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tokens: bars stand for standard deviations of the mean correlation functions. As expected, dark matter particles within the closely bound regions of the haloes do not present any particular arrangement (red dashed line), they are homogeneously distributed around the centre of masses. When considering all the particles within a 6 h −1 Mpc radius sphere, the layout is not that much different, although the trend of a preferential direction begins to appear more clearly (black dotted line). Finally, selecting only infalling particles outside the closely bound regions but within 6 h −1 Mpc the signal (blue solid line) is quite strong: there are 5 ± 2 times more particles forming a small angle between themselves than when considering a random distribution and the particles, i.e. infalling particles are non uniformly distributed around the haloes. Knowing that particles falling on to the inner part of dark matter haloes are arranged along a preferred direction, the mean positions of the infalling particles in the different simulations can be derived. We find that the mean coordinates obtained for the different simulations are very similar in all the realizations. The resulting direction of ‘close’ (in the sense that only particles within 6 h −1 Mpc are considered) infall is, on average, along the axis formed between the mean position of Virgo haloes (−4.5 ± 0.6; 8.3 ± 0.4; 0.99 ± 0.8) h −1 Mpc in supergalactic coordinates and the point of supergalactic Cartesian coordinates (−4.8 ± 0.6; 9.3 ± 0.5; 0.26 ± 0.8) h −1 Mpc. To compare with the observed infall, it seems reasonable to look at farther particles. The resulting ‘far’ infall is illustrated by Aitoff projections in Fig. 6 where particles (yellow dots) are shown to fall along the filament linked to the observed Virgo cluster (thick red cross)/ simulated Virgo halo (orange cross). The particles come on average from the supergalactic Cartesian coordinates (−1.5,7.5,−0.05) h −1 Mpc, the supergalactic longitude and latitude (101.45,−0.337) in degrees and the galactic longitude and latitude (287.57,76.77) in degrees. The top projection is centred on the observer (blue cross) while the bottom projection is centred on the observed Virgo cluster. This is in agreement with West Blakeslee ( 2000 ) who suggest that infall of material along the Virgo-Abell 1367 filament has driven the formation of the Virgo cluster. The observational latitude and longitude coordinates, (235.08,73.02) in degrees, of the Abell 1367 cluster (violet triangle) are indeed very close to the direction of infall in the simulations. Figure 6. Aitoff projection in supergalactic (top) and galactic (bottom) coordinates of galaxies from the V8k redshift catalogue (black dots), of the observer (thick blue cross), of the observed Virgo cluster (thick red cross), of one Virgo halo (orange cross) and of the particles infalling on to this halo at redshift zero (yellow dots) The size of the dots in this latter case is proportional to the infall