Oral Presentation
Solving the cooling flow problem by introducing non gravitational dark matter-baryon interaction
Presenter: Hiroki Ichihashi (Hokkaido University)
Clusters of galaxies are the largest self-gravitating objects in the universe. The gas content of the clusters is mostly in diffuse, hot plasma phase. Naively, there must be the cold gas in the central part of the clusters since the cooling time there is shorter than the age of the universe. Observations have, however, not found the cold gas and this apparent contradiction is known as the cooling flow problem. We here introduce weakly charged dark matter that has non-zero but much smaller charge than an electron. This dark matter is hence allowed to interact with baryons electro-magnetically. Specifically, the relative velocity between dark matter and gas decreases due to inelastic scattering of protons by the dark matter particles. The reduced kinetic energy is used to increase the internal energy of the gas. Our simulations show that the dark matter-baryon interaction can offset the cooling in the cluster cores and solve the cooling flow problem if the interaction cross-section is sufficiently large.
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