First detection of ethylene oxide and acetaldehyde in hot core G358.93–0.03 MM1: Tracing prebiotic oxygen chemistry

Abstract

Ethylene oxide (c- [Figure presented] ) and its isomer, acetaldehyde (CH3CHO), are important complex organic molecules owing to their potential role in the formation of amino acids (R–CH(NH2)-COOH) in interstellar medium. The detection of c- [Figure presented] in hot molecular cores suggests the possible existence of larger ring-shaped molecules containing more than three carbon atoms, such as furan (c- [Figure presented] ), which shares structural similarities with ribose (C5H10O5), the sugar component of DNA. In this study, we report the first detection of the rotational emission lines of c- [Figure presented] and CH3CHO towards the hot molecular core G358.93–0.03 MM1, based on observations from the Atacama Large Millimeter/Submillimeter Array (ALMA) in band 7. The fractional abundances of c- [Figure presented] and CH3CHO relative to H2 are (2.1±0.2)×10−9 and (7.1±0.9)×10−9, respectively. The column density ratio between CH3CHO and c- [Figure presented] is 3.4±0.7. A Pearson correlation heat map reveals strong positive correlations (r > 0.5) between the abundances and excitation temperatures of c- [Figure presented] and CH3CHO, suggesting a possible chemical connection between those two molecules. To investigate this further, we conducted a two-phase warm-up chemical model using the gas-grain chemical code UCLCHEM. A comparison between our derived abundances and the predictions from our chemical model and existence model demonstrates good agreement within factors of 0.73 and 0.74, respectively. We propose that c- [Figure presented] may form in G358.93–0.03 MM1 via the grain surface reaction between C2H4 and O, but CH3CHO may be produced through the surface reaction between CH3 and HCO.