{
  "id": "1703.02053",
  "version": "v1",
  "published": "2017-03-06T19:00:05.000Z",
  "updated": "2017-03-06T19:00:05.000Z",
  "title": "Galaxy Zoo: star-formation versus spiral arm number",
  "authors": [
    "Ross E. Hart",
    "Steven P. Bamford",
    "Kevin R. V Casteels",
    "Sandor J. Kruk",
    "Chris J. Lintott",
    "Karen L. Masters"
  ],
  "comment": "15 pages, 13 figures, accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Spiral arms are common features in low-redshift disc galaxies, and are prominent sites of star-formation and dust obscuration. However, spiral structure can take many forms: from galaxies displaying two strong `grand design' arms, to those with many `flocculent' arms. We investigate how these different arm types are related to a galaxy's star-formation and gas properties by making use of visual spiral arm number measurements from Galaxy Zoo 2. We combine UV and mid-IR photometry from GALEX and WISE to measure the rates and relative fractions of obscured and unobscured star formation in a sample of low-redshift SDSS spirals. Total star formation rate has little dependence on spiral arm multiplicity, but two-armed spirals convert their gas to stars more efficiently. We find significant differences in the fraction of obscured star-formation: an additional $\\sim 10$ per cent of star-formation in two-armed galaxies is identified via mid-IR dust emission, compared to that in many-armed galaxies. The latter are also significantly offset below the IRX-$\\beta$ relation for low-redshift star-forming galaxies. We present several explanations for these differences versus arm number: variations in the spatial distribution, sizes or clearing timescales of star-forming regions (i.e., molecular clouds), or contrasting recent star-formation histories.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-03-06T19:00:05.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galaxy zoo",
      "star-formation",
      "visual spiral arm number measurements",
      "total star formation rate",
      "mid-ir dust emission"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}