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We present fully sampled ~3' resolution images of the 12CO(J=2-1),13CO(J=2-1), and C18O(J=2-1) emission taken with the newly developed 1.85-mmm-submm telescope toward the entire area of the Orion A and B giant molecularclouds. The data were compared with the J=1-0 of the 12CO, 13CO, and C18O datataken with the Nagoya 4-m telescope and the NANTEN telescope at the sameangular resolution to derive the spatial distributions of the physicalproperties of the molecular gas. We explore the large velocity gradientformalism to determine the gas density and temperature by using the linecombinations of 12CO(J=2-1), 13CO(J=2-1), and 13CO(J=1-0) assuming uniformvelocity gradient and abundance ratio of CO. The derived gas density is in therange of 500 to 5000 cm-3, and the derived gas temperature is mostly in therange of 20 to 50 K along the cloud ridge with a temperature gradient dependingon the distance from the star forming region. We found the high-temperatureregion at the cloud edge facing to the HII region, indicating that themolecular gas is interacting with the stellar wind and radiation from themassive stars. In addition, we compared the derived gas properties with theYoung Stellar Objects distribution obtained with the Spitzer telescope toinvestigate the relationship between the gas properties and the star formationactivity therein. We found that the gas density and star formation efficiencyare well positively correlated, indicating that stars form effectively in thedense gas region.

Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O