{
  "id": "2002.05744",
  "version": "v1",
  "published": "2020-02-13T19:08:39.000Z",
  "updated": "2020-02-13T19:08:39.000Z",
  "title": "SDSS IV MaNGA -- Metallicity and ionisation parameter in local star-forming galaxies from Bayesian fitting to photoionisation models",
  "authors": [
    "M. Mingozzi",
    "F. Belfiore",
    "G. Cresci",
    "K. Bundy",
    "M. Bershady",
    "D. Bizyaev",
    "G. Blanc",
    "M. Boquien",
    "N. Drory",
    "H. Fu",
    "R. Maiolino",
    "R. Riffel",
    "A. Schaefer",
    "T. Storchi-Bergmann",
    "E. Telles",
    "C. Tremonti",
    "N. Zakamska",
    "K. Zhang"
  ],
  "comment": "27 pages, 23 figures, resubmitted to A&A",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We measured gas-phase metallicity, ionisation parameter and dust extinction for 1795 representative local star-forming galaxies using integral field spectroscopy from the SDSS-IV MaNGA survey. We self-consistently derive these quantities by comparing observed line fluxes with photoionisation models using a Bayesian framework. We also present the first comprehensive study of the [SIII]$\\lambda\\lambda$9069,9532 nebular lines, which have long been predicted to be ideal tracers of the ionisation parameter. Unfortunately, we find that current photoionisation models substantially over-predict [SIII] lines intensity, while broadly reproducing other observed optical line ratios. We discuss how to nonetheless make use of the information provided by [SIII] lines by setting a prior on the ionisation parameter. Following this approach, we derive spatially-resolved maps and radial profiles of metallicity and ionisation parameter. The metallicity radial profiles are comparable with previous works, with metallicity declining toward the outer parts and a flattening in the central regions, in agreement with infall models of galaxy formation, that predict that spiral discs build up through accretion of material, which leads to an inside-out growth. On the other hand, ionisation parameter radial profiles are flat for low-mass galaxies, while their slope becomes positive as galaxy mass increases. However, the ionisation parameter maps we obtain are clumpy, especially for low-mass galaxies. Ionisation parameter is tightly correlated with the H$\\alpha$ equivalent width [EW(H$\\alpha$)], following a nearly universal relation, which we attribute to the change of the spectral shape of ionising sources due to ageing of HII regions. We derive a positive correlation between ionisation parameter and metallicity at fixed EW(H$\\alpha$), in disagreement with previous theoretical works expecting an anti-correlation.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-02-13T19:08:39.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "local star-forming galaxies",
      "metallicity",
      "bayesian fitting",
      "ionisation parameter radial profiles",
      "low-mass galaxies"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 27,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}