Knowledge Bank

The Helix Nebula, NGC 7293, has been mapped in HCO$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ J = 1 $\to$ 0 emission with a 70 spatial resolution (1.68 km s$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ velocity resolution) using the Arizona Radio Observatory (ARO) 12 m telescope on Kitt Peak. Over 200 individual positions covering an area of roughly 1000 $\times$ 800 were observed down to a 3$\sigma$ noise level of \textasciitilde 20 mK. HCO$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ was detected at over three-quarters of the positions, with the majority of spectra showing multiple velocity components indicative of a complex kinematic structure. The column density of HCO$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ across the Helix ranges from N $\backslash ~$ 1.4 $\times$ 10$\mathrm{<mrow\; data-mjx-texclass="ORD">11</mrow>}$ to $~{}$2.4 $\times$ 10$\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-2</mrow>}$, with an average N $\backslash ~$ 4 $\times$ 10$\mathrm{<mrow\; data-mjx-texclass="ORD">11</mrow>}$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-2</mrow>}$. The HCO$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ distribution, which traces gas with densities \textasciitilde 10$\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-3</mrow>}$, is similar to that of CO and H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ , with certain point symmetries and red-and blue-shifted regions common in all three molecules; these data are also consistent with observations of atomic lines. The HCO$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ emission appears to trace two ring-like structures emanating from the central star: one is blue-shifted and the other red-shifted with respect to the star, and possibly trace the edges of a bipolar outflow.