  In this work we focus on the properties of accretion onto galaxies. Through
numerical simulations we investigate the geometrical properties of accretion.
To span the scale range required in these simulations we have developed a new
numerical technique: the multi-zoom method. We run a series of Tree-SPH
simulations in smaller and smaller boxes at higher and higher mass resolution,
using data recorded at the previous level to account for the matter inflow and
the tidal field from outside matter. The code is parallelized using OpenMP. We
present a validation test to evaluate the robustness of the method: the pancake
collapse. We apply this new multizoom method to study the accretion properties.
Zooming in onto galaxies from a cosmological simulation, we select a sample of
10 well resolved galaxies (5000 baryonic particles or more). We sum up their
basic properties and plot a Tully-Fisher relation. We find that smooth
accretion of intergalactic cold gas dominates mergers for the mass growth of
galaxies at z < 2. Next we study the baryonic accretion rate which shows
different behaviours depending on the galaxy mass. The bias is also computed at
different radii and epochs. Then we present galactocentric angular maps for the
accretion integrated between z=2 and z=0, which reveal that accretion is highly
anisotropic. Average accretion rates plotted against galactocentric latitude
show a variety of behaviours. In general, accretion in the galactic plane is
favored, even more for baryonic matter than for dark matter.
