1997A&A...317..548C

Nine HII regions of the LMC were mapped in ¹³CO(1-0) and three in ¹²CO(1-0) to study the physical properties of the interstellar medium in the Magellanic Clouds. For N113 the molecular core is found to have a peak position which differs from that of the associated HII region by 20". Toward this molecular core the ¹²CO and ¹³CO peak T_MB line temperatures of 7.3K and 1.2K are the highest so far found in the Magellanic Clouds. The molecular concentrations associated with N113, N44BC, N159HW, and N214DE in the LMC and LIRS36 in the SMC were investigated in a variety of molecular species to study the chemical properties of the interstellar medium. I(HCO⁺)/I(HCN) and I(HCN)/I(HNC) intensity ratios as well as lower limits to the I(¹³CO)/I(C¹⁸O) ratio were derived for the rotational 1-0 transitions. Generally, HCO⁺ is stronger than HCN, and HCN is stronger than HNC. The high relative HCO⁺ intensities are consistent with a high ionization flux from supernovae remnants and young stars, possibly coupled with a large extent of the HCO⁺ emission region. The bulk of the HCN arises from relatively compact dense cloud cores. Warm or shocked gas enhances HCN relative to HNC. From chemical model calculations it is predicted that I(HCN)/I(HNC) close to one should be obtained with higher angular resolution (≲30") toward the cloud cores. Comparing virial masses with those obtained from the integrated CO intensity provides an H₂ mass-to-CO luminosity conversion factor of 1.8x10²⁰mol/cm²(K.km/s)^–1 for N113 and 2.4x10²⁰mol/cm²(K.km/s)^–1 for N44BC. This is consistent with values derived for the Galactic disk.