http://arxiv.org/abs/1401.6459
The emptiness of the Local Void has been put forward as a serious challenge to the current standard paradigm of structure formation in $\Lambda$CDM. We use a high resolution cosmological N-body simulation, the Millennium-II run, combined with a sophisticated semi-analytical galaxy formation model, to explore statistically whether the local void is allowed within our current knowledge of galaxy formation in $\Lambda$CDM. We find that about $15$ percent of the Local Group analogue systems ($11$ of $77$) in our simulation are associated with nearby low density regions having size and ’emptiness’ similar to those of the observed Local Void. This suggests that, rather than a crisis of the $\Lambda$CDM, the emptiness of the Local Void is indeed a success of the standard $\Lambda$CDM theory. The paucity of faint galaxies in such voids results from a combination of two factors: a lower amplitude of the halo mass function in the voids than in the field, and a lower galaxy formation efficiency in void haloes due to halo assembly bias effects. While the former is the dominated factor, the later also plays a sizable role. The halo assembly bias effect results in a stellar mass fraction 25 percent lower for void galaxies when compared to field galaxies with the same halo mass.
Tue, 28 Jan 14
45/73
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