Boötes-HiZELS: An optical to near-infrared survey of emission-line galaxies at z = 0.4-4.7

Jorryt Matthee, David Sobral, Philip Best, Ian Smail, Fuyan Bian, Behnam Darvish, Huub Röttgering, Xiaohui Fan

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


We present a sample of~1000 emission-line galaxies at z=0.4-4.7 from the~0.7deg2 High-z Emission-Line Survey in the Boötes field identified with a suite of six narrow-band filters at ≈0.4-2.1 μm. These galaxies have been selected on their Lyα (73), [OII] (285), Hβ/[OIII] (387) or Hα (362) emission line, and have been classified with optical to near-infrared colours. A subsample of 98 sources have reliable redshifts from multiple narrow-band (e.g. [OII]-Hα) detections and/or spectroscopy. In this survey paper, we present the observations, selection and catalogues of emitters. We measure number densities of Lyα, [OII], Hβ/[OIII] and Hα and confirm strong luminosity evolution in star-forming galaxies from z ~ 0.4 to ~5, in agreement with previous results. To demonstrate the usefulness of dual-line emitters, we use the sample of dual [OII]-Hα emitters to measure the observed [OII]/Hα ratio at z = 1.47. The observed [OII]/Hα ratio increases significantly from 0.40±0.01 at z = 0.1 to 0.52±0.05 at z = 1.47, which we attribute to either decreasing dust attenuation with redshift, or due to a bias in the (typically) fibre measurements in the local Universe that only measure the central kpc regions. At the bright end, we find that both the Hα and Lyα number densities at z ≈ 2.2 deviate significantly from a Schechter form, following a power law. We show that this is driven entirely by an increasing X-ray/active galactic nucleus fraction with line luminosity, which reaches ≈100 per cent at line luminosities L ≳ 3 × 1044 erg s-1.

Original languageEnglish (US)
Pages (from-to)629-649
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Oct 11 2017


  • Galaxies: active
  • Galaxies: evolution
  • Galaxies: high-redshift
  • Galaxies: luminosity function
  • Galaxies: star formation
  • Mass function

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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