Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-09-30
Astrophys.J. 747 (2012) 45
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Accepted for publication in ApJ, correlations between the mean infall pairwise velocities of the bullet-like systems and the e
Scientific paper
It has been recently shown that the observed morphological properties of the Bullet Cluster can be accurately reproduced in hydrodynamical simulations only when the infall pairwise velocity V_{c} of the system exceeds 3000km/s (or at least possibly 2500 km/s) at the pair separation of 2R_{vir}, where R_{vir} is the virial radius of the main cluster, and that the probability of finding such a bullet-like system is extremely low in the standard \Lambda CDM cosmology. We suggest here the fifth-force mediated by a coupled Dark Energy (cDE) as a possible velocity-enhancing mechanism and investigate its effect on the infall velocities of the bullet-like systems from the CoDECS (COupled Dark Energy Cosmological Simulations) public database. Five different cDE models are considered: three with constant coupling and exponential potential, one with exponential coupling and exponential potential, and one with constant coupling and supergravity potential. For each model, after identifying the bullet-like systems, we determine the probability density distribution of their infall velocities at the pair separations of (2-3)R_{vir}. Approximating each probability density distribution as a Gaussian, we calculate the cumulative probability of finding a bullet-like system with V_{c}>=3000 km/s or V_{c}>=2500 km/s. Our results show that in all of the five cDE models the cumulative probabilities increase compared to the \Lambda CDM case and that in the model with exponential coupling P(V_{c}>=2500 km/s) exceeds 10^{-4}. The physical interpretations and cosmological implications of our results are provided.
Baldi Marco
Lee Jounghun
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