3mm-band study of L183 and L1544

The molecular column densities and excitation temperatures derived from these lines were compared to the corresponding parameters in L1544. The data for L1544 were obtained from literature or publicly available surveys, and they were analysed using the same procedure as adopted for L183. An astrochemical model, previously developed for the interpretation of organic molecule emissions towards the methanol peak of L1544, was used to interpret the combined data.

Our analysis reveals clear chemical differences between the two PSCs. While L1544 is richer in carbon-bearing species, in particular carbon chains, oxygen-containing species are generally more abundant in L183. The results are well-reproduced by our chemical model.

The observed chemical differentiation between the two PSCs is caused by the different environmental conditions: the core of L183 is deeply buried in the surrounding cloud, whereas L1544 lies close to the edge of the Taurus Molecular Cloud. The obscuration of L183 from the interstellar radiation field (ISRF) allows the carbon atoms to be locked in carbon monoxide, which ultimately leads to a large abundance of O-bearing species.

In contrast, L1544, being more affected by the ISRF, can keep a fraction of carbon in atomic form, which is needed for the production of carbon chains.