Radial velocity dispersion vs. age for Apollo (upper panel), Selene (middle panel), and Oceanus (bottom panel) disc stars, colour-coded according to their radial positions. Blue: region 1: inner region (one disc scale-length width, h_in using the SDSS r-band mock images from SUNRISE Jonsson 2006; these mock images can be seen in Few et al. 2012). Red: region 2: a 1-h_in width annulus between the centre and the 10⁷ M_⊙kpc^-2 mass surface density. Green: region 3: a 1-h_in width annulus centred at the 10⁷ M_⊙kpc^-2 mass surface density. Black: A 3.5-h_in width annulus further out (see text, Table 2, and Fig. 4 for further details). The parameter h_in is 2.34, 5.67, and 8.07 kpc for Apollo, Selene, and Oceanus, respectively. The parameter t_jump is denoted for each galaxy with dashed cyan vertical lines (the moment when the last main satellite is accreted). This plot is aimed at illustrating different epochs for different galaxies when the last major accretion event happened. Dashed lines show the AVR at intermediate simulation stages between the formation of the galaxy and the present day to address the effect of the last merger episode in the AVR (1.49 Gyr ago for Apollo, 4.34 for Selene, and 5.75 Gyr for Oceanus).