Seeds of Life in Space (SOLIS). II. Formamide in protostellar shocks: Evidence for gas-phase formation
Abstract
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 and 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 NOrthern Extended Millimeter Array (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 NNH2CHO = 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 a gas-phase chemical process and not on grain surfaces as previously suggested.
Conclusions: The Seeds of Life in Space (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.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- September 2017
- DOI:
- 10.1051/0004-6361/201731249
- arXiv:
- arXiv:1708.04663
- Bibcode:
- 2017A&A...605L...3C
- Keywords:
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- stars: formation;
- ISM: jets and outflows;
- ISM: molecules;
- ISM: individual objects: L1157-B1;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 7 pages, 1 table, 5 figures, A&