Star Formation and Threshold in Nearby Galaxies Observed with GALEX

Star formation on galactic scales is the process driving the evolution of galaxies. It is important to understand its various aspects in the nearby universe to properly interpret high redshift observations, and to construct correct models of the evolution of galaxies. Combining UV (GALEX) and infrared (IRAS) data for 43 nearby spatially resolved galaxies with corollary data (HI,CO), we study the star formation law ("Schmidt" law). The absence of a "threshold radius" in the UV supports the idea that star formation proceed at low gas densities and that the usual threshold observed in H-alpha profiles is a small-number statistic effect.