Internal kinematics of blue Canada-France Redshift Survey galaxies at z similar to 0.6

We present the results of a study of the internal kinematics of luminous st ar-forming galaxies in the 0 < z < 0.8 range, with the aim of investigating the nature of the blue galaxies that cause the largest changes in the lumi nosity function at z greater than or equal to 0.5. New kinematic data are a nalyzed for a sample of 24 galaxies from the Canada-France Redshift Survey (CFRS), most of them with rest-frame (U-V)(AB) less than or equal to 1.14. Unlike most previous studies, target galaxies were selected regardless of s ize and morphology, from a well-studied magnitude-limited survey (the CFRS) . Our sample is therefore representative of the most rapidly changing one-t hird of the galaxy population in the 0 < z < 0.8 range. The 15 galaxies at z > 0.45 have sizes (from Hubble Space Telescope images) and velocity width s a, (from emission lines) similar to those of typical local irregular gala xies. This is consistent with their morphologies and rest-frame colors; how ever, these galaxies are as bright as the brightest local irregular galaxie s and roughly 2 mag brighter than the typical irregular galaxies known near by. We conclude that the increase in the number density of luminous blue ga laxies at z greater than or equal to 0.5 is mainly due to a population of s mall and unusually bright late-type galaxies.