CFHTLenS: co-evolution of galaxies and their dark matter haloes

Galaxy-galaxy weak lensing is a direct probe of the mean matter distribution around galaxies. The depth and sky coverage of the Canada-France-Hawaii Telescope Legacy Survey yield statistically significant galaxy halo mass measurements over a much wider range of stellar masses (10(8.75) to 10(11.3) M-circle dot) and redshifts (0.2 <z <0.8) than previous weak lensing studies. At redshift z similar to 0.5, the stellar-to-halo mass ratio (SHMR) reaches a maximum of 4.0 +/- 0.2 per cent as a function of halo mass at similar to 10(12.25) M-circle dot. We find, for the first time from weak lensing alone, evidence for significant evolution in the SHMR: the peak ratio falls as a function of cosmic time from 4.5 +/- 0.3 per cent at z similar to 0.7 to 3.4 +/- 0.2 per cent at z similar to 0.3, and shifts to lower stellar mass haloes. These evolutionary trends are dominated by red galaxies, and are consistent with a model in which the stellar mass above which star formation is quenched 'downsizes' with cosmic time. In contrast, the SHMR of blue, star-forming galaxies is well fitted by a power law that does not evolve with time. This suggests that blue galaxies form stars at a rate that is balanced with their dark matter accretion in such a way that they evolve along the SHMR locus. The redshift dependence of the SHMR can be used to constrain the evolution of the galaxy population over cosmic time.