of baryons in structure formation, are more easy to constrain than cosmological solutions, and moreover do not request one to reject the $\Lambda$CDM paradigm.

While it is not complicated to separately solve the MSP problem, and the TBTF problem with the recipes discussed above, a simultaneous solution of both problems in models of galaxy formation based on DM-only simulations of the $\Lambda$CDM model (Boylan-Kolchin, Bullock & Kaplinghat 2012)[^5], is much more complicated.

Previous attempts to find a simultaneous solution to the abundance problem of satellites (MSP), and to the TBTF problem were made by the above mentioned Z12, and B13. Z12 found a correction to the velocity in the central kpc of galaxies, $\Delta v_{{\rm c,1kpc}}$, that mimicked the flattening of the cusp due to SF and tidal stripping.

This correction, together with its subsequent destruction effects from the tidal field of the baryonic disc, and the identification of subhaloes that remain dark because of their inefficiency in forming stars due to UV heating, were then applied by B13 to the subhaloes of the VL2 simulation (Diemand et al. 2008). As a result, the number of massive subhaloes in the VL2 were brought in line with the number of satellites 