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Abstract: Collisionless simulations of the CDM cosmology predict a plethora of darkmatter substructures in the halos of Milky Way sized galaxies, yet the numberof known luminous satellites galaxies is very much smaller, a discrepancy thathas become known as the `missing satellite problem-. The most massivesubstructures have been shown to be plausibly the hosts of the brightestsatellites, but it remains unclear which processes prevent star formation inthe many other, purely dark substructures. We use high-resolution hydrodynamicsimulations of the formation of Milky Way sized galaxies in order to test howwell such self-consistent models of structure formation match the observedproperties of the Galaxy-s satellite population. For the first time, we includein such calculations feedback from cosmic rays injected into the star forminggas by supernovae as well as the energy input from supermassive black holesgrowing at the Milky Way-s centre and its progenitor systems. We find thatnon-thermal particle populations quite strongly suppress the star formationefficiency of the smallest galaxies. In fact, our cosmic ray model is able toreproduce the observed faint-end of the satellite luminosity function, whilemodels that include only the effects of cosmic reionization, or galactic winds,do significantly worse. Our simulated satellite population approximatelymatches available kinematic data on the satellites and their observed spatialdistribution. We conclude that a proper resolution of the missing satelliteproblem likely requires the inclusion of non-standard physics for regulatingstar formation in the smallest halos, and that cosmic reionization alone maynot be sufficient.



Author: M. Wadepuhl, V. Springel

Source: https://arxiv.org/



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