Circularised mass-to-light ratio Υ_⋆r as a function of the radius for NGC 1277 and NGC 1278, in blue and red respectively. The vertical lines indicate the limit of the GCMS kinematic data, The right axis shows the correspondence with the absolute value of the outer exponent of a bimodal IMF, Γ_b, for a stellar population with an age of 13.0 Gyr and a metallicity [Z/H] = 0.26. The horizontal black dashed lines denote the range of Γ_b values found by Martín-Navarro et al. (2015) for NGC 1277, with the upper line (Γ_b = 3.25) corresponding to their upper limit for the inner parts of the galaxy and the lower line (Γ_b = 2.15) corresponding to their lower limit at a radius R = 1.4 R_e. The surface brightness of NGC 1278 has been converted to F625W as in Sect. 3.2. The correspondence between Υ_⋆r and Γ_b is only roughly valid for NGC 1277 because NGC 1278 is slightly younger and less metallic (Ferré-Mateu et al., in prep.).