Knowledge Bank

The formation of CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ in the interstellar medium has been an enigma for the past 70 years. Emission from the species is found in diffuse material, even though the major pathway leading to the species, C$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ + H$2$, is endothermic by 0.40 eV. The barrier for this reaction can be greatly reduced if the H$2$ is vibrationally excited. Using the Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory, we have mapped CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ $(J=1\to 0)$, CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ $(J=2\to 1)$, and C$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ $(J=3/2\to 1/2)$ across the face of the young planetary nebula, NGC 7027. Analysis of the spectra has shown that CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, C$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, and vibrationally excited H$2$ apparently trace the same outflow in NGC 7027. Therefore CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ in this nebula likely forms from the activated C$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ + H$2$ reaction. Spectral maps, temperatures, and abundances of CH$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ will be presented along with spectral maps of C$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$.