Sam Llaneta with Andreas Berlind (Vanderbilt)

Dissecting the Angular Momentum of Dark Matter Halos

We want to test the current theory that the dark matter of a halo imparts its angular momentum on infalling gas, dust, and stars that ultimately forms the disks of galaxies. Under this model, the spin of dark matter halos should correlate strongly with the disk size of galaxies that form within them. We will investigate the possibility of measuring the spin of dark matter halos in large cosmological simulations by measuring the orbits of their subhalos. To do this we will first examine the relationship between the direction and magnitude of the spin angular momenta and spin parameters of host halos and the orbital angular momenta of their subhalos. A correlation between these quantities in the simulation may indicate an empirical relationship between them that we can observe. We will use a large N-body dark matter only simulation to examine a large and thorough set of halos. The next step will be using the simulation to determine whether such a relationship is observable from the radial velocities of galaxies as viewed from a fixed point. The ultimate goal of this project is to measure the spin of the host halos of populations of galaxy groups from earth using the redshifts of galaxies within the groups. This will hopefully shed insight on the validity of our current understanding of disk formation in galaxies.