Evolution of different system properties computed inside a spherical radius of 50 kpc on the B-band luminous centre of the simulation matching the global properties of the NGC 3447A/NGC 3447 system. Both panels stop at the actual age of the galaxy, that is, 12 Gyr (Sect. 4). Left: the gas accretion history; the (blue) dashed and (red) dotted lines correspond to the gas with temperature ≤10⁴ K and >10⁶ K respectively. Right: the SFR (blue solid line) and its behaviour averaging within 1 Gyr (red bins).