Major mergers are not significant drivers of star formation or
  morphological transformation around the epoch of peak cosmic star formation
  We investigate the contribution of major mergers (mass ratios $>1:5$) to
stellar mass growth and morphological transformations around the epoch of peak
cosmic star formation ($z\sim2$). We visually classify a complete sample of
massive (M $>$ 10$^{10}$M$_{\odot}$) galaxies at this epoch, drawn from the
CANDELS survey, into late-type galaxies, major mergers, spheroids and disturbed
spheroids which show morphological disturbances. Given recent simulation work,
which indicates that recent ($<$0.3-0.4 Gyr) major-merger remnants exhibit
clear tidal features in such images, we use the fraction of disturbed spheroids
to probe the role of major mergers in driving morphological transformations.
The percentage of blue spheroids (i.e. with ongoing star formation) that show
morphological disturbances is only 21 $\pm$ 4%, indicating that major mergers
are not the dominant mechanism for spheroid creation at $z\sim2$ - other
processes, such as minor mergers or cold accretion are likely to be the main
drivers of this process. We also use the rest-frame U-band luminosity as a
proxy for star formation to show that only a small fraction of the star
formation budget ($\sim$3%) is triggered by major mergers. Taken together, our
results show that major mergers are not significant drivers of galaxy evolution
at $z\sim2$.
