HEILES CLOUD-2 AND TMC-1 - A CHEMICAL REINTERPRETATION

Norman & Silk have argued that gas in regions of low-mass star formation passes through dynamical cycles of collapse, fragmentation, and finally dissipation by the winds of young stars. Such cycles occur many times during the lifetimes of these regions. B5 is the only such region for which observational results have been presented in the context of this picture and for which theoretical chemical models based on such a dynamical picture have been developed. The possibility of dynamical cycling in regions such as Heiles Cloud 2 and L134N has not been considered; specifically, the chemical models of TMC-1 in Heiles Cloud 2 have been constructed under the assumption that it is a quiescent clump, a view engendered, in part, by the way in which observations of it were initially discussed. We stress that other low-mass star forming regions are probably suitably described by the dynamical and chemical models presented for B5. Distinct chemical signatures of the cyclic models exist, and the adoption of the dynamical-chemical model which we advocate suggests specific observing strategies, such as mapping C I, C II, and CH emission in the vicinity of fragment interfaces, that should be implemented for Heiles Cloud 2 and other low-mass star forming regions.