Molecular hydrogen along two lines of sight through the Large Magellanic Cloud

Kurt S. Gunderson, University of Colorado Boulder
Geoffrey C. Clayton, Louisiana State University
James C. Green, University of Colorado Boulder


We have remeasured the H2 column densities along lines of sight to the Large Magellanic Cloud (LMC) using spectra taken by the Hopkins Ultraviolet Telescope (HUT). Three lines of sight were analyzed using the pair method and previously determined Fitzpatrick & Massa extinction parameters to allow H2 absorption models to be fitted. Substantial improvements over the values first reported by Clayton et al. were made for two of the three lines of sight. Comparisons between LMC and Galactic environments suggest that the factors which lead to extinction curve variations (e.g., metallicity or shocks) do not affect the efficiency of H2 formation on the surfaces of the dust grains: NH2/E(B - V) values are approximately the same in both galaxies despite large differences in NH1/E(B - V).