Physical Conditions in the LMC’s Quiescent Molecular Ridge: Fitting Non-LTE Models to CO Emission

The Molecular Ridge in the LMC extends several kiloparsecs south from 30 Doradus, and it contains ∼30% of molecular gas entire galaxy. However, southern end is quiescent—it almost no massive star formation, which a dramatic decrease very active massive-star-forming regions N159, N160. We present new Atacama Large Millimeter/submillimeter Array Pathfinder Experiment observations at resolution as high ∼16'' (∼3.9 pc) with lines 12CO(1-0), 13CO(1-0), 12CO(2-1), 13CO(2-1), CS(2-1). analyze these emission our multiline non-LTE fitting tool to produce maps Tkin, , NCO across region based on models RADEX. Using simulated data for range parameter space each variables, we evaluate how well method can recover physical parameters given set lines. then compare results this LTE XCO methods obtaining mass estimates line ratios correspond conditions. find that allows us more directly probe conditions estimate values are less subject effects optical depth line-of-sight projection than previous methods. fitted show strong correlation presence young stellar objects (YSOs), total average associated YSOs. Typical formation diagnostics, such mean density, dense fraction, virial do not YSO properties.