Cluster infall in the concordance ΛCDM model

PIVATO, MAXIMILIANO C.; PADILLA, NELSON D.; LAMBAS, DIEGO G.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2006 vol. 373 p. 1409 - 1415

0035-8711

We perform statistical analyses of the infall of dark matter on to clusters in numerical simulations within the concordance ΛCDM (cold dark matter) model. By studying the infall profile around clusters of different mass, we find a linear relation between the mass and maximum infall velocities which reach ∼900 km s-1 for the most massive groups. The maximum infall velocity and the group mass follow a suitable power-law fit of the form V infmax = (M/m0)γ. By comparing the measured infall velocity to the linear infall model with an exponential cut-off introduced by Croft et al., we find that the best agreement is obtained for a critical overdensity δ5c = 45. We study the dependence of the direction of infall with respect to the cluster centres, and find that in the case of massive groups, the maximum alignment occurs at scales r ∼ 6h-1 Mpc. We obtain a logarithmic power-law relation between the average infall angle and the group mass. We also study the dependence of the results on the local dark matter density, finding a remarkable difference in the dynamical behaviour of low- and high-density particles. © 2006 RAS.