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 CFHT Legacy Survey yield statistically significant galaxy halo mass measurements over a much wider range of stellar masses (${10}^{8.75}$ to ${10}^{11.3}{M}_{\odot }$) and redshifts ($0.2 < z < 0.8$)thanpreviousweaklensingstudies\mathrm{.}Atredshift$z \sim 0.5$, the stellar-to-halo mass ratio (SHMR) reaches a maximum of $4.0\pm 0.2$ percent as a function of halo mass at $\sim {10}^{12.25}{M}_{\odot }$. 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 $4.5\pm 0.3$ percent at $z\sim 0.7$ to $3.4\pm 0.2$ percent at $z\sim 0.3$, 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-fit 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.