Boötes-HiZELS: An optical to near-infrared survey of emission-line galaxies at z = 0.4–4.7 Matthee, Jorryt J ; https://orcid.org/0000-0003-2871-127X Sobral, David Best, Philip Smail, Ian Bian, Fuyan Darvish, Behnam Röttgering, Huub Fan, Xiaohui Space and Planetary Science Astronomy and Astrophysics galaxies active galaxies evolution galaxies high-redshift galaxies luminosity function mass function galaxies: star formation 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 Ly α (73), [O II] (285), H β/[O III] (387) or H α (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. [O II]–H α) detections and/or spectroscopy. In this survey paper, we present the observations, selection and catalogues of emitters. We measure number densities of Ly α, [O II], H β/[O III] and H α 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 [O II]–H α emitters to measure the observed [O II]/H α ratio at z = 1.47. The observed [O II]/H α 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 H α and Ly α 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. Oxford University Press 2017 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/11561 Matthee JJ, Sobral D, Best P, et al. Boötes-HiZELS: An optical to near-infrared survey of emission-line galaxies at z = 0.4–4.7. <i>Monthly Notices of the Royal Astronomical Society</i>. 2017;471(1):629-649. doi:<a href="https://doi.org/10.1093/mnras/stx1569">10.1093/mnras/stx1569</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1093/mnras/stx1569 info:eu-repo/semantics/altIdentifier/issn/0035-8711 info:eu-repo/semantics/altIdentifier/issn/1365-2966 info:eu-repo/semantics/altIdentifier/arxiv/1702.04721 info:eu-repo/semantics/openAccess