Large scale anisotropies in peculiar velocity fields

LAURA CECCARELLI; DANTE J. PAZ; NELSON PADILLA; DIEGO G. LAMBAS

Salta, Argentina

Conferencia; 53a. Reunión Anual de la Asociación Argentina de Astronomía; 2010

Instituto de Astronomía Teórica y Experimental

We perform a statistical analysis of the peculiar velocity field around dark matter haloes in numerical simulations. We examine different properties of the infall of material onto haloes and its relation to central halo shapes and surrounding large scale structures.We find that the amplitude of the infall velocity field along the halo shape minor axis is larger than that along the major axis. This is consistent for general triaxial haloes, and for both prolate and oblate systems.We also report a strong anisotropy of the velocity field along the principal axes of the surrounding large scale structure. The infall velocity field around dark matter haloes reaches a maximum value along the direction of underdense, large-scale surrounding regions (LSS minor axis), meanwhile along the direction of dense, large-scale regions, it exhibits the smallest velocities.We also analyse the dependence of the matter velocity field on the local environment. The amplitude of the infall velocity at high local density regions is larger than at low local density regions.We examine the laminarity of the flow through the ratio between flow velocity and velocity dispersion. The velocity field tends to be more laminar along the direction towards underdense surrounding regions. We also detect an anisotropic mass outflow from the groups. Regarding the principal axes of the surrounding structure we find that the largest outflow velocity amplitude occurs along theLSS major axis direction.