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

TL;DR

This study uses zoom simulations to explore how f(R) modified gravity influences the internal structure of Milky Way-sized dark matter halos, revealing significant effects on density profiles and velocities, with implications for gravity theories.

Contribution

First detailed cosmological zoom simulations of Milky Way-sized halos in f(R) gravity, comparing theoretical fifth force predictions with realistic halo properties.

Findings

f(R) gravity alters dark matter density profiles and circular velocities.

Velocity dispersions can increase by up to 40% in unscreened regions.

Solar circle is screened in certain f(R) models for Milky Way-sized halos.

Abstract

We investigate the impact of f(R) modified gravity on the internal properties of Milky Way sized dark matter halos in a set of cosmological zoom simulations of seven halos 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-halos 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 halos very well, whereas their applicability is somewhat limited for realistic cosmological halos. Our simulations show that f(R) gravity significantly affects the dark matter density profile of Milky Way sized objects as well as their circular velocities. In unscreened regions, the velocity dispersions are increased by up to 40% with respect to LCDM for viable f(R) models. This difference is larger than reported in previous works. The Solar circle is fully screened in $f_{R0} = -10^{-6}$ models for Milky Way sized halos, 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 halos on $f_{R0}$.