Evolution in the Halo Masses of Isolated Galaxies betweenz∼ 1 andz∼ 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_B0.6+/-0.1 at z~1 to σ∝ L_B0.4+/-0.1 at z~0. The evolution in M_200/M_ from z~1 to z~0 displays a bimodality insofar as host galaxies with stellar mass below M_ ~10¹¹ M_Sun/h maintain a constant ratio (the intrinsic increase is constrained to a factor of 1.1+/-0.7) while host galaxies above M_ ~10¹¹ M_Sun/h experience a factor of 4+/-3 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 LCDM 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 redshift and host galaxy stellar mass dependence of M_200/M_ agrees qualitatively with the Millennium Run semi-analytic model of galaxy formation. (ABRIDGED)