A Reanalysis of the Ultraviolet Extinction from Interstellar Dust in the Large Magellanic Cloud

Abstract

We have reanalyzed the Large Magellanic Cloud's (LMC) ultraviolet (UV) extinction using data from the IUE final archive. Our new analysis takes advantage of the improved signal-to-noise ratio of the IUE NEWSIPS reduction, the exclusion of stars with very low reddening, the careful selection of well-matched comparison stars, and an analysis of the effects of Galactic foreground dust. Differences between the average extinction curves of the 30 Dor region and the rest of the LMC are reduced compared with previous studies. We find that there is a group of stars with very weak 2175 A bumps that lie in or near the region occupied by the supergiant shell, LMC 2, on the southeast side of 30 Dor. The average extinction curves inside and outside LMC 2 show a very significant difference in 2175 A bump strength, but their far-UV extinctions are similar. While it is unclear whether or not the extinction outside the LMC 2 region can be fitted with the relation of Cardelli, Clayton, & Mathis (CCM), sight lines near LMC 2 cannot be fitted with CCM because of their weak 2175 A bumps. While the extinction properties seen in the LMC lie within the range of properties seen in the Galaxy, the correlations of UV extinction properties with environment seen in the Galaxy do not appear to hold in the LMC.