Published online by Cambridge University Press: 25 November 2011
We have analyzed the distributions of CO and temperature in a large suite of simulatedmolecular clouds, in order to help us understand how to interpret CO line emission fromreal molecular clouds. We find that most of the CO is located at densities over103cm-3 where the temperature is roughly 10–20 K independently ofthe mean density, metallicity and UV field strength. Although, most of the volume is inwarmer and thinner regions where CO abundance is small. On that account, CO observationsalone give a misleading view of the physical conditions in the clouds.