<i>Herschel</i>observations of EXtra-Ordinary Sources (HEXOS): detecting spiral arm clouds by CH absorption lines
<i>Herschel</i>observations of EXtra-Ordinary Sources (HEXOS): detecting spiral arm clouds by CH absorption lines
We have observed CH absorption lines ($J=3/2, N=1 \leftarrow J=1/2, N=1$) against the continuum source Sgr~B2(M) using the \textit{Herschel}/HIFI instrument. With the high spectral resolution and wide velocity coverage provided by HIFI, 31 CH absorption features with different radial velocities and line widths are detected and identified. The narrower line …