Star formation at z=1.47 from HiZELS: An H{\alpha}+[OII] double-blind
  study
  This paper presents the results from the first wide and deep dual narrow-band
survey to select H-alpha (Ha) and [OII] line emitters at z=1.47+-0.02 (using
matched narrow-band filters in the H and z' bands), exploiting synergies
between the UKIRT and Subaru telescopes. The Ha survey at z=1.47 reaches a flux
limit of ~7x10^-17 erg/s/cm^2 and detects ~200 Ha emitters over 0.7deg^2, while
the much deeper [OII] survey reaches an effective flux of ~7x10^-18 erg/s/cm^2,
detecting ~1400 z=1.47 [OII] emitters in a matched co-moving volume of
~2.5x10^5 Mpc^3. The combined survey results in the identification of 190
simultaneous Ha and [OII] emitters at z=1.47. Ha and [OII] luminosity functions
are derived and both are shown to evolve significantly from z~0 in a consistent
way. The star formation rate density of the Universe at z=1.47 is evaluated,
with the Ha analysis yielding 0.16+-0.05 M_sun/yr/Mpc^3 and the [OII] analysis
0.17+-0.04 M_sun/yr/Mpc^3. The measurements are combined with other studies,
providing a self-consistent measurement of the star formation history of the
Universe over the last ~11Gyrs. By using a large comparison sample at z~0.1
(from the SDSS), [OII]/Ha line ratios are calibrated as probes of
dust-extinction. Ha emitters at z~1.47 show on average 1 mag of extinction at
Ha, similar to the SDSS sources at z~0. Although we find that dust extinction
correlates with SFR, the relation evolves by about ~0.5 mag from z~1.5 to z~0,
with z~0 relations over-predicting the dust extinction corrections at high-z by
that amount. Stellar mass is found to be a much more fundamental extinction
predictor, with the relation between mass and extinction being valid at both
z~0 and z~1.5. Dust extinction corrections as a function of optical colours are
also derived, offering simpler mechanisms for estimating extinction in
moderately star-forming systems over the last ~9Gyrs [Abridged].
