A Search for l-C3H+ and l-C3H in Sgr B2(N), Sgr B2(OH), and the Dark Cloud TMC-1

TL;DR

This study searches for and analyzes specific molecular transitions of l-C3H+ and l-C3H in various interstellar regions, confirming their presence and providing excitation conditions, thus advancing understanding of these molecules in space.

Contribution

It tests previous predictions of l-C3H+ detection by searching for specific transitions in multiple interstellar environments, confirming their presence and characterizing their properties.

Findings

Detected transitions of l-C3H+ in Sgr B2(N), Sgr B2(OH), and TMC-1.

Estimated excitation temperatures and column densities of l-C3H+.

Provided evidence supporting the identification of l-C3H+ in space.

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-C3H+. 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 x 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-C3H+.