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 component in far-ultraviolet (FUV) diffuse emission. We have obtained three FUV ultraviolet scanned images covering several tens of square degrees using a space-borne imaging telescope (FAUST). We have also utilized 12 other FAUST pointed images taken at a range of Galactic latitudes for other purposes. Previous attempts at detecting the extragalactic background have utilized the power spectrum of images to separate the Galactic and extragalactic signals. To search for an extragalactic signature, we calculate and present the spatial power spectrum and autocorrelation function of the diffuse light in the FAUST images. We calculate also the power spectrum of 100 mu m images from the Infrared Astronomical Satellite (IRAS) of the same fields. The spectra from both instruments show a consistent power law with similar spectral index and amplitude ratio. We examine a variety of possible explanations for the signal observed but finally attribute the signal at FUV wavelengths to starlight scattered from dust. We argue that this indicates that our search and earlier searches for the fluctations due to extragalactic light at FUV and optical wavelengths have detected only this Galactic source, and we discuss the implications of this conclusion on the star formation in galaxies. We make an estimate of the sensitivity needed to separate a possible extragalactic signal from the Galactic foreground 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 actual 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 less than 1.6 times the current luminosity.