Shocked gas around Cepheus A: evidence for multiple outflows from H2S and SO2 observations |
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Authors: | C Codella R Bachiller M Benedettini P Caselli |
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Affiliation: | Istituto di Radioastronomia, CNR, Sezione di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy;Observatorio Astronómico Nacional (IGN), Apartado 1143, E-28800, Alcaláde Henares, Madrid, Spain;Istituto di Fisica dello Spazio Interplanetario, CNR, Area di Ricerca Tor Vergata, Via Fosso del Cavaliere 100, 00133 Roma, Italy;INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy |
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Abstract: | The Cepheus A star-forming region has been investigated through a multiline H2S and SO2 survey at millimetre wavelengths. Large-scale maps and high-resolution line profiles reveal the occurrence of several outflows. Cep A East is associated with multiple mass-loss processes: in particular, we detect a 0.6-pc jet-like structure which shows for the first time that the Cep A East young stellar objects are driving a collimated outflow moving towards the south. The observed outflows show different clumps associated with definitely different H2S/SO2 integrated emission ratios, indicating that the gas chemistry in Cepheus A has been altered by the passage of shocks. H2S appears to be more abundant than SO2 in high-velocity clumps, in agreement with chemical models. However, we also find quite small H2S linewidths, suggestive of regions where the evaporated H2S molecules had enough time to slow down but not to freeze out on to dust grains. Finally, comparison between the line profiles indicates that the excitation conditions increase with the velocity, as expected for a propagation of collimated bow shocks. |
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Keywords: | ISM: clouds ISM: individual: Cep A ISM: jets and outflows ISM: molecules radio lines: ISM |
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