ABSTRACT. We have observed a region of nebulosity first identified as starlight scattered by interstellar dust by Sandage using the Galaxy Evolution Explorer (GALEX) ultraviolet imaging telescope. Apart from airglow and zodiacal emission, we have found a diffuse UV background of between 500 and 800 photons cm^–2 sr^–1 s^–1 Å^–1 in both the GALEX far-ultraviolet (FUV) (1350-1750 Å) and NUV (1750-2850 Å) bands. Of this emission, up to 250 photons cm^–2 sr^–1 s^–1 Å^–1 is due to H₂ fluorescent emission in the FUV band. The remainder is consistent with scattering from interstellar dust with forward scattering grains of albedo about 0.4. These are the highest spatial resolution observations of the diffuse UV background to date and show an intrinsic scatter beyond that expected from instrumental noise alone. Further modeling is required to understand the nature of this scatter and its implications for the ISM.

Key words: dust, extinction; scattering; ultraviolet: ISM

Print publication: Issue 2 (2009 February 20)
Received 2008 July 1, accepted for publication 2008 October 29
Published 2009 February 24