Milky Way Optical and Mid-Infrared Extinction Curves

Milky Way Optical and Mid-Infrared Extinction Curves

Interstellar dust extinction in the optical and mid-infrared (MIR)
wavelength ranges is characterized by an overall decreasing extinction
with increasing wavelength with superimposed broad extinction
features. I will present work focused on measuring the spectroscopic
dust extinction in these two wavelength ranges. The first study gives
the first truly spectroscopic measurement of the diffuse ISM MIR
extinction based on a sample of sightlines observed by the Spitzer
Space Telescope. This new measurement provides the full 5-40 micron
average extinction curve including profiles for the the two silicate
grain diagnostic features at 10 and 20 microns. The second study
uses HST/STIS spectra to perform the first systematic spectroscopic
study of optical extinction in the Milky Way. This study has revealed
that the Very Broad Structure in optical extinction is due to three
broad extinction features, two of which have strengths that
intriguingly correlate with the 2175 A extinction feature. The
results of these two studies provide new constraints on dust grain
properties and empirical averages useful for modeling and/or
correcting for the effects of dust extinction on background sources.

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Karl Gordon

July 17, 2019
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