2017/08/15 by C. Codella, C. Ceccarelli, P. Caselli +47 · 2 citations
Physics and Astronomy · #astro-ph.EP
paper · pdf · doi:10.1051/0004-6361/201731249
7 pages, 1 table, 5 figures, A&A Letters, in press
arxiv created 2017/08/15 · arxiv updated 2017/09/13
Context: Modern versions of the Miller-Urey experiment claim that formamide (NH2CHO) could be the starting point for the formation of metabolic and genetic macromolecules. Intriguingly, formamide is indeed observed in regions forming Solar-type stars as well as in external galaxies. Aims: How NH2CHO is formed has been a puzzle for decades: our goal is to contribute to the hotly debated question of whether formamide is mostly formed via gas-phase or grain surface chemistry. Methods: We used the NOEMA interferometer to image NH2CHO towards the L1157-B1 blue-shifted shock, a well known interstellar laboratory, to study how the components of dust mantles and cores released into the gas phase triggers the formation of formamide. Results: We report the first spatially resolved image (size ∼ 9", ∼ 2300 AU) of formamide emission in a shocked region around a Sun-like protostar: the line profiles are blueshifted and have a FWHM ≃ 5 km s-1. A column density of N\rm NH2CHO = 8 × 1012 cm-1, and an abundance (with respect to H-nuclei) of 4 × 10-9 are derived. We show a spatial segregation of formamide with respect to other organic species. Our observations, coupled with a chemical modelling analysis, indicate that the formamide observed in L1157-B1 is formed by gas-phase chemical process, and not on grain surfaces as previously suggested. Conclusions: The SOLIS interferometric observations of formamide provide direct evidence that this potentially crucial brick of life is efficiently formed in the gas-phase around Sun-like protostars.