%0 Journal Article
%T An Empirical Relation between Sodium Absorption and Dust Extinction
%A Dovi Poznanski
%A J. Xavier Prochaska
%A Joshua S. Bloom
%J Physics
%D 2012
%I arXiv
%R 10.1111/j.1365-2966.2012.21796.x
%X Dust extinction and reddening are ubiquitous in astronomical observations and are often a major source of systematic uncertainty. We present here a study of the correlation between extinction in the Milky Way and the equivalent width of the NaI D absorption doublet. Our sample includes more than 100 high resolution spectra from the KECK telescopes and nearly a million low resolution spectra from the Sloan Digital Sky Survey (SDSS). We measure the correlation to unprecedented precision, constrain its shape, and derive an empirical relation between these quantities with a dispersion of order 0.15 magnitude in E(B-V). From the shape of the curve of growth we further show that a typical sight line through the Galaxy, as seen within the SDSS footprint, crosses about three dust clouds. We provide a brief guide on how to best estimate extinction to extragalactic sources such as supernovae, using the NaI D absorption feature, under a variety of circumstances.
%U http://arxiv.org/abs/1206.6107v2