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Aims. We aim to perform consistent comparisons between observations andsimulations on the mass dependence of the galaxy major merger fraction at lowredshift over an unprecedentedly wide range of stellar masses (10^9 to 10^12solar masses).  Methods. We first carry out forward modelling of ideal synthetic images ofmajor mergers and non-mergers selected from the Next Generation IllustrisSimulations (IllustrisTNG) to include major observational effects. We thentrain deep convolutional neural networks (CNNs) using realistic mockobservations of galaxy samples from the simulations. Subsequently, we apply thetrained CNNs to real the Kilo-Degree Survey (KiDS) images of galaxies selectedfrom the Galaxy And Mass Assembly (GAMA) survey. Based on the major mergersamples, which are detected in a consistent manner in the observations andsimulations, we determine the dependence of major merger fraction on stellarmass at z around 0.15 and make comparisons between the two.  Results. The detected major merger fraction in the GAMA/KiDS observations hasa fairly mild decreasing trend with increasing stellar mass over the mass range10^9 < M_sun < M_star < 10^11.5 M_sun. There is good agreement in the massdependence of the major merger fraction in the GAMA/KiDS observations and theIllustrisTNG simulations over 10^9.5 M_sun < M_star < 10^10.5 M_sun. However,the observations and the simulations show some differences at M_star >10^10.5M_sun, possibly due to the supermassive blackhole feedback in itslow-accretion state in the simulations which causes a sharp transition in thequenched fractions at this mass scale. The discrepancy could also be due to therelatively small volume of the simulations and/or differences in how stellarmasses are measured in simulations and observations.

Towards a consistent framework of comparing galaxy mergers in observations and simulations