Seeds of Life in Space (SOLIS)

II. Formamide in protostellar shocks: Evidence for gas-phase formation^⋆

¹ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: codella@arcetri.astro.it
² Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France
³ Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
⁴ Dipartimento di Chimica, Biologia e Biotecnologie, via Elce di Sotto 8, 06123 Perugia, Italy
⁵ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
⁶ Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
⁷ IGN, Observatorio Astronómico Nacional, Calle Alfonso XII, 28004 Madrid, Spain
⁸ Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Italy
⁹ LERMA, Université de Cergy-Pontoise, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC, Univ. Paris 06, 95000 Cergy Pontoise, France
¹⁰ School of Physics and Astronomy Queen Mary, University of London, 327 Mile End Road, E1 4 NS London, UK
¹¹ Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406 Saint-Martin d’ Hères, France
¹² Department of Physics & Astronomy, The University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada
¹³ Université de Rennes 1, Institut de Physique de Rennes, Rennes, France
¹⁴ Ural Federal University, Ekaterinburg, Russia
¹⁵ Université de Toulouse, UPS-OMP, IRAP, Toulouse, France
¹⁶ CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹⁷ University of AL-Muthanna, College of Science, Physics Department, Al-Muthanna, Iraq
¹⁸ Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁹ Dipartimento di Chimica “Giacomo Ciamician”, via F. Selmi, 2, 40126 Bologna, Italy
²⁰ Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
²¹ The Institute of Physical and Chemical Research (RIKEN), 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan
²² Leiden Observatory, Leiden University, 9513, 2300 RA Leiden, The Netherlands
²³ ESO, Karl Schwarzchild Srt. 2, 85478 Garching bei München, Germany
²⁴ Aix-Marseille Université, PIIM UMR-CNRS 7345, 13397 Marseille, France
²⁵ Università degli Studi di Torino, Dipartimento Chimica via Pietro Giuria 7, 10125 Torino, Italy
²⁶ Research Center for the Early Universe, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

Received: 26 May 2017
Accepted: 18 August 2017

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 N_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 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.