Open AccessShocked gas around Cepheus A: evidence for multiple outflows from H 2 S and SO 2 observations
Author(s) -
Codella C.,
Bachiller R.,
Benedettini M.,
Caselli P.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06444.x
Subject(s) - physics , astrophysics , outflow , collimated light , jet (fluid) , wavelength , star formation , astronomy , high resolution , stars , optics , remote sensing , meteorology , laser , thermodynamics , geology
The Cepheus A star‐forming region has been investigated through a multiline H 2 S and SO 2 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 H 2 S/SO 2 integrated emission ratios, indicating that the gas chemistry in Cepheus A has been altered by the passage of shocks. H 2 S appears to be more abundant than SO 2 in high‐velocity clumps, in agreement with chemical models. However, we also find quite small H 2 S linewidths, suggestive of regions where the evaporated H 2 S 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.