{
  "id": "1712.03036",
  "version": "v1",
  "published": "2017-12-08T11:48:18.000Z",
  "updated": "2017-12-08T11:48:18.000Z",
  "title": "First detection of interstellar S2H",
  "authors": [
    "Asunción Fuente",
    "Javier R. Goicoechea",
    "Jerome Pety",
    "Romane Le Gal",
    "Rafael Martín-Doménech",
    "Pierre Gratier",
    "Viviana Guzmán",
    "Evelyne Roueff",
    "Jean Christophe Loison",
    "Guillermo M. Muñoz-Caro",
    "Valentine Wakelam",
    "Maryvonne Gerin",
    "Pablo Riviere-Marichalar",
    "Thomas Vidal"
  ],
  "comment": "8 pages, 2 figures. Astrophysical Journal Letter, in press",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "We present the first detection of gas phase S2H in the Horsehead, a moderately UV-irradiated nebula. This confirms the presence of doubly sulfuretted species in the interstellar medium and opens a new challenge for sulfur chemistry. The observed S2H abundance is ~5x10$^{-11}$, only a factor 4-6 lower than that of the widespread H2S molecule. H2S and S2H are efficiently formed on the UV-irradiated icy grain mantles. We performed ice irradiation experiments to determine the H2S and S2H photodesorption yields. The obtained values are ~1.2x10$^{-3}$ and <1x10$^{-5}$ molecules per incident photon for H2S and S2H, respectively. Our upper limit to the S2H photodesorption yield suggests that photo-desorption is not a competitive mechanism to release the S2H molecules to the gas phase. Other desorption mechanisms such as chemical desorption, cosmic-ray desorption and grain shattering can increase the gaseous S2H abundance to some extent. Alternatively, S2H can be formed via gas phase reactions involving gaseous H2S and the abundant ions S+ and SH+. The detection of S2H in this nebula could be therefore the result of the coexistence of an active grain surface chemistry and gaseous photo-chemistry.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-12-08T11:48:18.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "first detection",
      "interstellar s2h",
      "s2h photodesorption yield",
      "s2h abundance",
      "gas phase reactions"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}