2002A&A...381...77B

It is clear that outflow activity can have a significant impact on the structure and evolution of material in protostellar environments, but the detailed nature of the interaction between the outflow and surrounding material is not clearly understood. To probe the impact of outflow activity on protostellar core material, in this paper we present observations of CH₃OH (J_k=3_k->2_k), c-C₃H₂ (J_k-_,k+₌₃1,2->2_2,1) and DCN (J=2->1 multiplet) at 145GHz towards a sample of Class 0 and Class I sources, to place constraints on the physical and chemical changes which have taken place through the onset of star formation. CH₃OH was detected towards all of the sources and positions observed. In many sources, the CH₃OH lines have two velocity components: one broad (<Δv≳1.5km/s), and one narrow (<Δv≳0.7km/s). Both velocity components of CH₃OH show significantly (>10) enhanced abundances relative to quiescent dark clouds. These two components are predominantly a feature of the Class 0 sources. These sources also have the broadest lines in both components. c-C₃H₂ was detected towards 87% of the sources observed and DCN was detected towards 66% of the sources observed. The narrowest detected component of c-C₃H₂ has similar linewidths to NH₃, and is detected towards only a small fraction of positions, implying that only a small number of sources contain undisturbed material. The degree of activity implied by the enhanced abundances in CH₃OH is larger in the Class 0 sources than the Class I sources. Since the narrower linewidth components also show enhanced abundances in this molecule, we conclude that energetic activity during the star formation process, which may include both outflow and infall processes, affects the apparently quiescent core material very early in the star formation process.