Seeds of Life in Space (SOLIS) II. Formamide in protostellar shocks: Evidence for gas-phase formation

Context. Modern versions of the Miller-Urey experiment claim that formamide (NH 2 CHO) 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 NH 2 CHO 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 NH 2 CHO 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 NH 2 CHO = 8 × 10 12 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.

L. Bizzocchi | L. Testi | C. Favre | B. Lefloch | C. Ceccarelli | S. Viti | A. I. Vasyunin | S. Bottinelli | E. Caux | L. Podio | S. Spezzano | R. Neri | P. Ugliengo | J. Pineda | R. Neri | L. Testi | P. Caselli | I. Jim'enez-Serra | L. Bizzocchi | S. Viti | C. Vastel | N. Sakai | E. Caux | C. Ceccarelli | F. Alves | P. Ugliengo | A. Rimola | N. Balucani | I. Sims | B. Lefloch | J. Holdship | C. Puzzarini | F. Vazart | D. Skouteris | C. Kahane | R. Bachiller | F. Fontani | S. Yamamoto | A. Vasyunin | A. L'opez-Sepulcre | C. Codella | A. Pon | P. Caselli | R. Bachiller | C. Codella | L. Wiesenfeld | P. Hily-Blant | A. Coutens | C. Favre | S. Spezzano | J. Laas | Y. Oya | L. Wiesenfeld | C. Vastel | L. Podio | N. Balucani | F. Fontani | S. Bottinelli | V. Baroneinst | S. Feng | E. Bianchi | F. Dulieu | I. Jim'enez-Serra | J. Holdship | J. Pineda | A. Pon | I. Sims | F. Alves | A. Chac'on-Tanarro | R. Choudhury | A. Coutens | P. Hily-Blant | C. Kahane | A. Jaber Al-Edhari | J. Laas | A. L'opez-Sepulcre | J. Ospina | Y. Oya | A. Punanova | C. Puzzarini | D. Quenard | A. Rimola | N. Sakai | D. Skouteris | V. Taquet | P. Theul'e | F. Vazart | S. Yamamoto | F. Dulieu | F. Dulieu | A. López-Sepulcre | V. Taquet | S. Feng | A. Punanova | A. Chac'on-Tanarro | E. Bianchi | D. Quénard | A. J. Al-Edhari | R. Choudhury | J. Ospina | P. Theul'e | V. Baroneinst | P. Caselli | C. Ceccarelli | Jaime E. Pineda | Cristina Puzzarini | Vincenzo Barone | Nadia Balucani | L. Testi | I. Jiménez-Serra | R. Neri | Ian R. Sims | Felipe O. Alves | P. Theulé | Laurent Wiesenfeld | Satoshi Yamamoto | N. Balucani | J. Pineda

[1]  E. Herbst,et al.  Complex Organic Interstellar Molecules , 2009 .

[2]  S. Viti,et al.  The B1 shock in the L1157 outflow as seen at high spatial resolution , 2013, 1309.0433.

[3]  T. Millar,et al.  A Three-Position Spectral Line Survey of Sagittarius B2 between 218 and 263 GHz. I. The Observational Data , 1998 .

[4]  S. Viti,et al.  THE L1157–B1 ASTROCHEMICAL LABORATORY: MEASURING THE TRUE FORMALDEHYDE DEUTERATION ON GRAIN MANTLES , 2014 .

[5]  R. Kaiser,et al.  MECHANISTICAL STUDIES ON THE PRODUCTION OF FORMAMIDE (H2NCHO) WITHIN INTERSTELLAR ICE ANALOGS , 2011 .

[6]  Holger S. P. Müller,et al.  The Cologne Database for Molecular Spectroscopy, CDMS: a useful tool for astronomers and spectroscopists , 2005 .

[7]  Johannes Kästner,et al.  Formation of the prebiotic molecule NH2CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations† †Electronic supplementary information (ESI) available: Geometric details, lists of calculated rate constants. See DOI: 10.1039/c6cp05727f Click here for additional data fi , 2016, Physical chemistry chemical physics : PCCP.

[8]  C. Ceccarelli,et al.  Molecules with a peptide link in protostellar shocks: a comprehensive study of L1157 , 2014, 1408.4857.

[9]  London,et al.  L1157-B1, a factory of complex organic molecules in a solar-type star-forming region , 2017, 1704.04646.

[10]  S. Viti,et al.  The density structure of the L1157 molecular outflow , 2014, 1410.8453.

