Testing a generalized cubic Galileon gravity model with the Coma Cluster
  We obtain a constraint on the parameters of a generalized cubic Galileon
gravity model exhibiting the Vainshtein mechanism by using multi-wavelength
observations of the Coma Cluster. The generalized cubic Galileon model is
characterized by three parameters of the turning scale associated with the
Vainshtein mechanism, and the amplitude of modifying a gravitational potential
and a lensing potential. X-ray and Sunyaev-Zeldovich (SZ) observations of the
intra-cluster medium are sensitive to the gravitational potential, while the
weak-lensing (WL) measurement is specified by the lensing potential. A joint
fit of a complementary multi-wavelength dataset of X-ray, SZ and WL
measurements enables us to simultaneously constrain these three parameters of
the generalized cubic Galileon model for the first time. We also find a
degeneracy between the cluster mass parameters and the gravitational
modification parameters, which is influential in the limit of the weak
screening of the fifth force.
