Correcting for the Effects of Interstellar Extinction

TLDR

Extinction wavelength dependence is tightly constrained and correlates with interstellar environment. The paper seeks the optimal method to correct astronomical data for Galactic interstellar extinction. The authors review extinction features across IR–UV, discuss dereddening strategies and uncertainties, and present a new derivation of the average Galactic extinction curve and its dependence on R. The study shows a wide range of Galactic extinction properties, especially in the UV, and provides curves that accurately represent monochromatic extinction for dereddening across IR–UV and for deriving photometric extinction relations.

Abstract

This paper addresses the issue of how best to correct astronomical data for the wavelength-dependent effects of Galactic interstellar extinction. The main general features of extinction from the IR through the UV are reviewed, along with the nature of observed spatial variations. The enormous range of extinction properties found in the Galaxy, particularly in the UV spectral region, is illustrated. Fortunately, there are some tight constraints on the wavelength dependence of extinction and some general correlations between extinction curve shape and interstellar environment. These relationships provide some guidance for correcting data for the effects of extinction. Several strategies for dereddening are discussed along with estimates of the uncertainties inherent in each method. In the Appendix, a new derivation of the wavelength dependence of an average Galactic extinction curve from the IR through the UV is presented, along with a new estimate of how this extinction law varies with the parameter R = A(V)/E(B-V). These curves represent the true monochromatic wavelength dependence of extinction and, as such, are suitable for dereddening IR--UV spectrophotometric data of any resolution, and can be used to derive extinction relations for any photometry system.