  While supermassive black holes are ubiquitous features of galactic nuclei,
only a small minority are observed during episodes of luminous accretion. The
physical mechanism(s) driving the onset of fueling and ignition in these active
galactic nuclei (AGN) are still largely unknown for many galaxies and
AGN-selection criteria. Attention has focused on AGN triggering by means of
major galaxy mergers gravitationally funneling gas towards the galactic center,
with evidence both for and against this scenario. However, several recent
studies have found that radio-loud AGN overwhelmingly reside in ongoing or
recent major galaxy mergers. In this study, we test the hypothesis that major
galaxy mergers are important triggers for radio-loud AGN activity in powerful
quasars during cosmic noon (1 < z < 2). To this end, we compare Hubble Space
Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars
to three matched radio-quiet quasar control samples. We find strong evidence
for major-merger activity in nearly all radio-loud AGN, in contrast to the much
lower merger fraction in the radio-quiet AGN. These results suggest major
galaxy mergers are key ingredients to launching powerful radio jets. Given many
of our radio-loud quasars are blue, our results present a possible challenge to
the "blow-out" paradigm of galaxy evolution models in which blue quasars are
the quiescent end result following a period of red quasar feedback initiated by
a galaxy merger. Finally, we find a tight correlation between black hole mass
and host galaxy luminosity for these different high-redshift AGN samples
inconsistent with those observed for local elliptical galaxies.
