Top: probability distribution of the mass-to-light ratios observed when nebular emission is included in the fitting, stacked across all of the MC samples. Top: probability distribution of the mass-to-light ratios observed when nebular emission is included in the fitting, stacked across all of the MC samples. The values are normalized such that the probability at each value of MUV integrates to unity The blue dot–dashed line represents the average of the best-fitting line to robust means in each of the MC samples, with the corresponding average means and their errors shown by the blue circles. The z ∼ 4 relation is shown for reference at high redshifts (cyan dotted line). Bottom: the corresponding probability distributions, bi-weight means and best-fitting relation (red dot–dashed line) when nebular emission is excluded from the SED fitting. The blue dotted line shows the best-fitting relation from the top panel (including nebular emission) for each sample. In both panels, the orange dashed line shows the mass-to-light ratio observed by González et al. (2011), measured for their z ≈ 4 sample and applied across all bins. The green triangles and yellow squares show the average stellar mass in MUV bins as calculated by Lee et al. (2012) and Stark et al. (2009), respectively, all stellar masses have been converted to the same Chabrier IMF. The grey dotted line represents the template in our SED fitting parameters with the lowest mass-to-light ratio. K. Duncan et al. MNRAS 2014;444:2960-2984 © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society