2015MNRAS.447..298H

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 (108.75 to 10^11.3M_☉) and redshifts (0.2 < z < 0.8) than previous weak lensing studies. At redshift z ∼ 0.5, the stellar-to-halo mass ratio (SHMR) reaches a maximum of 4.0±0.2 percent as a function of halo mass at ∼ 10^12.25M_☉. 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 percent at z ∼ 0.7 to 3.4±0.2 percent at z ∼ 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.