CF-HiZELS, an ∼10 deg2 emission-line survey with spectroscopic follow-up : Hα, [O III] + Hβ and [O II] luminosity functions at z = 0.8, 1.4 and 2.2

Sobral, David and Matthee, Jorryt and N. Best, Philip and Smail, Ian and A. Khostovan, Ali and Milvang-Jensen, Bo and Kim, Jae-Woo and Stott, John and Calhau, Joao and Nayyeri, Hooshang and Mobasher, Bahram (2015) CF-HiZELS, an ∼10 deg2 emission-line survey with spectroscopic follow-up : Hα, [O III] + Hβ and [O II] luminosity functions at z = 0.8, 1.4 and 2.2. Monthly Notices of the Royal Astronomical Society, 451 (3). pp. 2303-2323. ISSN 0035-8711

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$0.005 \mu m) to survey ~10 deg$^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 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.