Comparison of the stellar mass measurements obtained using GOSSIP+ on the 180 000 simulated sample with the input values. Top panel: the density plot represents the measurement of M_⋆ from the combined fit versus the input M_⋆. The highest density is represented by the brightest colour, while the lowest density is represented in black. The blue line represents the 1σ contour of the distribution. The combined fit is able to find the correct M_⋆ at any mass in the simulated range. Bottom panel: evolution of the quantity over the stellar mass range. The points in red, green, and blue represent the fit on the spectroscopy only, photometry only and on the combined data, respectively. The combined fit leads to the most accurate M_⋆ computation with ΔM_⋆< 0.1 dex.