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A 10 deg2 Lyman α survey at z=8.8 with spectroscopic follow-up: strong constraints on the luminosity function and implications for other surveys

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  • Jorryt J. A. Matthee
  • David Sobral
  • A. M. Swinbank
  • Ian Smail
  • P. N. Best
  • Jae Woo Kim
  • Marijn Franx
  • Bo Milvang-Jensen
  • Johan Fynbo
<mark>Journal publication date</mark>21/05/2014
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number3
Number of pages13
Pages (from-to)2375-2387
Publication StatusPublished
Early online date31/03/14
<mark>Original language</mark>English


Candidate galaxies at redshifts of z ~ 10 are now being found in extremely deep surveys, probing very small areas. As a consequence, candidates are very faint, making spectroscopic confirmation practically impossible. In order to overcome such limitations, we have undertaken the CF-HiZELS survey, which is a large-area, medium-depth near-infrared narrow-band survey targeted at z = 8.8 Lyman α (Lyα) emitters (LAEs) and covering 10 deg2 in part of the SSA22 field with the Canada-France-Hawaii Telescope (CFHT). We surveyed a comoving volume of 4.7 × 106 Mpc3 to a Lyα luminosity limit of 6.3 × 1043 erg s-1. We look for Lyα candidates by applying the following criteria: (i) clear emission-line source, (ii) no optical detections (ugriz from CFHTLS), (iii) no visible detection in the optical stack (ugriz > 27), (iv) visually checked reliable NBJ and J detections and (v) J - K ≤ 0. We compute photometric redshifts and remove a significant amount of dusty lower redshift line-emitters at z ~ 1.4 or 2.2. A total of 13 Lyα candidates were found, of which two are marked as strong candidates, but the majority have very weak constraints on their spectral energy distributions. Using follow-up observations with SINFONI/VLT, we are able to exclude the most robust candidates as LAEs. We put a strong constraint on the Lyα luminosity function at z ~ 9 and make realistic predictions for ongoing and future surveys. Our results show that surveys for the highest redshift LAEs are susceptible of multiple contaminations and that spectroscopic follow-up is absolutely necessary.