Slicing COSMOS with SC4K: The evolution of typical Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6 Sobral, David Santos, Sérgio Matthee, Jorryt J ; https://orcid.org/0000-0003-2871-127X Paulino-Afonso, Ana Ribeiro, Bruno Calhau, João Khostovan, Ali A Space and Planetary Science Astronomy and Astrophysics galaxies: evolution galaxies: formation galaxies: high-redshift galaxies: luminosity function mass function galaxies: statistics We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton Telescopes in the ∼2 deg2 COSMOS field. We use these data as an extremely wide, low-resolution (R ∼ 20–80) Integral Field Unit survey to slice through the COSMOS field and obtain a large sample of ∼4000 Ly α emitters (LAEs) from z ∼ 2 to 6 in 16 redshift slices (SC4K). We present new Ly α luminosity functions (LFs) covering a comoving volume of ∼108 Mpc3. SC4K extensively complements ultradeep surveys, jointly covering over 4 dex in Ly α luminosity and revealing a global (2.5 < z < 6) synergy LF with α=−1.93+0.12−0.12⁠, log10Φ∗Lyα=−3.45+0.22−0.29 Mpc−3, and log10L∗Lyα=42.93+0.15−0.11 erg s−1. The Schechter component of the Ly α LF reveals a factor ∼5 rise in L∗Lyα and a ∼7 × decline in Φ∗Lyα from z ∼ 2 to 6. The data reveal an extra power-law (or Schechter) component above LLy α ≈ 1043.3 erg s−1 at z ∼ 2.2–3.5 and we show that it is partially driven by X-ray and radio active galactic nucleus (AGN), as their Ly α LF resembles the excess. The power-law component vanishes and/or is below our detection limits above z > 3.5, likely linked with the evolution of the AGN population. The Ly α luminosity density rises by a factor ∼2 from z ∼ 2 to 3 but is then found to be roughly constant (⁠1.1+0.2−0.2×1040 erg s−1 Mpc−3) to z ∼ 6, despite the ∼0.7 dex drop in ultraviolet (UV) luminosity density. The Ly α/UV luminosity density ratio rises from 4 ± 1 per cent to 30 ± 6 per cent from z ∼ 2.2 to 6. Our results imply a rise of a factor of ≈2 in the global ionization efficiency (ξion) and a factor ≈4 ± 1 in the Ly α escape fraction from z ∼ 2 to 6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical interstellar medium conditions allowing Ly α photons to escape. Oxford University Press 2018 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/11558 Sobral D, Santos S, Matthee JJ, et al. Slicing COSMOS with SC4K: The evolution of typical Ly α emitters and the Ly α escape fraction from z ∼ 2 to 6. <i>Monthly Notices of the Royal Astronomical Society</i>. 2018;476(4):4725-4752. doi:<a href="https://doi.org/10.1093/mnras/sty378">10.1093/mnras/sty378</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1093/mnras/sty378 info:eu-repo/semantics/altIdentifier/issn/0035-8711 info:eu-repo/semantics/altIdentifier/e-issn/1365-2966 info:eu-repo/semantics/altIdentifier/arxiv/1712.04451 info:eu-repo/semantics/openAccess