The angular momentum of cold dark matter haloes with and without baryons

Understand

We investigate the magnitude and internal alignment of the angular momentum of cold dark matter haloes in simulations with and without baryons.

• We analyse the cumulative angular momentum profiles of hundreds of thousands of haloes in the Millennium simulation and in a smaller, but higher resolution, simulation, in total spanning 5 orders of magnitude in mass.
• For haloes of a given mass, the median specific angular momentum increases as j(<r) proportional to r.
• The direction of the vector varies considerably with radius: the median angle between the inner (< 0.25 Rvir) and total (< Rvir) angular momentum vectors is about 25degr.