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A New Force in the Dark Sector?

Glennys R. Farrar, Rachel A. Rosen

astro-pharXiv:astro-ph/0610298

Abstract

We study the kinematics of dark matter using the massive cluster of galaxies 1E0657-56. The velocity of the &#34;bullet&#34; subcluster has been measured by X-ray emission from the shock front, and the masses and separation of the main and sub-clusters have been measured by gravitational lensing. The velocity with gravity alone is calculated in a variety of models of the initial conditions, mass distribution and accretion history; it is much higher than expected, by at least 2.4 sigma. The probability of so large a subcluster velocity in cosmological simulations is <~ 10-7. A long range force with strength ~ 0.4 - 1.2 times that of gravity would provide the needed additional acceleration.

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