Interstellar glycolamide: A comprehensive rotational study and an astronomical search in Sgr B2(N)

Abstract

Context. Glycolamide is a glycine isomer and also one of the simplest derivatives of acetamide (e.g., one hydrogen atom is replaced with a hydroxyl group), which is a known interstellar molecule. Aims. In this context, the aim of our work is to provide direct experimental frequencies of the ground vibrational state of glycolamide in the centimeter-, millimeter- and submillimeter-wavelength regions in order to enable its identification in the interstellar medium. Methods. We employed a battery of state-of-the-art rotational spectroscopic techniques in the frequency and time domain to measure the frequencies of glycolamide. We used the spectral line survey named Exploring Molecular Complexity with ALMA (EMoCA), which was performed toward the star forming region Sgr B2(N) with ALMA to search for glycolamide in space. We also searched for glycolamide toward Sgr B2(N) with the Effelsberg radio telescope. The astronomical spectra were analyzed under the local thermodynamic equilibrium approximation. We used the gas-grain chemical kinetics model MAGICKAL to interpret the results of the astronomical observations. Results. About 1500 transitions have been newly assigned up to 460 GHz to the most stable conformer, and a precise set of spectroscopic constants was determined. Spectral features of glycolamide were then searched for in the prominent hot molecular core Sgr B2(N2). We report the nondetection of glycolamide toward this source with an abundance at least six and five times lower than that of acetamide and glycolaldehyde, respectively. Our astrochemical model suggests that glycolamide may be present in this source at a level just below the upper limit, which was derived from the EMoCA survey. We could also not detect the molecule in the region’s extended molecular envelope, which was probed with the Effelsberg telescope. We find an upper limit to its column density that is similar to the column densities obtained earlier for acetamide and glycolaldehyde with the Green Bank Telescope.