The shape of the invisible halo: N‐body simulations on parallel supercomputers

We study the shapes of halos and the relationship to their angular momentum content by means of N‐body (N∼106) simulations. Results indicate that in relaxed halos with no apparent substructure: i.) The shape and orientation of the isodensity contours tends to persist throughout the virialized portion of the halo. ii.) Most (≊70%) of the halos are prolate. iii.) The approximate direction of the angular momentum vector tends to persist throughout the halo. iv.) For spherical shells centered on the core of the halo the magnitude of the specific angular momentum is approximately proportional to their radius. v.) The shortest axis of the ellipsoid which approximates the shape of the halo tends to align with the rotation axis of the halo. This tendency is strongest in the fastest rotating halos.