Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation

摘要: The formation of complex organic molecules (COMs) in protostellar environments is a hotly debated topic. In particular, the relative importance gas phase processes as compared to direct COMs on dust grain surfaces so far unknown. We report here first high-resolution images acetaldehyde (CH$_3$CHO) emission towards chemically rich shock L1157-B1, obtained at 2 mm with IRAM Plateau de Bure interferometer. Six blueshifted CH$_3$CHO lines $E_{\rm u}$ = 26-35 K have been detected. spatial distribution follows young ($\sim$ 2000 yr) outflow cavity produced by impact jet ambient medium, indicating that this COM closely associated region enriched iced species evaporated from mantles and released into phase. A high abundance, 2-3 $\times$ 10$^{-8}$, inferred, similarly what found hot-corinos. Astrochemical modelling indicates reactions can produce observed quantity only if large fraction carbon, order 0.1%, locked hydrocarbons.