ULTRAVIOLET OBSERVATIONS OF GALAXIES WITH THE FAUST EXPERIMENT

We have used the set of point sources detected by the FAUST instrument to identify galaxies and study the total galaxy flux in a 250 Angstro m wide band peaking at 1650 Angstrom. A sample of 144 galaxies has bee n obtained after cross-reference with the RC3 catalog, elimination of objects confused with stars and various corrections for the photometry . The UV-B color dispersion is found to increase while the galaxies ge t redder from late to early types. The irregular galaxies appear on av erage redder and the Sbc galaxies bluer than indicated by the spectral energy distributions currently used for the calculations of K-correct ions. Various arguments lead us to make the assumption of a constant d ust extinction within each galaxy. The UV flux per unit area decreases on average from late to early type spirals. We find a weak correlatio n between the UV and far infra-red emission while the infra-red to UV flux ratio gets lower when galaxies get bluer (as measured by the UV t o B flux ratio). The UV flux per unit area correlates with the HI gas surface density and the total gas surface density when this quantity i s available. The correlation with the molecular gas alone is weak. In the Virgo cluster, the UV flux per unit area does not decrease in dire ct proportion to the HI deficiency. Galaxy counts per square degree an d per magnitude interval have been obtained at high-galactic latitudes . Combined with data at fainter magnitudes, they show a variation as a function of magnitude with a near-euclidean slope over a range of 8 m agnitudes.