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tokens: history. On the other hand, galaxies MW c and M31 c are the MW and M31 candidates of Nuza et al. ( 2014 ) (see also Scannapieco et al. 2015 ) that were extracted from a WMAP -5 cosmological simulation of the Local Group. As a result, these galaxies reside in an environment more similar to the actual one. The main properties of each model galaxy at = 0 are shown in Table 1 . The latter also includes a scaled-down version of g106, referred to as g106r, that was used as an MW candidate by MCM13 and MCM14 in their Galactic chemodynamical model. More details concerning the galaxies, as well as the main assumptions and techniques adopted to perform each simulation, can be found below. Table 1. Properties of the simulated galaxies at = 0. The columns show virial mass, virial radius, stellar mass (within optical radius), optical radius, bulge-to-total ratio, and references. Note . a Rescaled g106 used as an MW proxy by MCM13 and MCM14 (see Section 4.3 ). 2.1 g37 and g106 These galaxies are selected from the larger galaxy sample of Martig et al. ( 2012 ). The simulation technique involves basically two steps (see Martig et al. 2009 , for technical details). First, a dark-matter-only simulation is performed in a box of Mpc on a side using the adaptive mesh refinement RAMSES code (Teyssier 2002 ) to extract merger and accretion histories for the target haloes. Some properties such as time, mass, velocity, and spin of incoming satellites are then stored. In the second step, a new simulation is performed in which each halo recorded in the dark-matter-only run is replaced by a model galaxy made up of gas, stars, and dark-matter particles. Similarly, each diffuse particle of the cosmological simulation is replaced with a blob of higher-resolution gas and dark-matter particles. These model ‘seed’ galaxies are made up of a disc containing gas and stars, a stellar bulge, and a dark-matter halo following analytical prescriptions for the profiles in each case. The stellar mass of a galaxy in the simulation is set according to the Moster et al. ( 2010 ) relation as a function of halo mass and redshift. All model galaxies are assumed to be disc galaxies without a bulge, except for the most massive haloes with M ⊙ at 1, in which case the mass of the bulge is set to of the stellar mass. The gas content in the disc is also set according to an analytical scheme: at 1, the gas fraction (with respect to the total baryonic mass) is 0.3 for small galaxies ( M ⊙ ) and 0.15 for the massive ones. At higher redshifts, the gas fraction is chosen independently of the total mass, and is set to 0.5 for 1 3 and 0.7 for > 3. No hot gas halo is included, which should be a sensible approximation only for halo masses lower than a critical mass of M ⊙ , which is required for virial shocks to be stable (e.g. Birnboim Dekel 2003 ). The resimulation starts at = 5 inside a region of radius 800 kpc, i.e. spanning a few times the virial radius value of the main galaxy at = 0, and follows its