Cluster density profiles as a test of modified gravity

We present a new test of gravitational interactions at the r(0.2--20) Mpc scale, around the virial radius of dark matter halos measured through cluster-galaxy lensing of maxBCG clusters from the Sloan Digital Sky Survey (SDSS). We employ predictions from self-consistent simulations of $f(R)$ gravity to find an upper bound on the background field amplitude of |fR0|<3.5×10^-3 at the 1D-marginalized 95% confidence level. As a model-independent assessment of the constraining power of cluster profiles measured through weak gravitational lensing, we also constrain the amplitude F₀ of a phenomenological modification based on the profile enhancement induced by $f(R)$ gravity when not including effects from the increased cluster abundance in $f(R)$. In both scenarios, dark-matter-only simulations of the concordance model corresponding to |fR0|=0 and F₀=0 are consistent with the lensing measurements, i.e., at the 68% and 95% confidence level, respectively.