Modelling galaxy stellar mass evolution fromz ∼ 0.8to today

We apply the empirical method built for redshift z= 0 in the previous work of Wang et al. to a higher redshift, to link galaxy stellar mass directly with its hosting dark matter halo mass at a redshift of around 0.8. The Mstars–Minfall relation of the galaxy stellar mass Mstars and the host halo mass Minfall is constrained by fitting both the stellar mass function and the correlation functions at different stellar mass intervals of Visible Multiobject Spectrograph–Very Large Telescope Deep Survey (VVDS) observations, where Minfall is the mass of the hosting halo at the time when the galaxy was last the central galaxy. We find that for low-mass haloes, the residing central galaxies at high redshift are less massive than those at low redshift. For high-mass haloes, central galaxies in these haloes at high redshift are somewhat more massive than the galaxies at low redshift. Satellite galaxies are less massive at earlier times, for any given mass of hosting halo. Fitting both Sloan Digital Sky Survey (SDSS) and VVDS observations simultaneously, we also propose a unified model of the Mstars–Minfall relation, which describes the evolution of central galaxy mass as a function of time. The stellar mass of a satellite galaxy is determined by the Mstars–Minfall relation of central galaxies at the time when the galaxy is accreted and becomes a subcomponent of a larger group. With these models, we study the amount of galaxy stellar mass increase from z∼ 0.8 to the present day through galaxy mergers and star formation. Low-mass galaxies (h−1 M) gain their stellar masses from z∼ 0.8 to z= 0 mainly through star formation. For galaxies of higher mass, we find that the increase of stellar mass solely through mergers from z= 0.8 can make massive galaxies a factor ∼2 larger than observed at z= 0, unless the satellite stellar mass is scattered to intracluster stars by gravitational tidal stripping or to the extended halo around the central galaxy, which is not counted in local observations. We can also predict stellar mass functions for redshifts up to z∼ 3, and the results are consistent with the latest observations. In future, more precise observational data will allow us better to constrain our model.