Tobias Goerdt, Andreas Burkert
Recent observations have shown that the majority of the Andromeda galaxy's satellites are aligned in a thin plane. On the theoretical side it has been proposed that galaxies acquire their gas via cold streams. In addition, numerical simulations show that the same streams also deliver satellites. Assuming that cold streams are the major source of satellite systems around galaxies we calculate the probabilities to find a certain fraction of satellites within a thin plane around the central galaxy of the host halo. Using simple geometrical considerations and adopting a random orientation of the streams we demonstrate that the vast thin disk of satellites detected around Andromeda can naturally be explained within this framework. In fact, without any satellite scattering, three streams or less would lead to too many satellites in the thin plane, compared with the observations. Four to seven streams reproduce the observations very well. Thin disks of satellites might therefore provide important relic information about the early phases of gas accretion of galaxies and can be interpreted as indirect observational evidence for the cold stream paradigm.
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http://arxiv.org/abs/1307.2102
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