Molecular Carbon Chains and Rings in TMC‐1

Abstract

We present mapping results in several rotational transitions of both cyclic and linear HC 3 N, C 6 H, and toward the cyanopolyyne peak of the Ðlamentary dense cloud TMC-1 using the IRAM C 3 H 2 C 3 H, 30 m and MPIfR 100 m telescopes. The spatial distribution of the cumulene carbon chain propadienyli-dene (hereafter is found to deviate signiÐcantly from the distributions of the cyclic H 2 CCC l-C 3 H 2) isomer and which, in turn, look very similar. The cyclic over linear abundance cC 3 H 2 , HC 3 N, C 6 H, ratio of increases by a factor of 3 across the Ðlament, with a value of 28 at the cyanopolyyne peak. C 3 H 2 This abundance ratio is an order of magnitude larger than the range (3È5) we observed in the di †use interstellar medium. The cyclic over linear abundance ratio of also varies by D2.5 in TMC-1, C 3 H reaching a maximum value (13) close to the cyanopolyyne peak. These behaviors might be related to competitive processes between ion-neutral and neutral-neutral reactions for cyclic and linear species.