Dust Emission from Evolved and Unevolved H II Regions in the Large Magellanic Cloud

Abstract

We present a study of the dust properties of 12 classical and superbubble H II regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer (8, 24, 70, and 160 _ m bands), obtained as part of the Surveying the Agents of a Galaxy's Evolution (SAGE) program, along with archival spectroscopic classifications of the ionizing stars to examine the role of stellar sources on dust heating and processing. Our infrared observations show surprisingly little correlation between the emission properties of the dust and the effective temperatures or bolometric magnitudes of stars in the H II regions, suggesting that the H II region evolutionary timescale is not on the order of the dust processing timescale. We find that the infrared emission of superbubbles and classical H II regions shows little differentiation between the two classes, despite the significant differences in age and morphology. We do detect a correlation of the 24 _ m emission from hot dust with the ratio of 70-160 _ m flux. This correlation can be modeled as a trend in the temperature of a minority hot dust component, while a majority of the dust remains significantly cooler.