OBSERVATIONS OF THE GALACTIC AND EXTRAGALACTIC BACKGROUND WITH THE FAR-ULTRAVIOLET SPACE TELESCOPE (FAUST)

We present new results from a search for an extragalactic background c omponent in far-ultraviolet (FUV) diffuse emission. We have obtained t hree FUV ultraviolet scanned images covering several tens of square de grees using a space-borne imaging telescope (FAUST). We have also util ized 12 other FAUST pointed images taken at a range of Galactic latitu des for other purposes. Previous attempts at detecting the extragalact ic background have utilized the power spectrum of images to separate t he Galactic and extragalactic signals. To search for an extragalactic signature, we calculate and present the spatial power spectrum and aut ocorrelation function of the diffuse light in the FAUST images. We cal culate also the power spectrum of 100 mu m images from the Infrared As tronomical Satellite (IRAS) of the same fields. The spectra from both instruments show a consistent power law with similar spectral index an d amplitude ratio. We examine a variety of possible explanations for t he signal observed but finally attribute the signal at FUV wavelengths to starlight scattered from dust. We argue that this indicates that o ur search and earlier searches for the fluctations due to extragalacti c light at FUV and optical wavelengths have detected only this Galacti c source, and we discuss the implications of this conclusion on the st ar formation in galaxies. We make an estimate of the sensitivity neede d to separate a possible extragalactic signal from the Galactic foregr ound we measure. We conclude that searching for an extragalactic power law signal is not a viable search technique given the brightness and fluctuations of the Galactic foreground signal. We infer that the actu al limits on the star formation are less than dM/dt < 0.033 M. yr(-1) Mpc(-3) h(-2) and that the FUV luminosity of galaxies at z = 0.6 is le ss than 1.6 times the current luminosity.