Abstract
We present results from the largest contiguous narrow-band survey in the
near-infrared. We have used WIRCam/CFHT and the lowOH2 filter (1.187$\pm$0.005
m) to survey ~10 deg$^2$ of contiguous extragalactic sky in the SA22 field.
A total of ~6000 candidate emission-line galaxies are found. We use deep CFHTLS
$ugriz$ and UKIDSS DXS $J$ and $K$ data to obtain robust photometric redshifts.
We combine our data with HiZELS (COSMOS+UDS) and explore VVDS, VIPERS, KMOS and
obtain our own spectroscopic follow-up with FMOS and MOSFIRE to derive large
samples of high-redshift emission-line selected galaxies: 3471 H\alpha\
emitters at z=0.8, 1343 OIII+H\beta\ emitters at z=1.4 and 572 OII emitters
at z=2.2. We probe co-moving volumes of >10$^6$ Mpc$^3$ and find significant
over-densities, including an 8.5\sigma\ (spectroscopically confirmed)
over-density of H\alpha\ emitters at z=0.81. We derive H\alpha, OIII+H\beta\
and OII luminosity functions at z=0.8, 1.4 and 2.2, respectively, and present
implications for future surveys such as EUCLID. Our uniquely large
volumes/areas allow us to sub-divide the samples in thousands of randomised
combinations of areas and provide a robust empirical measurement of
sample/cosmic variance. We show that surveys for star-forming/emission-line
galaxies at a depth similar to ours can only overcome cosmic-variance (errors
<10%) if they are based on volumes >5x10$^5$ Mpc$^3$; errors on L$^*$ and
\Phi$^*$ due to sample (cosmic) variance on surveys probing ~10$^4$ Mpc$^3$
and ~10$^5$ Mpc$^3$ are typically very high: ~300% and ~40-60%, respectively.
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