of molecular gas on a galactic scale.