We use a large sample of \sim 350 , 000 galaxies constructed by combining the UKIDSS UDS , VIDEO/CFHT-LS , UltraVISTA/COSMOS and GAMA survey regions to probe the major ( 1:4 stellar mass ratio ) merging histories of massive galaxies ( > 10 ^ { 10 } \mathrm { M } _ { \odot } ) at 0.005 < z < 3.5 .
We use a method adapted from that presented in \citet Lopez-Sanjuan2014 , using the full photometric redshift probability distributions , to measure pair fractions of flux-limited , stellar mass selected galaxy samples using close-pair statistics .
The pair fraction is found to weakly evolve as \propto ( 1 + z ) ^ { 0.8 } with no dependence on stellar mass .
We subsequently derive major merger rates for galaxies at > 10 ^ { 10 } \mathrm { M } _ { \odot } and at a constant number density of n > 10 ^ { -4 } Mpc ^ { -3 } , and find rates a factor of 2–3 smaller than previous works , although this depends strongly on the assumed merger timescale and likelihood of a close-pair merging .
Galaxies undergo approximately 0.5 major mergers at z < 3.5 , accruing an additional 1–4 \times 10 ^ { 10 } \mathrm { M } _ { \odot } in the process .
On average this represents an increase in stellar mass of 20–30 % ( 40–70 % ) for constant stellar mass ( constant number density ) samples .
Major merger accretion rate densities of \sim 2 \times 10 ^ { -4 } \mathrm { M } _ { \odot } yr ^ { -1 } Mpc ^ { -3 } are found for number density selected samples , indicating that direct progenitors of local massive ( > 10 ^ { 11 } \mathrm { M } _ { \odot } ) galaxies have experienced a steady supply of stellar mass via major mergers throughout their evolution .
While pair fractions are found to agree with those predicted by the \citet Henriques2014 semi-analytic model , the Illustris hydrodynamical simulation fails to quantitatively reproduce derived merger rates .
Furthermore , we find major mergers become a comparable source of stellar mass growth compared to star-formation at z < 1 , but is 10–100 times smaller than the SFR density at higher redshifts .