SIMBAD references

A number of maps of low-mass star-forming regions have shown the molecule CS to be more widespread than NH₃, despite having a higher critical density in the transitions in question. In a previous paper a model was presented of unresolved clumps around the star-forming core. The clumps are transient and exhibit emission only from molecules that form quickly. In this paper it is shown how families of molecules can be found that ought to follow either the CS or NH₃ behaviour if mapped adequately in similar sources. The first family of early-time molecules, includes such species as CH₄, CH₃, H₂CO, H₂CS, HC₃N, CN and HCN. The second family of late-time molecules includes the species HCO⁺, NO, OH, SO, N₂H⁺, O₂, N₂ and OCN. The chemistry of these molecules is discussed.