Comments on some possible models of TMC-1

Chemical differences between cores in the dark ridge TMC-1 have been attributed to the cores being in different stages of chemical evolution with those having high NH3 to cyanopolyyne abundance ratios being the most evolved. We suggest several alternative models including one in which the highest NH3 to cyanopolyyne abundance ratio obtains in the youngest TMC-1 core; in this and in one of the other models the evolution of the chemistry as depletion increases is supposed to lead to a lower NH3 to cyanopolyyne ratio. The possibility that the cyanopolyynes exist primarily in an interface between dark core material and the wind of a low mass star is considered; this wind interface model may account for the sharp cyanopolyyne emission gradient on the side of the ridge away from the star. Implosion of the cores by the ram pressure of the wind may have caused them to collapse more rapidly than gravity could and more rapidly than chemistry evolves so that the chemistry reflects a core's state at a lower density.