Cumulative distribution of V-band magnitude for satellite galaxies in each simulated MW system (black curves). The red dot-dashed line shows the equivalent distribution for known Milky Way satellites and the red dashed line the average distribution for Milky Way and M31 satellites corrected for completeness and sky coverage by Koposov et al. (2008). 

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... the last section we have shown that our model predicts a typi- cal halo mass for Milky Way analogues in the same range as re- cent measurements of the Milky Way galaxy itself. In this sec- tion, we will focus on the properties and spatial distribution of satellite galaxies around the Milky Way. As mentioned in Sec. 2, the mass resolution of the COCO simulation is 60 times higher than that of MS-II, and the spatial resolution is higher by a fac- tor of 4. More than 90% of satellites in Mikly Way systems with Vmax > 15 km s −1 still have their own subhaloes in COCO, which allows us to follow their evolution in detail (see Appendix). This level of resolution is especially important for studying the internal dynamics and structure of satellite galaxies. For example, their ro- tation curves can be traced reliably and hence Vmax can be used as a robust measure of the depth of their potential. Therefore, in the following sections, we only use the COCO simulation to study the properties of satellite systems. Fig. 2 shows cumulative counts of satellite galaxies as a function of V-band magnitude around the 13 simulated MW analogues se- lected from COCO (black curves). The red dot-dashed curve repre- sents the equivalent luminosity function of known satellites around the Milky Way and the dashed curve shows the average luminosity function of satellites in the MW and M31 found by Koposov et al. (2008), who attempted to correct for incompletness and partial sky coverage. For this comparison, following Koposov et al., we de- fine all galaxies within 280 kpc of each MW analogue as its satel- lites. The model predictions are broadly consistent with the data although the slope at the faint end is steeper in the simulations than in the data. This demonstrates convergence with the results of Guo et al. (2011), who showed that the bright end of the V-band satllite luminosity function for the much larger number of MW analogues in MS-II is also in reasonable agreement with the MW and M31 systems 2 . Fig. 3 compares the galactocentric radial distribution of the most luminous satellites around our Milky Way analogues to those in the real Milky Way system. We restrict this comparison to the 'classical' brightest 12 satellites, using the galactocentric distances given by McConnachie (2012). These observed satellites galaxies are brighter than MV ≈ −9, so we select simulated satellite galax- ies with MV < −9 for this comparison. The Milky Way obser- vations lie within the envelope of the radial distributions from our ...