A Search for l-C_3H^+ and l-C_3H in Sgr B2(N), Sgr B2(OH), and the Dark Cloud TMC-1

Abstract

Pety et al. (2012) recently reported the detection of several transitions of an unknown carrier in the Horsehead PDR and attribute them to l-C_3H^+. Here, we have tested the predictive power of their fit by searching for, and identifying, the previously unobserved J = 1−0 and J = 2−1 transitions of the unknown carrier (B11244) towards Sgr B2(N) in data from the publicly available PRIMOS project. Also presented here are observations of the J = 6 − 5 and J = 7 − 6 transitions towards Sgr B2(N) and Sgr B2(OH) using the Barry E. Turner Legacy Survey and results from the Kaifu et al. (2004) survey of TMC-1. We calculate an excitation temperature and column density of B11244 of ∼10 K and ∼10^(13) cm^(−2) in Sgr B2(N) and ∼79 K with an upper limit of ≤ 1.5 × 10^(13) cm^(−2) in Sgr B2(OH) and find trace evidence for the cation's presence in TMC-1. Finally, we present spectra of the neutral species in both Sgr B2(N) and TMC-1, and comment on the robustness of the assignment of the detected signals to l-C_3H^+.

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