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

TL;DR

This study investigates dust properties in 12 HII regions of the Large Magellanic Cloud using infrared data, revealing minimal correlation between dust emission and stellar properties, and identifying a hot dust component linked to specific flux ratios.

Contribution

It provides new insights into dust heating and processing in HII regions, showing little difference between evolved and unevolved regions despite age and morphology variations.

Findings

Little correlation between dust emission and stellar temperature or luminosity.

Infrared emission is similar in both classical and superbubble HII regions.

A hot dust component correlates with the 70/160 μm flux ratio, indicating temperature variations.

Abstract

We present a study of the dust properties of 12 classical and superbubble HII regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer (8, 24, 70, and 160 \mum 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 HII regions, suggesting that the HII region evolutionary timescale is not on the order of the dust processing timescale. We find that the infrared emission of superbubbles and classical HII regions shows little differentiation between the two classes, despite the significant differences in age and morphology. We do detect a correlation of the 24 \mum emission from hot dust with the ratio of 70 to 160 \mum 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.