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Aromatic Features in M101 HII Regions and Starburst Galaxies

Karl D. Gordon·C. W. Engelbracht·J. -D. T. Smith·G. H. Rieke·K. A. Misselt
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Abstract

The behavior of the aromatic features as a function of metallicity/radiation field hardness in M101 HII regions and starburst galaxies is investigated using Spitzer/IRS spectra. These spectra reveal that the 6.2, 7.8+8.6, and 11.3 micron aromatics have different dependencies on metallicity/radiation field hardness. Specifically, the 6.2 and 7.8+8.6 micron aromatics are weak or absent at a metallicity, 12+log(O/H), of approx. 8.0 while the 11.3 micron feature remains relatively strong. These results apply to both the M101 HII regions and starbursts showing that HII regions can indeed be thought of as ``mini-starbursts.'' Comparison of this work with various candidate materials results in a good match with the annealing behavior in Quenched Carbonaceous Composite (QCC) which is an amorphous, hydrogenated, carbonaceous solid.

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Karl D. Gordon, C. W. Engelbracht, J. -D. T. Smith, G. H. Rieke, K. A. Misselt. 2006-05-22. Aromatic Features in M101 HII Regions and Starburst Galaxies. https://arxiv.org/abs/astro-ph/0605544

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