Laboratory measurements and astronomical search for cyanomethanimine

Abstract

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. 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. 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. 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 $\sim$700 GHz. So far, no C-cyanomethanimine emission has been detected toward the ASAI targets, and upper limits of the column density of $\sim$ 10${}^{11}$--10${}^{12}$ 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, $\le$ 10${}^{-9}$, is obtained for shocks sites. The combination of the upper limits of the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to $\sim$ 700 GHz poses the basis for future higher sensitivity searches around Sun-like-star forming regions.

arXiv comment9 pages, 4 figures, 2 tables. A&A accepted

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• Reexploring Molecular Complexity with ALMA: Insights into chemical differentiation from the molecular composition of hot cores in Sgr B2(N2)
• High-resolution millimeter-wave spectroscopy of CH${}_2$DCl: paving the way for future astronomical observations of chloromethane isotopologues