MOLECULAR ABUNDANCES IN THE MAGELLANIC CLOUDS .1. A MULTILINE STUDY OF 5 CLOUD CORES

Nine H II regions of the LMC were mapped in (CO)-C-13(1-0) and three i n (CO)-C-12(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 H II region by 20 ''. Toward this molecular core the (CO)-C-12 and (CO)-C- 13 peak T-MB line temperatures of 7.3 K and 1.2 K are the highest so f ar found in the Magellanic Clouds. The molecular concentrations associ ated with N113, N44BC, N159HW, and N214DE in the LMC and LIRS 36 in th e 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((CO)-C-1 3)/I((CO)-O-18) ratio were derived for the rotational 1-0 transitions. Generally, HCO+ is stronger than HCN, and HCN is stronger than HNC. T he high relative HCO+ intensities are consistent with a high ionizatio n flux from supernovae remnants and young stars, possibly coupled with a large extent of the HCO+ emission region. The bulk of the HCN arise s from relatively compact dense cloud cores. Warm or shocked gas enhan ces HCN relative to HNC. From chemical model calculations it is predic ted that I(HCN)/I(HNC) close to one should be obtained with higher ang ular resolution (less than or similar to 30 '') toward the cloud cores . Comparing virial masses with those obtained from the integrated CO i ntensity provides an H-2 mass-to-CO luminosity conversion factor of 1. 8 x 10(20) mol cm(-2) (K km s(-1))(-1) for N113 and 2.4 x 10(20) mol c m(-2) (K km s(-1))(-1) for N44BC. This is consistent with values deriv ed for the Galactic disk.