The abundance of satellite galaxies in the inner region of ΛCDM Milky Way sized haloes

Abstract

The concordance lambda cold dark matter (ΛCDM) cosmology predicts tens of satellite galaxies distributed in the inner region (<40 kpc) of the Milky Way (MW), yet at most 12 were discovered at present day, including three discovered very recently by Dark Energy Survey (DES) and five from other surveys (e.g. PanSTARRS, MagLiteS). We use five ultra-high resolution simulations of MW-sized dark matter haloes from the AQUARIUS project, combined with GALFORM semi-analytical galaxy formation model, to investigate properties of the model satellite galaxy population inside 40 kpc of MW-sized haloes. On average, in each halo this model predicts about 20 inner satellite galaxies, among them five are comparable to the classic satellites in the luminosity, these are in stark contrast to the corresponding numbers in observations. We further investigate the survivability of these model inner satellites in the presence of a central stellar disc with a set of ideal simulations. These are done by re-evolving a quarter (30) of the whole AQUARIUS inner satellite galaxies (121) by including a static disc potential in addition to the MW halo. Our finding is that the additional disc completely disrupts 40 per cent of these satellites and results in 14 satellite galaxies within the 40 kpc of each AQUARIUS at the end, in reasonably well agreement with observations.