Linelists for C3H- from CALPGM

Recent high-level ab initio calculations have called this assignment into question; the anionic C_3_H^-^ molecule has been suggested as a more likely candidate. Here, we examine observations of the Horsehead PDR, Sgr B2(N), TMC-1, and IRC+10216 in the context of both l-C_3_H^+^ and C_3_H^-^.

We find no observational evidence of K_a_=1 lines, which should be present were the carrier indeed C_3_H^-^. Additionally, we find a strong anticorrelation between the presence of known molecular anions and B11244 in these regions. Finally, we discuss the formation and destruction chemistry of C_3_H^-^ in the context of the physical conditions in the regions.