The Near-Infrared Extinction Law in Regions of High Av

Abstract

We present a spectroscopic study of the shape of the dust-extinction law between 1.0 and 2.2um towards a set of nine ultracompact HII regions with Av > 15 mag. We find some evidence that the reddening curve may tend to flatten at higher extinctions, but just over half of the sample has extinction consistent with or close to the average for the interstellar medium. There is no evidence of extinction curves significantly steeper than the standard law, even where water ice is present. Comparing the results to the predictions of a simple extinction model, we suggest that a standard extinction law implies a robust upper limit to the grain-size distribution at around 0.1 - 0.3um. Flatter curves are most likely due to changes in this upper limit, although the effects of flattening due to unresolved clumpy extinction cannot be ruled out.

arXiv comment9 pages, 7 figures

References in corpus (8)

• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• ISO spectroscopy of compact HII regions in the Galaxy. II Ionization and elemental abundances
• Direct Observations of the Ionizing Star in the UC HII Region G29.96-0.02: A Strong Constraint on the Stellar Birth Line for Massive Stars
• A photoionization model of the compact HII region G29.96-0.02
• A Near-Infrared Imaging Survey of Coalsack Globule 2
• Near Infrared Spectroscopy of the Ultracompact HII region G45.12+0.13
• Gemini Mid-Infrared Imaging of Massive Young Stellar Objects in NGC 3576
• [Ne II] 12.8 Micron Images of Four Galactic Ultracompact H II Regions: Ionized Neon Abundance as a Tracer of the Ionizing Stars

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