NIHAO IX: the role of gas inflows and outflows in driving the contraction and expansion of cold dark matter haloes

Understand

We use ~100 cosmological galaxy formation zoom-in simulations using the smoothed particle hydrodynamics code {\sc gasoline} to study the effect of baryonic processes on the mass profiles of cold dark matter haloes.

• The haloes in our study range from dwarf (M_{200}~10^{10}Msun) to Milky Way (M_{200}~10^{12}Msun) masses.
• Our simulations exhibit a wide range of halo responses, primarily varying with mass, from expansion to contraction, with up to factor ~10 changes in the enclosed dark matter mass at one per cent of the virial radius.
• Confirming previous studies, the halo response is correlated with the integrated efficiency of star formation: e_SF=(M_{star}/M_{200})/(\Omega_b/\Omega_m).