We use the Galaxy And Mass Assembly ( GAMA ) survey to measure the local Universe mass dependent merger fraction and merger rate using galaxy pairs and the CAS structural method , which identifies highly asymmetric merger candidate galaxies .
Our goals are to determine which types of mergers produce highly asymmetrical galaxies , and to provide a new measurement of the local galaxy major merger rate .
We examine galaxy pairs at stellar mass limits down to M _ { * } = 10 ^ { 8 } M _ { \odot } with mass ratios of < 100:1 and line of sight velocity differences of \Delta V < 500 km s ^ { -1 } .
We find a significant increase in mean asymmetries for projected separations less than the sum of the individual galaxy ’ s Petrosian 90 radii .
For systems in major merger pairs with mass ratios of < 4:1 both galaxies in the pair show a strong increase in asymmetry , while in minor merger systems ( with mass ratios of > 4:1 ) the lower mass companion becomes highly asymmetric , while the larger galaxy is much less affected .
The fraction of highly asymmetric paired galaxies which have a major merger companion is highest for the most massive galaxies and drops progressively with decreasing mass .
We calculate that the mass dependent major merger fraction is fairly constant at \sim 1.3 - 2 \% between 10 ^ { 9.5 } < M _ { * } < 10 ^ { 11.5 } M _ { \odot } , and increases to \sim 4 \% at lower masses .
When the observability time scales are taken into consideration , the major merger rate is found to approximately triple over the mass range we consider .
The total co-moving volume major merger rate over the range 10 ^ { 8.0 } < M _ { * } < 10 ^ { 11.5 } M _ { \odot } is ( 1.2 \pm 0.5 ) \times 10 ^ { -3 } h ^ { 3 } _ { 70 } Mpc ^ { -3 } Gyr ^ { -1 } .