L(Hα) versus diameter relation. Blue points are Sknot galaxies. Circled enclosed points were discarded for the fit because of contamination in the flux (see Sect. 6.2). Green points are Sknot, with L(Hα) determined photometrically and spectroscopically; the error bar is the difference in luminosities. The mean value of the errors is taken as proxy error for the measurements (error bar for blue points). Red points are estimations of L(Hα) of clumps with a Monte Carlo simulation. The solid red line is the best fit for red points and solid blue line is the best fit for Sknot galaxies.