Far infrared and Ultraviolet emissions of individual galaxies at z=0: selection effects on the estimate of the dust extinction

We have cross-correlated Far Infrared (IRAS) and UV (FOCA) observations of galaxies to construct a sample of FIR selected galaxies with a UV observati on at 0.2 mu m. The FIR and UV properties of this sample are compared to the mean propertie s of the local Universe deduced from the luminosity distributions at both w avelengths. Almost all the galaxies of our sample have a FIR to UV Aux rati o larger than the ratio of the FIR and UV luminosity densities, this effect becoming worse as the galaxies become brighter: the increase of the UV (0. 2 mu m) extinction is about 0.5 mag per decade of FIR (60 mu m) luminosity. Quantitative star formation rates are estimated by adding the contribution of the FIR and UV emissions. They are found consistent with the corrections for extinction deduced from the FIR to UV flux ratio. A total local volume -average star formation rate is calculated by summing the contribution of t he FIR and UV wavelengths bands. Each band contributes for an almost simila r amount to the total star formation rate with rho(SFR) = 0.03 +/- 0.01 h.M . /yr/Mpc(3) at z=0. This is equivalent to a global extinction of 0.75 mag to apply to the local luminosity density at 0.2 mu m. The trend of a larger FIR to UV flux ratio for a larger FIR luminosity foun d for our sample of nearby galaxies is extended and amplified toward the ve ry large FIR luminosities when we consider the galaxies detected by ISOCAM in a CFRS field and the Ultra Luminous Infrared Galaxies at low and high re dshift. A UV extinction is tentatively estimated for these objects.