Interstellar detection of the simplest aminocarbyne, H2NC: an ignored but abundant molecule

Abstract

We report the first identification in space of H2NC, a high-energy isomer of H2CN that has been largely ignored in chemical and astrochemical studies. The observation of various unidentified lines around 72.2 GHz in the cold dark cloud L483 motivated the search for, and successful detection of, additional groups of lines in harmonic relation. After an exhaustive high-level ab initio screening of possible carriers, we confidently assign the unidentified lines to H2NC based on the good agreement between astronomical and theoretical spectroscopic parameters and sound spectroscopic and astrochemical arguments. The observed frequencies are used to precisely characterize the rotational spectrum of H2NC. This species is also detected in the cold dark cloud B1-b and the z=0.89 galaxy in front of the quasar PKS1830-211. We derive H2NC/H2CN abundance ratios of 1 in L483 and B1-b and 0.27 toward PKS1830-211. Neither H2NC nor H2CN are detected in the dark cloud TMC-1, which seriously questions a previous identification of H2CN in this source. We suggest that the H2NC/H2CN ratio behaves as the HNC/HCN ratio, with values close to one in cold dense clouds and below one in diffuse clouds. The reactions N + CH3 and C + NH3 emerge as strong candidates to produce H2NC in interstellar clouds. Further studies on these two reactions are needed to evaluate the yield of H2NC. Due to the small number of atoms involved, it should be feasible to constrain the chemistry behind H2NC and H2CN, just as it has been done for HNC and HCN, as this could allow to use the H2NC/H2CN ratio as a probe of chemical or physical conditions of the host clouds.

Accepted for publication in A&A

References in corpus (9)

• The 2014 KIDA network for interstellar chemistry
• Detection of C5N- and vibrationally excited C6H in IRC +10216
• Probing isotopic ratios at z = 0.89: molecular line absorption in front of the quasar PKS 1830-211
• Isocyanogen formation in the cold interstellar medium
• Space and laboratory observation of the deuterated cyanomethyl radical HDCCN
• An unbiased spectral line survey observation toward the low-mass star-forming region L1527
• New molecular species at redshift z=0.89
• A sensitive 3 mm line survey of L483: a broad view of the chemical composition of a core around a Class 0 object
• First detection of doubly deuterated methyl acetylene (CHD2CCH and CH2DCCD)

Cited by in corpus (14)

• Discovery of the elusive thioketenylium, HCCS+, in TMC-1
• First detection in space of the high-energy isomer of cyanomethanimine: H2CNCN
• Discovery of C5H+ and detection of C3H+ in TMC-1 with the QUIJOTE line survey
• The abundance and excitation of molecular anions in interstellar clouds
• Discovery of a new molecular ion, HC7NH+, in TMC-1
• Discovery of interstellar NC4NH+: dicyanopolyynes are indeed abundant in space
• Similar levels of deuteration in the pre-stellar core L1544 and the protostellar core HH211
• New deuterated species in TMC-1: Detection of CH2DC4H with the QUIJOTE line survey
• The chemistry of H2NC in the interstellar medium and the role of the C + NH3 reaction
• H2CN/H2NC abundance ratio: a new potential temperature tracer for the interstellar medium
• Laboratory observation and astronomical search of 1-cyano propargyl radical, HCCCHCN
• Piecing together formic acid isomerism in dark clouds. Detection of cis-formic acid in TMC-1 and astrochemical modeling
• Post-Outburst Chemistry in a Very Low-Luminosity Object: Peculiar High Abundance of Nitric Oxide
• Rotational Spectra and Search for Aromatic Imines: 9-Iminofluorene and Benzophenone imine