Components of the diffuse ultraviolet radiation at high latitudes

Abstract

We have used data from the Galaxy Evolution Explorer to study the different components of the diffuse ultraviolet background in the region between the Galactic latitudes 70◦–80◦. We find an offset at zero dust column density (E(B − V) = 0) of 240 ± 18 photon units in the FUV (1539 Å) and 394 ± 37 photon units in the NUV (2316 Å). This is approximately half of the total observed radiation with the remainder divided between an extragalactic component of 114 ± 18 photon units in the FUV and 194 ± 37 photon units in the NUV and starlight scattered by Galactic dust at high latitudes. The optical constants of the dust grains were found to be a = 0.4 ± 0.1 and g = 0.8 ± 0.1 (FUV) and a = 0.4 ± 0.1 and g = 0.5 ± 0.1 (NUV). We cannot differentiate between a Galactic or extragalactic origin for the zero-offset but can affirm that it is not from any known source.