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A New Force in the Dark Sector?

Glennys R. Farrar·Rachel A. Rosen
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Abstract

We study the kinematics of dark matter using the massive cluster of galaxies 1E0657-56. The velocity of the "bullet" 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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Glennys R. Farrar, Rachel A. Rosen. 2007-03-15. A New Force in the Dark Sector?. https://doi.org/10.1103/physrevlett.98.171302

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