  Extreme emission line galaxies (EELGs), where nebular emissions contribute
30-40% of the flux in certain photometric bands, are ubiquitous in the early
universe (z>6). We utilise deep NIRCam imaging from the JWST Advanced Deep
Extragalactic Survey (JADES) to investigate the properties of companion
galaxies (projected distance <40 kpc, |dv|<10,000 km/s) around EELGs at z~3.
Tests with TNG100 simulation reveal that nearly all galaxies at z=3 will merge
with at least one companion galaxy selected using similar parameters by z=0.
The median mass ratio of the most massive companion and the total mass ratio of
all companions around EELGs is more than 10 times higher than the control
sample. Even after comparing with a stellar mass and stellar mass plus specific
SFR-matched control sample, EELGs have three-to-five times higher mass ratios
of the brightest companion and total mass ratio of all companions. Our
measurements suggest that EELGs are more likely to be experiencing strong
interactions or undergoing major mergers irrespective of their stellar mass or
specific SFRs. We suspect that gas cooling induced by strong interactions
and/or major mergers could be triggering the extreme emission lines, and the
increased merger rate might be responsible for the over-abundance of EELGs at
z>6.