[11]  J. Brucato,et al.  Synthesis of formamide and isocyanic acid after ion irradiation of frozen gas mixtures , 2016 .

[12]  R. Bachiller,et al.  Chemically active outflow L 1157 , 2001 .

[13]  S. Klippenstein,et al.  Reactions of oxygen atoms with hydrocarbon radicals: a priori kinetic predictions for the CH3 + O, C2H5 + O, and C2H3 + O reactions , 2005 .

[14]  Adwin Boogert,et al.  Observations of the Icy Universe , 2015, 1501.05317.

[15]  R. Saladino,et al.  Genetics first or metabolism first? The formamide clue. , 2012, Chemical Society reviews.

[16]  A. Giorgio,et al.  The CHESS survey of the L1157-B1 shock: the dissociative jet shock as revealed by Herschel–PACS , 2012, 1202.1451.

[17]  A. Tielens,et al.  On the molecular complexity of the hot cores in Orion A - Grain surface chemistry as 'The last refuge of the scoundrel' , 1992 .

[18]  R. Bachiller,et al.  Ammonia emission from bow shocks in the L1157 outflow , 1995 .

[19]  C. Ceccarelli,et al.  Molecular ions in the protostellar shock L1157-B1 , 2014, 1402.2329.

[20]  S. Viti,et al.  Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation , 2014, 1412.8318.

[21]  Bonn,et al.  A precise and accurate determination of the cosmic microwave background temperature at z = 0.89 , 2012, 1212.5456.

[22]  J. Cernicharo,et al.  THE CHESS SURVEY OF THE L1157-B1 SHOCK REGION: CO SPECTRAL SIGNATURES OF JET-DRIVEN BOW SHOCKS , 2012, 1208.4140.

[23]  B. Turner.  A Molecular Line Survey of Sagittarius B2 and Orion--KL from 70 to 115 GHz. II. Analysis of the Data , 1991 .

[24]  R. Garrod,et al.  Complex Chemistry in Star-forming Regions: An Expanded Gas-Grain Warm-up Chemical Model , 2008, 0803.1214.

[25]  V. Barone,et al.  Gas-phase formation of the prebiotic molecule formamide: insights from new quantum computations , 2015, 1507.03741.

[26]  C. Vastel,et al.  Shedding light on the formation of the pre-biotic molecule formamide with ASAI , 2015, 1502.05762.

[27]  Nadia Balucani,et al.  Formation of complex organic molecules in cold objects: the role of gas-phase reactions , 2015, 1501.03668.

[28]  Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores , 2006, astro-ph/0607560.

[29]  P. Hennebelle,et al.  First image of the L1157 molecular jet by the CALYPSO IRAM-PdBI survey , 2016, 1608.05026.

[30]  Johannes Kastner,et al.  Formation of the prebiotic molecule NH$_2$CHO on astronomical amorphous solid water surfaces: accurate tunneling rate calculations , 2016 .

[31]  Astronomy,et al.  The CHESS survey of the L1157-B1 bow-shock: high and low excitation water vapor , 2013, 1311.2840.

[32]  E. Herbst,et al.  REACTIVE DESORPTION AND RADIATIVE ASSOCIATION AS POSSIBLE DRIVERS OF COMPLEX MOLECULE FORMATION IN THE COLD INTERSTELLAR MEDIUM , 2013, 1303.7266.

[33]  The gas-phase chemistry of carbon chains in dark cloud chemical models , 2013, 1311.3865.

[34]  F. Duvernay,et al.  Hydrogenation at low temperatures does not always lead to saturation: the case of HNCO , 2015, 1502.03282.

[35]  P. Caselli,et al.  Formation of Complex Molecules in Prestellar Cores: A Multilayer Approach , 2017, 1705.04747.

[36]  J. Jørgensen,et al.  Complex Molecules in the L1157 Molecular Outflow , 2008, 0805.2550.

[37]  Cecilia Ceccarelli,et al.  Our astrochemical heritage , 2012, 1210.6368.

[38]  C. Ceccarelli,et al.  DETECTION OF FORMAMIDE, THE SIMPLEST BUT CRUCIAL AMIDE, IN A SOLAR-TYPE PROTOSTAR , 2013 .

[39]  L. Ziurys,et al.  FORMATION OF PEPTIDE BONDS IN SPACE: A COMPREHENSIVE STUDY OF FORMAMIDE AND ACETAMIDE IN Sgr B2(N) , 2011 .