{
  "id": "1601.02266",
  "version": "v1",
  "published": "2016-01-10T21:00:00.000Z",
  "updated": "2016-01-10T21:00:00.000Z",
  "title": "The most luminous H$α$ emitters at z~0.8-2.23 from HiZELS: evolution of AGN and star-forming galaxies",
  "authors": [
    "David Sobral",
    "Saul A. Kohn",
    "Philip N. Best",
    "Ian Smail",
    "Chris M. Harrison",
    "John Stott",
    "João Calhau",
    "Jorryt Matthee"
  ],
  "comment": "16 pages, 10 figures. Accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We use new near-infrared spectroscopic observations to investigate the nature and evolution of the most luminous H\\alpha (Ha) emitters at z~0.8-2.23, which evolve strongly in number density over this period, and compare them to more typical Ha emitters. We study 59 luminous Ha emitters with $L_{H\\alpha}>L_{H\\alpha}^*$, roughly equally split per redshift slice at z~0.8, 1.47 and 2.23 from the HiZELS and CF-HiZELS surveys. We find that, overall, 30$\\pm$8% are AGN (80$\\pm$30% of these AGN are broad-line AGN, BL-AGN), and we find little to no evolution in the AGN fraction with redshift, within the errors. However, the AGN fraction increases strongly with Ha luminosity and correlates best with $L_{H\\alpha}/L_{H\\alpha}^*(z)$. While $L_{H\\alpha}<L_{\\rm H\\alpha}^*(z)$ Ha emitters are largely dominated by star-forming galaxies (>80%), the most luminous Ha emitters ($L_{H\\alpha}>10L_{H\\alpha}^*(z)$) at any cosmic time are essentially all BL-AGN. Using our AGN-decontaminated sample of luminous star-forming galaxies, and integrating down to a fixed Ha luminosity, we find a factor of ~1300x evolution in the star formation rate density from z=0 to z=2.23. This is much stronger than the evolution from typical Ha star-forming galaxies and in line with the evolution seen for constant luminosity cuts used to select \"Ultra-Luminous\" Infrared Galaxies and/or sub-millimetre galaxies. By taking into account the evolution in the typical Ha luminosity, we show that the most strongly star-forming Ha-selected galaxies at any epoch ($L_{H\\alpha}>L^*_{H\\alpha}(z)$) contribute the same fractional amount of ~15% to the total star-formation rate density, at least up to z=2.23.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-01-10T21:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "star-forming galaxies",
      "ha luminosity",
      "luminous ha emitters",
      "typical ha",
      "total star-formation rate density"
    ],
    "publication": {
      "doi": "10.1093/mnras/stw022"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1414752
    }
  }
}