Exploring the liminality: properties of haloes and subhaloes in borderline $f(R)$ gravity

Understand

We investigate the properties of dark matter haloes and subhaloes in an $f(R)$ gravity model with $|f_{R0}|=10^{-6}$, using a very high-resolution N-body simulation.

• The model is a borderline between being cosmologically interesting and yet still consistent with current data.
• We find that the halo mass function in this model has a maximum 20% enhancement compared with the $\Lambda$CDM predictions between $z=1$ and $z=0$.
• Because of the chameleon mechanism which screens the deviation from standard gravity in dense environments, haloes more massive than $10^{13}h^{-1}M_\odot$ in this $f(R)$ model have very similar properties to haloes of similar mass in $\Lambda$CDM, while less massive haloes, such as that of the Milky Way, can have steeper inner density profiles and higher velocity dispersions due to their weaker screening.