CFHT MegaPrime/MegaCam $u$-band source catalogue of the $AKARI$ North
  Ecliptic Pole Wide field
  The $AKARI$ infrared (IR) space telescope conducted two surveys (Deep and
Wide) in the North Ecliptic Pole (NEP) field to find more than 100,000 IR
sources using its Infrared Camera (IRC). IRC's 9 filters, which cover wavebands
from 2 to 24 $\mu$m continuously, make $AKARI$ unique in comparison with other
IR observatories such as $Spitzer$ or $WISE$. However, studies of the $AKARI$
NEP-Wide field sources had been limited due to the lack of follow-up
observations in the ultraviolet (UV) and optical. In this work, we present the
Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam $u$-band source
catalogue of the $AKARI$ NEP-Wide field. The observations were taken in 7
nights in 2015 and 2016, resulting in 82 observed frames covering 3.6 deg$^2$.
The data reduction, image processing and source extraction were performed in a
standard procedure using the \textsc{Elixir} pipeline and the
\textsc{AstrOmatic} software, and eventually 351,635 sources have been
extracted. The data quality is discussed in two regions (shallow and deep)
separately, due to the difference in the total integration time (4,520 and
13,910 seconds). The 5$\sigma$ limiting magnitude, seeing FWHM, and the
magnitude at 50 per cent completeness are 25.38 mag (25.79 mag in the deep
region), 0.82 arcsec (0.94 arcsec) and 25.06 mag (25.45 mag), respectively. The
u-band data provide us with critical improvements to photometric redshifts and
UV estimates of the precious infrared sources from the $AKARI$ space telescope.
