2016/05/24 by O. Sipilä, S. Spezzano, P. Caselli · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1051/0004-6361/201628689
published as A&A 591, L1 (2016) · 5 pages, 2 figures; accepted as an A&A Letter
arxiv created 2016/05/24 · arxiv updated 2016/06/08
Aims. We aim to understand the high cyclic-to-linear \rm C3H2 ratio (32 ± 4) observed toward L1544 by Spezzano et al. (2016). Methods. We combine a gas-grain chemical model with a physical model for L1544 to simulate the column densities of cyclic and linear \rm C3H2 observed toward L1544. The most important reactions for the formation and destruction of both forms of \rm C3H2 are identified, and their relative rate coefficients are varied to find the best match to the observations. Results. We find that the ratio of the rate coefficients of \rm C3H3+ + e- \longrightarrow C3H2 + H for cyclic and linear \rm C3H2 must be ∼ 20 in order to reproduce the observations, depending on the branching ratios assumed for the \rm C3H3+ + e- \longrightarrow C3H + H2 reaction. In current astrochemical networks it is assumed that cyclic and linear \rm C3H2 are formed in a 1:1 ratio in the aforementioned reactions. Laboratory studies and/or theoretical calculations are needed to confirm the results of our chemical modeling based on observational constraints.