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 _ { \hbox { $ \odot$ } } ) and redshifts ( 0.2 < z < 0.8 ) than previous weak lensing studies .
At redshift 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 _ { \hbox { $ \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 .