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Comparative study of the relationships between CO isotopic luminosities and infrared luminosity for the Galactic dense cores

Combining the 12CO(1-0), 13CO(1-0), and C18O(1-0) data with IRAS four band data, we here estimate the physical parameters such as size, viral mass, and CO J=1-0 isotopic and infrared luminosities for 29 dense molecular clouds from two published CO samples. We further analyze the various correlations between CO J=1-0 isotopic luminosities and infrared luminosity (star formation rate, SFR) and discuss the relationships between the molecular gas tracers and SFR. The results show that 12CO(1-0), 13CO(1-0) and C18O(1-0) luminosities have tight correlations with each other. CO J=1-0 isotopic luminosities and SFR show weak correlations with lager scatter than the HCN-IR correlations of 47 dense cores in the Galaxy and 65 external star-forming galaxies. This might be interpreted as that both the SFR and star formation efficiency are mainly determined by the molecular gas at high volume density rather than high column density.