Laboratory measurements and astronomical search for cyanomethanimine

M. Melosso (1) , A. Melli , C. Puzzarini (1) , C. Codella (2) , L. Spada (3) , L. Dore (1) , C. Degli Esposti (4) , B. Lefloch (2) , R. Bachiller (5) , C. Ceccarelli (6, 2) , J. Cernicharo (7) , V. Barone

1 Dipartimento di Chimica "Giacomo Ciamician"
2 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
3 Edinburgh Napier University
4 Dipartimento di Chimica "G. Ciamician"
5 IGN - Instituto Geografico Nacional
6 INAF - Istituto Nazionale di Astrofisica
7 ICMM - Instituto de Ciencia de Materiales de Madrid

Context. C-cyanomethanimine (HNCHCN), existing in the two Z and E isomeric forms, is a key prebiotic molecule, but, so far, only the E isomer has been detected toward the massive star-forming region Sagittarius B2(N) using transitions in the radio wavelength domain.Aims. With the aim of detecting HNCHCN in Sun-like-star forming regions, the laboratory investigation of its rotational spectrum has been extended to the millimeter-/submillimeter-wave (mm-/submm-) spectral window in which several unbiased spectral surveys have been already carried out.Methods. High-resolution laboratory measurements of the rotational spectrum of C-cyanomethanimine were carried out in the 100–420 GHz range using a frequency-modulation absorption spectrometer. We then searched for the C-cyanomethanimine spectral features in the mm-wave range using the high-sensitivity and unbiased spectral surveys obtained with the IRAM 30-m antenna in the ASAI context, the earliest stages of star formation from starless to evolved Class I objects being sampled.Results. For both the Z and E isomers, the spectroscopic work has led to an improved and extended knowledge of the spectroscopic parameters, thus providing accurate predictions of the rotational signatures up to ~700 GHz. So far, no C-cyanomethanimine emission has been detected toward the ASAI targets, and upper limits of the column density of ~1011–1012 cm-2 could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10-10 for starless and hot-corinos. A less stringent constraint, ≤10-9, is obtained for shocks sites.Conclusions. The combination of the upper limits of the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to ~700 GHz poses the basis for future higher sensitivity searches around Sun-like-star forming regions. For compact (typically less than 1″) and chemically enriched sources such as hot-corinos, the use of interferometers as NOEMA and ALMA in their extended configurations are clearly needed.

Mots clés: ISM: molecules; molecular data; methods: data analysis; methods: laboratory: molecular

Domaines: Astrophysique [astro-ph]

M. Melosso, A. Melli, C. Puzzarini, C. Codella, L. Spada, et al.. Laboratory measurements and astronomical search for cyanomethanimine. Astronomy and Astrophysics - A&A, 2018, 609, pp.A121. ⟨10.1051/0004-6361/201731972⟩. ⟨hal-02968663⟩