Abstract

We have analyzed the distributions of CO and temperature in a large suite of simulated molecular clouds, in order to help us understand how to interpret CO line emission from real molecular clouds. We find that most of the CO is located at densities over 103cm-3 where the temperature is roughly 10–20 K independently of the mean density, metallicity and UV field strength. Although, most of the volume is in warmer and thinner regions where CO abundance is small. On that account, CO observations alone give a misleading view of the physical conditions in the clouds.