Dissecting Galaxy Formation: I. Comparison Between Pure Dark Matter and Baryonic Models

Understand

We compare assembly of DM halos with and without baryons, within the context of cosmological evolution in the LCDM WMAP3 Universe (baryons+DM, BDM model, and pure DM, PDM model).

• In representative PDM and BDM models we find that baryons contribute decisively to the evolution of the central region, leading to an isothermal DM cusp, and to a flat DM density core -- the result of heating by dynamical friction of the substructure during a quiescent evolution epoch.
• This process ablates the cold gas from an embedded disk, cutting the star formation rate by ~10, and heats up the spheroidal gas and stellar components, triggering their expansion.
• The substructure is more resilient in the presence of baryons.