Can Coupled Dark Energy Speed Up the Bullet Cluster?

It has been recently shown that the observed properties of Bullet Cluster can be accurately reproduced in hydrodynamical only when the infall pairwise velocity Vc of the exceeds 3000 km s-1 (or at least possibly 2500 km -1) at the pair separation of 2R vir, where R is the virial radius of the main cluster, and that the of finding such a bullet-like system is extremely low in the Λ cold dark matter (ΛCDM) cosmology. We suggest the fifth force mediated by coupled dark energy (cDE) as a possible -enhancing mechanism and investigate its effect on the infall of bullet-like systems from the Coupled Dark Energy Simulations public database. Five different cDE models are: three with constant coupling and exponential potential, one exponential coupling and exponential potential, and one with coupling and supergravity potential. For each model, after the bullet-like systems, we determine the probability distribution of their infall velocities at pair separations of (2-3) R vir. Approximating each probability density as a Gaussian, we calculate the cumulative probability of a bullet-like system with Vc >= 3000 km -1 or Vc >= 2500 km s-1. Our show that in all of the five cDE models the cumulative increase compared to the ΛCDM case and that in the with exponential coupling P (Vc >= 2500 km -1) exceeds 10-4. The physical interpretations cosmological implications of our results are provided.