MAPPING THE DIFFUSE ULTRAVIOLET SKY WITH THE GALAXY EVOLUTION EXPLORER

We present a map of the diffuse ultraviolet cosmic background in two wavelength bands (FUV: 1530 angstrom and NUV: 2310 angstrom) over almost 75% of the sky using archival data from the Galaxy Evolution Explorer (GALEX) mission. Most of the diffuse flux is due to dust-scattered starlight and follows a cosecant law with slopes of 545 photons cm(-2) s(-1) sr(-1) angstrom(-1) and 433 photons cm(-2) s(-1) sr(-1) angstrom(-1) in the FUV and NUV bands, respectively. There is a strong correlation with the 100 mu m Infrared Astronomy Satellite (IRAS) flux with an average UV/IR ratio of 300 photons cm(-2) s(-1) sr(-1) angstrom(-1) (MJy sr(-1))(-1) in the FUV band and that of 220 photons cm(-2) s(-1) sr(-1) angstrom(-1) (MJy sr(-1))(-1) in the NUV band but with significant variations over the sky. In addition to the large-scale distribution of the diffuse light, we note a number of individual features including bright spots around the hot stars Spica and Achernar.