The shape of dark matter haloes in the Aquarius simulations: Evolution and memory

• Published in: EPJ Web of conferences Vol. 19; pp. 1009 - 1010
• Main Authors: Vera-Ciro, C.A., Sales, L.V., Helmi, A.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.01.2012
• ISBN: 2759807185; 9782759807185
• ISSN: 2100-014X; 2100-014X
• DOI: 10.1051/epjconf/20121901009

We use the high resolution cosmological N-body simulations from the Aquarius project to investigate in detail the mechanisms that determine the shape of Milky Way-type dark matter haloes. We find that, when measured at the instantaneous virial radius, the shape of individual haloes changes with time, evolving from a typically prolate configuration at early stages to a more triaxial/oblate geometry at the present day. This evolution in halo shape correlates well with the distribution of the infalling material: prolate configurations arise when haloes are fed through narrow filaments, which characterizes the early epochs of halo assembly, whereas triaxial/oblate configurations result as the accretion turns more isotropic at later times. Interestingly, at redshift z = 0, clear imprints of the past history of each halo are recorded in their shapes at different radii, which also exhibit a variation from prolate in the inner regions to triaxial/oblate in the outskirts. Provided that the Aquarius haloes are fair representatives of Milky Way-like 1012M☉ objects, we conclude that the shape of such dark matter haloes is a complex, time-dependent property, with each radial shell retaining memory of the conditions at the time of collapse.