  Research over the past decade has shown diminishing empirical evidence for
major galaxy mergers being a dominating or even important mechanism for the
growth of supermassive black holes in galaxies and the triggering of optically
or X-ray selected active galactic nuclei (AGN). We here for the first time test
whether such a connection exists at least in the most plausible part of
parameter space for this mechanism: the highest specific accretion rate
broad-line AGNs at the peak epoch of black hole activity around z = 2. To that
end we examine 21 galaxies hosting a high accreting black hole (L/Ledd > 0.7)
observed with HST/WFC3 and 92 stellar mass- and redshift- matched inactive
galaxies taken from the CANDELS survey. We removed the AGN point sources from
their host galaxies and avoided bias in visual classification by adding and
then subtracting mock point sources to and from the comparison galaxies,
producing matched residual structures for both sets. The resulting samples were
joined, randomized, and subsequently visually ranked with respect to perceived
strength of structural distortions by 10 experts. The ensuing individual
rankings were combined into a consensus sequence and from this we derived
merger fractions for both samples. With the merger fractions f$_{m,agn}$ = 0.24
$\pm$ 0.09 for the AGN host galaxy sample and f$_{m,ina}$ = 0.19 $\pm$ 0.04 for
the inactive galaxies, we find no significant difference between the AGN host
galaxies and inactive galaxies. Also, both samples display comparable fractions
of disk-dominated galaxies. These findings are consistent with previous studies
for different AGN populations, and we conclude that even black hole growth at
the highest specific accretion rates and at the peak of cosmic AGN activity is
not predominantly caused by major mergers. (abriged)
