It is still a challenge to assess the merger fraction of galaxies at different cosmic epochs in order to probe the evolution of their mass assembly .
Using the Illustris cosmological simulation project , we investigate the relation between the separation of galaxies in a pair , both in velocity and projected spatial separation space , and the probability that these interacting galaxies will merge in the future .
From this analysis , we propose a new set of criteria to select close pairs of galaxies along with a new corrective term to be applied to the computation of the galaxy merger fraction .
We then probe the evolution of the major and minor merger fraction using the latest MUSE deep observations over the Hubble Ultra Deep Field , Hubble Deep Field South , COSMOS-Gr30 and Abell 2744 regions .
From a parent sample of 2483 galaxies with spectroscopic redshifts , we identify 366 close pairs spread over a large range of redshifts ( 0.2 < z < 6 ) and stellar masses ( 10 ^ { 7 } -10 ^ { 11 } \mbox { M } _ { \sun } ) .
Using the stellar mass ratio between the secondary and primary galaxy as a proxy to split the sample into major , minor and very minor mergers , we found a total of 183 major , 142 minor and 47 very minor close pairs corresponding to a mass ratio range of 1:1-1:6 , 1:6-1:100 and lower than 1:100 , respectively .
Due to completeness issues , we do not consider the very minor pairs in the analysis .
Overall , the major merger fraction increases up to z \approx 2 - 3 reaching 25 % for pairs with the most massive galaxy with a stellar mass \mbox { M } ^ { \star } \geq 10 ^ { 9.5 } \mbox { M } _ { \sun } .
Beyond this redshift , the fraction decreases down to \sim 5 % at z \approx 6 .
The major merger fraction for lower mass primary galaxies \mbox { M } ^ { \star } \leq 10 ^ { 9.5 } \mbox { M } _ { \sun } , seems to follow a more constant evolutionary trend with redshift .
Thanks to the addition of new MUSE fields and new selection criteria , the increased statistics of the pair samples allow to narrow significantly the error bars compared to our previous analysis ( Ventou et al .
2017 ) .
The evolution of the minor merger fraction is roughly constant with cosmic time , with a fraction of 20 % at z < 3 and a slow decrease between 3 \leq z \leq 6 to 8 - 13 % .