We present the first detection of (Z)-1,2-ethenediol, (CHOH)₂, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693−0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 ± 0.1) × 10¹³ cm⁻², which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10⁻¹⁰. The abundance ratio between glycolaldehyde and (Z)-1,2-ethenediol is ∼5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H₂CO, CHOH, or CH₂CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH₂CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.

Context.Peptide-like bond molecules, which can take part in the formation of proteins in a primitive Earth environment, have been detected only towards a few hot cores and hot corinos up to now.Aims.We present a study of HNCO, HC(O)NH₂, CH₃NCO, CH₃C(O)NH₂, CH₃NHCHO, CH₃CH₂NCO, NH₂C(O)NH₂, NH₂C(O)CN, and HOCH₂C(O)NH₂towards the hot core G31.41+0.31. The aim of this work is to study these species together to allow a consistent study among them.Methods.We have used the spectrum obtained from the ALMA 3 mm spectral survey GUAPOS, with a spectral resolution of ~0.488 MHz (~1.3–1.7 km s⁻¹) and an angular resolution of 1.′′2 × 1.′′2 (~4500 au), to derive column densities of all the molecular species presented in this work, together with 0.′′2 × 0.′′2 (~750 au) ALMA observations from another project to study the morphology of HNCO, HC(O)NH₂, and CH₃C(O)NH₂.Results.We have detected HNCO, HC(O)NH₂, CH₃NCO, CH₃C(O)NH₂, and CH₃NHCHO, but no CH₃CH₂NCO, NH₂C(O)NH₂, NH₂C(O)CN, or HOCH₂C(O)NH₂. This is the first time that these molecules have been detected all together outside the Galactic centre. We have obtained molecular fractional abundances with respect to H₂from 10⁻⁷down to a few 10⁻⁹and abundances with respect to CH₃OH from 10⁻³to ~4 × 10⁻², and their emission is found to be compact (~2′′, i.e. ~7500 au). From the comparison with other sources, we find that regions in an earlier stage of evolution, such as pre-stellar cores, show abundances at least two orders of magnitude lower than those in hot cores, hot corinos, or shocked regions. Moreover, molecular abundance ratios towards different sources are found to be consistent between them within ~1 order of magnitude, regardless of the physical properties (e.g. different masses and luminosities), or the source position throughout the Galaxy. Correlations have also been found between HNCO and HC(O)NH₂as well as CH₃NCO and HNCO abundances, and for the first time between CH₃NCO and HC(O)NH₂, CH₃C(O)NH₂and HNCO, and CH₃C(O)NH₂and HC(O)NH₂abundances. These results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas phase through thermal desorption or shock-triggered desorption.

Ethanimine, a possible precursor of amino acids, is considered an important prebiotic molecule and thus may play important roles in the formation of biological building blocks in the interstellar medium. In addition, its identification in Titan’s atmosphere would be important for understanding the abiotic synthesis of organic species. An accurate computational characterization of the molecular structure, energetics, and spectroscopic properties of the E and Z isomers of ethanimine, CH₃CHNH, has been carried out by means of a composite scheme based on coupled-cluster techniques, which also account for extrapolation to the complete basis-set limit and core-valence correlation correction, combined with density functional theory for the treatment of vibrational anharmonic effects. By combining the computational results with new millimeter-wave measurements up to 300 GHz, the rotational spectrum of both isomers can be accurately predicted up to 500 GHz. Furthermore, our computations allowed us to revise the infrared spectrum of both E- and Z-CH₃CHNH, thus predicting all fundamental bands with high accuracy.

Context. Aminoacetonitrile, a molecule detected in the interstellar medium only toward the star-forming region Sagittarius B2 (Sgr B2), is considered an important prebiotic species; in particular, it is a possible precursor of the simplest amino acid glycine. To date, observations have been limited to ground state emission lines, whereas transitions from within vibrationally excited states remained undetected. Aims. We wanted to accurately determine the energies of the low-lying vibrational states of aminoacetonitrile, which are expected to be populated in Sgr B2(N1), the main hot core of Sgr B2(N). This step is fundamental in order to properly evaluate the vibration-rotation partition function of aminoacetonitrile as well as the line strengths of the rotational transitions of its vibrationally excited states. This is necessary to derive accurate column densities and secure the identification of these transitions in astronomical spectra. Methods. The far-infrared ro-vibrational spectrum of aminoacetonitrile has been recorded in absorption against a synchrotron source of continuum emission. Three bands, corresponding to the lowest vibrational modes of aminoacetonitrile, were observed in the frequency region below 500 cm⁻¹. The combined analysis of ro-vibrational and pure rotational data allowed us to prepare new spectral line catalogs for all the states under investigation. We used the imaging spectral line survey ReMoCA performed with ALMA to search for vibrationally excited aminoacetonitrile toward Sgr B2(N1). The astronomical spectra were analyzed under the local thermodynamic equilibrium (LTE) approximation. Results. Almost 11 000 lines have been assigned during the analysis of the laboratory spectrum of aminoacetonitrile, thanks to which the vibrational energies of the v₁₁ = 1, v₁₈ = 1, and v₁₇ = 1 states have been determined. The whole dataset, which includes high J and K_a transitions, is well reproduced within the experimental accuracy. Reliable spectral predictions of pure rotational lines can now be produced up to the THz region. On the basis of these spectroscopic predictions, we report the interstellar detection of aminoacetonitrile in its v₁₁ = 1 and v₁₈ = 1 vibrational states toward Sgr B2(N1) in addition to emission from its vibrational ground state. The intensities of the identified v₁₁ = 1 and v₁₈ = 1 lines are consistent with the detected v = 0 lines under LTE at a temperature of 200 K for an aminoacetonitrile column density of 1.1 × 10¹⁷ cm⁻². Conclusions. This work shows the strong interplay between laboratory spectroscopy exploiting (sub)millimeter and synchrotron-based far-infrared techniques, and observational spectral surveys to detect complex organic molecules in space and quantify their abundances.

Context.C-cyanomethanimine (HNCHCN), existing in the twoZandEisomeric forms, is a key prebiotic molecule, but, so far, only theEisomer 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 theZandEisomers, 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 ~10¹¹–10¹²cm^-2could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10^-10for 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.