Vol. 640
6. Interstellar and circumstellar matter

First detection of 13CH in the interstellar medium

The CH radical has long been recognized as a reliable proxy of molecular hydrogen in diffuse and translucent clouds. Its rare isotopolog $^{13}$CH, however, had been alluded to as a detection in the interstellar medium. In this paper, Jacob et.al present the detection of $^{13}$CH in absorption toward Sgr B2(M) and other galactic star-forming regions using the upGREAT receiver on board SOFIA. Combining these new data with previous observations of the main CH isotopolog toward the same sight lines, the authors have determined an improved estimate for the 12C^13 ratio as a function of the galactocentric distance.