The interaction between protostars and their environment: Carbon-bearing species towards low mass protostars

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+) = 3(1,2) --> 2(2,1)) and DCN (J = 2 -->1 multiplet) at 145 GHz 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 ([Deltav] similar to 1.5 km s(-1)), and one narrow ([Deltav] similar to 0.7 km s(-1)). 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 out ow and infall processes, affects the apparently quiescent core material very early in the star formation process.