We model the evolution of the mean galaxy occupation of dark-matter halos over the range 0.1 < z < 1.3 , using the data from the VIMOS-VLT Deep Survey ( VVDS ) .
The galaxy projected correlation function w _ { p } ( r _ { p } ) was computed for a set of luminosity-limited subsamples and fits to its shape were obtained using two variants of Halo Occupation Distribution models .
These provide us with a set of best-fitting parameters , from which we obtain the average mass of a halo and average number of galaxies per halo .
We find that after accounting for the evolution in luminosity and assuming that we are largely following the same population , the underlying dark matter halo shows a growth in mass with decreasing redshift as expected in a hierarchical structure formation scenario .
Using two different HOD models , we see that the halo mass grows by 90 % over the redshift interval z= [ 0.5,1.0 ] .
This is the first time the evolution in halo mass at high redshifts has been obtained from a single data survey and it follows the simple form seen in N-body simulations with M ( z ) = M _ { 0 } e ^ { - \beta z } , and \beta = 1.3 \pm 0.30 .
This provides evidence for a rapid accretion phase of massive halos having a present-day mass M _ { 0 } \sim 10 ^ { 13.5 } h ^ { -1 } M _ { \odot } , with a m > 0.1 M _ { 0 } merger event occuring between redshifts of 0.5 and 1.0 .
Futhermore , we find that more luminous galaxies are found to occupy more massive halos irrespectively of the redshift .
Finally , the average number of galaxies per halo shows little increase from redshift z \sim 1.0 to z \sim 0.5 , with a sharp increase by a factor \sim 3 from z \sim 0.5 to z \sim 0.1 , likely due to the dynamical friction of subhalos within their host halos .