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ΛCDM doesn't enter into the Bullet Cluster. What we have is the following accounting: We can measure the mass of the hot intracluster medium. This gas is millions of kelvins and thus glowing predictably in X-rays. By measuring X-ray emissions, we know how much gas there is. Call this $M_\mathrm{gas}$. We can measure the mass of stars in galaxies. This is ...

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The first paper I looked at (Paraficz et al. 2012) explains that the hot gas mass is determined from X-ray observations. The X-ray flux from an optically thin gas depends on the square of the gas density multiplied by its volume - if you can then estimate the volume you get the density and also the gas mass. Some details for the analysis of the Chandra X-ray ...

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MOND does extremely well for spiral galaxies ($10^{10}-10^{12} M_0)$ in calculating with the measured tangential velocity as a function of radius. MOND has one constant $a_0=2 \times 10^{-8}{{cm}\over{sec^2}}$ used for all galaxies and uses the measured baryonic inside the radius for which the velocity is being calculated. MOND yields the baryonic ...

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It offers strong evidence that the unaccounted for mass (assuming a missing mass type scenario) behaves more like the stars (i.e. like a collision-less gas) than it does like the accounted for gas and dust (which exhibit a degree of viscosity). On the other hand, if you're trying to develop a MOND like theory it leaves you trying to argue that the ...

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Yes, dark matter should be considered to be a fluid which fills the space unoccupied by particles of matter. 'Cosmologists at Penn Weigh Cosmic Filaments and Voids' upenn [dot] edu/pennnews/news/cosmologists-penn-weigh-cosmic-filaments-and-voids "Dark matter ... permeate[s] all the way to the center of the voids." 'No Empty Space in the Universe --Dark ...

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Considering dark matter as a perfect fluid is useful for understanding cosmological evolution via the Friedmann acceleration equation $$3\frac{\ddot{a}}{a}=\Lambda - 4\pi G(\rho + 3p).$$ (note that this is a general relativistic equation, so not strictly Newtonian). Cosmologists use the equation of state parameter $w$ to relate ...

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