The observed satellite galaxies of satellite dwarf galaxies are one hundred times brighter than LambdaCDM simulations suggest that they should be, according to a new preprint. The conclusion is tentative, because it is based upon only four observations from a sample of 117 satellite galaxies. But no satellite of satellite galaxies this bright at all show up in LambdaCDM simulations, so finding this in a little less than 4% of the satellite galaxies in the sample still has considerable statistical power to show a problem with the LambdaCDM model or the simulation used to determine what it predicts.
In a similar challenge to the simulation based predictions of the LambdaCDM model, a new preprint examining the correlations between supermassive central black hole size, the stellar mass of stars in a galaxy, and the redshift at which the galaxy is observed, suggests that the feedback effects included in recent hydrodynamic simulations of galaxy formation are much too strong.
This is important because strong feedback effects are one of the main tools used to tune dark matter particle simulations to reproduce simulation results that look like the real world.
But if the models are greatly overstating the extent of real world feedback effects in galaxies, then this gravely undermines the ability of the dark matter particle theories simulated to accurately describe astronomy observations.
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