The angular momentum distribution within haloes in different dark matter models

We study the angular momentum profile of dark matter haloes for a statistical sample drawn from a set of high-resolution cosmological simulations of 256(3) particles. Two typical cold dark matter (CDM) models have been analysed, and the haloes are selected to have at least 3 x 10(4) particles in order to measure the angular momentumprofile reliably. In contrast with the recent claims of Bullock et al., we find that the degree of misalignment of angular momentum within a halo is very high. Approximately 50 per cent of haloes have more than 10 per cent of the halo mass in the mass of negative angular momentum j. After the mass of negative j is excluded, the cumulative mass function M(<j) follows approximately the universal function proposed by Bullock et al., although we still find a significant fraction of haloes (similar to 50 per cent) that exhibit systematic deviations from the universal function. Our results, however, are broadly in good agreement with a recent work of van den Bosch et al. We also study the angular momentum profile of haloes in a warm dark matter (WDM) model and a self-interacting dark matter (SIDM) model. We find that the angular momentum profile of haloes in the WDM is statistically indistinguishable from that in the CDM model, but the angular momentum of haloes in the SIDM is reduced by the self-interaction of dark matter.