tutelles et partenaires


Accueil > Résultats Scientifiques > Publications 2017

First detection of interstellar S2H

par webmaster - publié le

Authors : Fuente, Asunción ; Goicoechea, Javier R. ; Pety, Jerome ; Le Gal, Romane ; Martín-Doménech, Rafael ; Gratier, Pierre ; Guzmán, Viviana ; Roueff, Evelyne ; Loison, Jean Christophe ; Muñoz-Caro, Guillermo M. ; Wakelam, Valentine ; Gerin, Maryvonne ; Riviere-Marichalar, Pablo ; Vidal,Thomas.
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.
Journal : Astrophysical Journal Letter ArXiv