Shape of Dark Matter Haloes in the Illustris Simulation: Effects of Baryons

Understand

We study the effect of baryonic processes on the shapes of dark matter (DM) haloes from Illustris, a suite of hydrodynamical (Illustris) and DM-only (Illustris-Dark) cosmological simulations performed with the moving-mesh code {\sc arepo}.

• DM halo shapes are determined using an iterative method based on the inertia tensor for a wide range of $z=0$ masses ($M_{200} = 1 \times 10^{11} - 3 \times 10^{14} M_\odot$).
• Convergence tests shows that the local DM shape profiles are converged only for $r > 9\epsilon$, $\epsilon$ being the Plummer-equivalent softening length, larger than expected.
• Haloes from non-radiative simulations (i.e.