Evolution in the Halo Masses of Isolated Galaxies between z ~ 1 and z ~ 0: From DEEP2 to SDSS

We measure the evolution in the virial mass-to-light ratio (M₂₀₀/L_B) and virial-to-stellar mass ratio (M₂₀₀/M_*) for isolated ~L* galaxies between z~1 and z~0 by combining data from the DEEP2 Galaxy Redshift Survey and the Sloan Digital Sky Survey. Utilizing the motions of satellite galaxies around isolated galaxies, we measure line-of-sight velocity dispersions and derive dark matter halo virial masses for these host galaxies. At both epochs the velocity dispersion of satellites correlates with host galaxy stellar mass, σ~M^0.4+/-0.1_*, while the relation between satellite velocity dispersion and host galaxy B-band luminosity may grow somewhat shallower from σ~L^0.6+/-0.1_B at z~1 to σ~L^0.4+/-0.1_B at z~0. The evolution in M₂₀₀/M_* from z~1 to z~0 displays a bimodality insofar as host galaxies with stellar mass below M_*~10¹¹ h^-1 M_solar maintain a constant ratio (the intrinsic increase is constrained to a factor of 1.1+/-0.5) while host galaxies above M_*~10¹¹ h^-1 M_solar experience a factor of 3.3+/-2.2 increase in their virial-to-stellar mass ratio. This result can be easily understood if galaxies below this stellar mass scale continue to form stars while star formation in galaxies above this scale is quenched and the dark matter halos of galaxies both above and below this scale grow in accordance with ΛCDM cosmological simulations. Host galaxies that are red in U-B color have larger satellite dispersions and hence reside on average in more massive halos than blue galaxies at both z~1 and z~0. The satellite population of host galaxies varies little between these epochs. The redshift and host galaxy stellar mass dependence of M₂₀₀/M_* agrees qualitatively with the Millennium Run semianalytic model of galaxy formation.