Observations of the cyclic C3H radical in the interstellar medium.

We report the results from a survey of cyclopropynylidyne (cyclic C3H, hereafter denoted as c-C3H), previously detected only in TMC-1, towards several Galactic molecular clouds. c-C3H has been detected in 13 of the 19 sources observed. Comparison between c-C3H and the only other hydrocarbon ring molecule discovered in the interstellar medium, C3H2, reveals that N_TOT(c-C3H)=(9.04±2.87)×10^-2 N_TOT(C3H2). We also find that the warmer sources in our survey show no systematic differences in N_TOT(c-C3H)/N_TOT(C3H2) when compared to their cold cloud counterparts. This observed abundance correlation between c-C3H and C3H2 suggests that these two hydrocarbon ring molecules have a common precursor, C3H3+.