First Detection of the Glycine Isomer Glycolamide in Hot Molecular Core

Abstract

Understanding whether prebiotic molecules can endure and reform through the energetic stages of star formation is essential for tracing the continuity of interstellar chemistry toward life. Glycolamide, an isomer of glycine, was recently detected in the molecular cloud G+0.693-0.027. However, establishing its presence in warm, high-density environments is crucial to evaluate the chemical continuity of amides. Here we report the first detection of glycolamide in a hot molecular core, G358.93-0.03 MM1, using ALMA 1 mm observations. Seven unblended or only mildly blended emission lines were identified, yielding an abundance of (1.7$\pm$0.2)$\times 10^{-10}$ relative to H$_{2}$. The comparable formamide/glycolamide and acetamide/glycolamide abundance ratios in both sources suggest a chemically connected amide network across different environments. These results demonstrate that amides can persist and chemically evolve during massive star formation, tracing the chemical continuity from interstellar to protostellar environments.

Figures (4)

• Figure 1: (a) 1 mm continuum image of G358.93-0.03. Contour levels correspond to (20, 40, 80, 120, 200, 500, 1000, 1700) $\times$$\sigma$, where $\sigma$ is the rms noise level. The white ellipse in the lower-left corner indicates the synthesized beam 0.15$^{\prime \prime}$×0.1$^{\prime \prime}$ (position angle -87.1$^\circ$). (b) Enlarged view of MM1. The continuum peak is marked by a white cross, and the offset extraction position used for spectral analysis is marked by a red cross. (c-e) Integrated intensity (Moment-0) maps of NH$_{2}$CHO, CH$_{3}$C(O)NH$_{2}$, and $syn$-HOCH$_{2}$C(O)NH$_{2}$ toward G358.93 MM1, overlaid with 1 mm continuum emission contours from panel (a). The color scale unit is Jy beam$^{-1}$ km s$^{-1}$.
• Figure 2: Unblended or only slightly blended emission lines (red asterisks) of $syn$-HOCH$_{2}$C(O)NH$_{2}$ toward G358.93 MM1. Black lines show the observed spectra, while red lines represent the LTE model of $syn$-HOCH$_{2}$C(O)NH$_{2}$. Blue lines correspond to composite model including contributions from all other identified molecular species. Green dashed lines mark the 3$\sigma$ noise level. The upper energy level energies ($E_{\rm u}$) of the transitions are given above each panel.
• Figure 3: Observed (gray) and best-fit LTE-modeled (red) spectra of NH$_{2}$CHO, NH$_{2}$$^{13}$CHO, and CH$_{3}$C(O)NH$_{2}$ toward G358.93 MM1. All other plotting conventions are the same as in Fig. \ref{['fig:2']}.
• Figure 4: (a) Abundances of FA, AA, and GA relative to H$_{2}$ in G358.93 MM1, compared with other sources and model predictions. Model labels: (1-3) = Fast/Medium/Slow warm-up models from Garrod et al. 2022ApJS..259....1G; and (4) = the model of Sanz et al. 2020ApJ...899...65S. (b)-(d) Abundance ratios FA/AA, AA/GA, and FA/GA. Arrows denote lower limits. The cyan shaded regions indicate the uncertainty ranges (one order of magnitude) for the ratios derived in this work.