Zoomed cosmological simulations of Milky Way-sized haloes in f(R) gravity

Abstract

We investigate the impact of f(R) modified gravity on the internal properties of Milky Waysized dark matter haloes in a set of cosmological zoom simulations of seven haloes from the Aquarius suite, carried out with our code MG-GADGET in the Hu & Sawicki f(R) model. Also, we calculate the fifth forces in ideal NFW-haloes as well as in our cosmological simulations and compare them against analytic model predictions for the fifth force inside spherical objects. We find that these theoretical predictions match the forces in the ideal haloes very well, whereas their applicability is somewhat limited for realistic cosmological haloes. Our simulations show that f(R) gravity significantly affects the darkmatter density profile of MilkyWay-sized objects as well as their circular velocities. In unscreened regions, the velocity dispersions are increased by up to 40 per cent with respect to ΛCDM for viable f(R) models. This difference is larger than reported in previous works. The Solar circle is fully screened in fR0 = -10-6 models for MilkyWay-sized haloes, while this location is unscreened for slightly less massive objects. Within the scope of our limited halo sample size, we do not find a clear dependence of the concentration parameter of dark matter haloes on fR0.