1610.07592
The segregation of baryons and dark matter during halo assembly
Liao, et al
The standard galaxy formation theory assumes that baryons and DM are initially well-mixed before becoming segregated due to radiative cooling. Use non-radiative hydro-sims to explicitly examine this assumption and find that baryons and DM can also be segregated during the build-up of the halo. As a result, baryons in many haloes do not originate from the same Lagrangian region as the DM. When using the fraction of corresponding DM and gas particles in the initial conditions (the "paired fraction") as a proxy of the DM and gas segregation strength of a halo, on average about 25% of the baryonic and DM of the final halo are segregated in the initial conditions. A consequence of this effect is that the baryons and DM of the same halo initially experience different tidal torques and thus their angular momentum vectors are often misaligned. This is at odds with the assumption of the standard galaxy formation model, and challenges the precision of some semi-analytical approaches which utilize DM halo merger trees to infer properties of gas associated to DM haloes.
No comments:
Post a Comment