Ultraviolet Extinction at High Galactic Latitudes II: The Ultraviolet Extinction Function

Abstract: We present a dust-column--dependent extinction curve parameters for ultraviolet wavelengths at high Galactic latitudes. This extinction function diverges from previous work in that it takes into account the results of Peek & Schiminovich 2013 (Paper I), which demonstrated that there is more reddening in the GALEX bands than would be otherwise expected for E(B-V) < 0.2. We also test the biases in the Planck and SFD extinction maps, and find that the SFD extinction maps are significantly biased at E(B-V) < 0.2. We find that while an extinction function that that takes into account a varying R_FUV with E(B-V) dramatically improves our estimation of FUV-NUV colors, a fit that also includes HI column density dependence is superior. The ultraviolet extinction function we present here follows the model of Fitzpatrick 1999, varying only the amplitude of the FUV rise parameter to be consistent with the data.