First detection of cyanamide (NH₂CN) towards solar-type protostars

¹ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
e-mail: audrey.coutens@u-bordeaux.fr
² Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904, USA
³ I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
⁴ SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK
⁵ Centre for Star and Planet Formation, Niels Bohr Institute and Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark
⁶ Center for Space and Habitability, Universität Bern, Sidlerstr. 5, 3012 Bern, Switzerland
⁷ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁸ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁹ ASTRON Netherlands Institute for Radio Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
¹⁰ Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748 Garching, Germany

Received: 22 November 2017
Accepted: 26 December 2017

Abstract

Searches for the prebiotically relevant cyanamide (NH₂CN) towards solar-type protostars have not been reported in the literature. We present here the first detection of this species in the warm gas surrounding two solar-type protostars, using data from the Atacama Large Millimeter/Submillimeter Array Protostellar Interferometric Line Survey (PILS) of IRAS 16293–2422 B and observations from the IRAM Plateau de Bure Interferometer of NGC 1333 IRAS2A. We also detected the deuterated and ¹³C isotopologs of NH₂CN towards IRAS 16293–2422 B. This is the first detection of NHDCN in the interstellar medium. Based on a local thermodynamic equilibrium analysis, we find that the deuteration of cyanamide (~1.7%) is similar to that of formamide (NH₂CHO), which may suggest that these two molecules share NH₂ as a common precursor. The NH₂CN/NH₂CHO abundance ratio is about 0.2 for IRAS 16293–2422 B and 0.02 for IRAS2A, which is comparable to the range of values found for Sgr B2. We explored the possible formation of NH₂CN on grains through the NH₂ + CN reaction using the chemical model MAGICKAL. Grain-surface chemistry appears capable of reproducing the gas-phase abundance of NH₂CN with the correct choice of physical parameters.