Journal or Book Title
Astronomy and Astrophysics
We report the first detection of the ground-state rotational transition of the methylidyne cation CH+ towards the massive star-forming region DR 21 with the HIFI instrument onboard the Herschel satellite. The line profile exhibits a broad emission line, in addition to two deep and broad absorption features associated with the DR 21 molecular ridge and foreground gas. These observations allow us to determine a 12CH+J = 1–0 line frequency of ν = 835 137 ± 3 MHz, in good agreement with a recent experimental determination. We estimate the CH+ column density to be a few 1013 cm-2 in the gas seen in emission, and >1014 cm-2 in the components responsible for the absorption, which is indicative of a high line of sight average abundance [CH+] /[H] > 1.2 × 10-8. We show that the CH+ column densities agree well with the predictions of state-of-the-art C-shock models in dense UV-illuminated gas for the emission line, and with those of turbulent dissipation models in diffuse gas for the absorption lines.
Falgarone, E; Ossenkopf, V; Gerin, M; Lesaffre, P; Godard, B; Pearson, J; Cabrit, S; Joblin, Ch; Benz, AO; Boulanger, F; Fuente, A; Gusten, R; Harris, A; Klein, T; Kramer, C; Lord, S; Martain, P; Martin-Pintado, J; Neufeld, D; Phillips, TG; Rollig, M; Simon, R; Stutzki, J; van der Tak, F; Teyssier, D; Yorke, H; Erickson, NR; Fich, M; Jellema, W; Marston, A; Risacher, C; Salez, M; and Schmulling, F, "Strong CH+ J = 1–0 emission and absorption in DR21*" (2010). Astronomy and Astrophysics. 1159.