{
  "id": "1801.03942",
  "version": "v1",
  "published": "2018-01-11T19:00:02.000Z",
  "updated": "2018-01-11T19:00:02.000Z",
  "title": "Average [O II] nebular emission associated with Mg II absorbers: Dependence on Fe II absorption",
  "authors": [
    "Ravi Joshi",
    "Raghunathan Srianand",
    "Patrick Petitjean",
    "Pasquier Noterdaeme"
  ],
  "comment": "16 Pages, 5 Tables, 13 Figures (Accepted for the publication in MNRAS main Journal)",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We investigate the effect of Fe II equivalent width ($W_{2600}$) and fibre size on the average luminosity of [O II]$\\lambda\\lambda$3727,3729 nebular emission associated with Mg II absorbers (at $0.55 \\le z \\le 1.3$) in the composite spectra of quasars obtained with 3 and 2 arcsec fibres in the Sloan Digital Sky Survey. We confirm the presence of strong correlations between [O II] luminosity (L$_{[\\rm O~II]}$) and equivalent width ($W_{2796}$) and redshift of Mg II absorbers. However, we show L$_{[\\rm O~II]}$ and average luminosity surface density suffers from fibre size effects. More importantly, for a given fibre size the average L$_{[\\rm O~II]}$ strongly depends on the equivalent width of Fe II absorption lines and found to be higher for Mg II absorbers with $R \\equiv$ $W_{\\rm 2600}/W_{\\rm 2796}$ $\\ge 0.5$. In fact, we show the observed strong correlations of L$_{[\\rm O~II]}$ with $W_{2796}$ and $z$ of Mg II absorbers are mainly driven by such systems. Direct [O II] detections also confirm the link between L$_{[\\rm O~II]}$ and $R$. Therefore, one has to pay attention to the fibre losses and dependence of redshift evolution of Mg II absorbers on $W_{2600}$ before using them as a luminosity unbiased probe of global star formation rate density. We show that the [O II] nebular emission detected in the stacked spectrum is not dominated by few direct detections (i.e., detections $\\ge 3 \\sigma$ significant level). On an average the systems with $R$ $\\ge 0.5$ and $W_{2796}$ $\\ge 2$ \\AA\\ are more reddened, showing colour excess E($B-V$) $\\sim$ 0.02, with respect to the systems with $R$ $< 0.5$ and most likely traces the high H I column density systems.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-01-11T19:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nebular emission",
      "equivalent width",
      "global star formation rate density",
      "average luminosity surface density suffers",
      "absorption"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 16,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}