Detection of antifreeze molecule ethylene glycol in the hot molecular core G358.93$-$0.03 MM1

The identification of complex prebiotic molecules using millimeter and submillimeter telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium (ISM), ethylene glycol ((CH₂OH)₂) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (CH₂OHCHO). We present the first detection of the rotational emission lines of aGg^ conformer of ethylene glycol ((CH₂OH)₂) towards the hot molecular core G358.93$-$0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The estimated column density of aGg^-(CH₂OH)₂ towards the G358.93$-$0.03 MM1 is (4.5±0.1)×10¹⁶ cm⁻² with an excitation temperature of 155±35 K. The abundance of aGg^-(CH₂OH)₂ with respect to H₂ is (1.4±0.5)×10⁻⁸. Similarly, the abundances of aGg^-(CH₂OH)₂ with respect to CH₂OHCHO and CH₃OH are 3.1±0.5 and (6.1±0.3)×10⁻³. We compare the estimated abundance of aGg^-(CH₂OH)₂ with the existing three-phase warm-up chemical model abundance of (CH₂OH)₂, and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of aGg^-(CH₂OH)₂ towards the hot molecular cores, and we find that aGg^-(CH₂OH)₂ is probably created via the recombination of two CH₂OH radicals on the grain surface of G358.93$-$0.03 MM1.