The Halo Shape-Dynamics-Age Relation in the MareNostrum Universe

RAGONE-FIGUEROA C.; PLIONIS M.; GOTTLOEBER S.; YEPES G.

Isla de Margarita, Venezuela

Congreso; 12th Latin-American Regional IAU Meeting (LARIM-2007); 2007

We use dark matter haloes identified in the MareNostrum Universe (500 h-1 Mpc box with 10243 DM and 10243 gas particles; Gottloeber & Yepes 2007) to study the relation between halo shape and halo dynamics, within small halo mass ranges. A strong correlation is present which we find it to be due to the halo formation time. Early formation time haloes are more spherical and have higher velocity dispersions than late forming haloes. For the late formation time haloes we find a further effect which is correlated to the halo substructure; as the halo substructure decreases the velocity dispersion increases. On the contrary, among the early formation time haloes, which can be considered as virialized haloes, there is no obvious distinction between those that have more or less substructure. These effects indicate that using the virial relation to estimate group or cluster of galaxies dynamical mass, without taking them into account, has important caveats.