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Active galactic nuclei (AGN), particularly the most luminous AGN, arecommonly assumed to be triggered through major mergers, however observationalevidence for this scenario is mixed. To investigate any influence of galaxymergers on AGN triggering and luminosities through cosmic time, we present asample of 106 luminous X-ray selected type 1 AGN from the COSMOS survey. TheseAGN occupy a large redshift range (0.5 < z < 2.2) and two orders of magnitudein X-ray luminosity ($\sim$10$^{43}$ - 10$^{45}$ erg s$^{-1}$). AGN hosts arecarefully mass and redshift matched to 486 control galaxies. A novel techniquefor identifying and quantifying merger features in galaxies is developed,subtracting GALFIT galaxy models and quantifying the residuals. Comparison tovisual classification confirms this measure reliably picks out disturbancefeatures in galaxies. No enhancement of merger features with increasing AGNluminosity is found with this metric, or by visual inspection. We analyse theredshift evolution of AGN associated with galaxy mergers and find no mergerenhancement in lower redshift bins. Contrarily, in the highest redshift bin(z$\sim$2) AGN are $\sim$4 times more likely to be in galaxies exhibitingevidence of morphological disturbance compared to control galaxies, at 99%confidence level ($\sim$2.4$\sigma$) from visual inspection. Since only$\sim$15% of these AGN are found to be in morphologically disturbed galaxies,it is implied that major mergers at high redshift make a noticeable butsubdominant contribution to AGN fuelling. At low redshifts other processesdominate and mergers become a less significant triggering mechanism.

The redshift evolution of major merger triggering of luminous AGN: a slight enhancement at z$\sim$2