Molecular clouds in the 30 Doradus halo

A deep survey was made of the CO(1-0) line emission at an angular resolution of 0.125 deg and a sensitivity in radiation temperature of 0.02 K, from a 1.0 x 0.75 deg region of the LMC centered near the 30 Doradus nebula. The CO emission is found to arise from six well-discernable molecular clouds with radii between 60 and 160 pc. The observed CO brightness temperatures are very weak about 0.1 K or about 20 time lower than that expected from a typical Galactic GMC if located in the LMC. The CO luminosities of these clouds, ranging between 10,000 and 60,000 K km/s/sq pc, are considerably lower than that of Galactic clouds of the same size. The CO luminosity of the 30 Doradus halo clouds are typically about 15 times fainter than that of Galactic cloud with similar line widths. The N(H2 + 2H)/I(CO) conversion factor for the 30 Doradus halo clouds, determined assuming that they are virialized, is about 13 times larger than the value for the inner Galaxy and about two times larger than the LMC average value. The relation between the virial mass and CO luminosity for the Doradus clouds is different from that for Galactic clouds. (AIAA)