First detection of CHD2OH towards pre-stellar cores

The inheritance of material across the star and planet formation process is traced by deuterium fractionation. We report here the first detection of doubly deuterated methanol towards pre-stellar cores. We study the deuterium fractionation of methanol, CH3OH, towards two starless and two pre-stellar cores. We derive a D/H ratio of 0.8-1.9% with CH2DOH in pre-stellar cores H-MM1 and L694-2, consistent with measurements in more evolved Class 0/I objects and comet 67P/Churyumov-Gerasimenko, suggesting a direct chemical link arising in the pre-stellar stage. Furthermore, the column density ratios of CHD2OH/CH2DOH are similar to 50-80%, as consistently high as towards Class 0/I objects, indicating an efficient formation mechanism of CHD2OH, possibly through H atom additions to D2CO. The CH2DOH/CH3OH and CHD2OH/CH3OH column density ratios in the two pre-stellar cores are larger than that in the two starless cores B68 and L1521E, representing an evolutionary trend of methanol deuteration in early-stage cores.

Automated summary

The first detection of doubly deuterated methanol in pre-stellar cores is reported, indicating the inheritance of material across the star and planet formation process. The study reveals a D/H ratio of 0.8-1.9% in pre-stellar cores, consistent with measurements in more evolved objects, suggesting a direct chemical link in the pre-stellar stage. The column density ratios of CHD2OH/CH2DOH in the pre-stellar cores indicate an efficient formation mechanism of CHD2OH, while the evolutionary trend of methanol deuteration is observed in early-stage cores.