ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – XXI. A large-sample observational study of ethanol and dimethyl ether in hot cores

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Hot cores, as a stage of massive star formation, exhibit abundant line emissions of complex organic molecules (COMs). We present a deep line survey of two isomers of C₂H₆O: ethanol (C₂H₅OH; EA), and dimethyl ether (CH₃OCH₃; DE) as well as their possible precursor CH₃OH towards 60 hot cores by using the Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm line observations. EA is detected in 40 hot cores and DE is detected in 59 hot cores. Of these, EA and DE are simultaneously detected in 39 hot cores. We calculate rotation temperatures and column densities of EA and DE by using the eXtended CASA Line Analysis Software Suite (xclass) software. The average rotation temperature of EA is higher than that of DE, whereas the average column density of EA is lower than that of DE. Combined with previous studies of hot cores and hot corinos, we find strong column density correlations among EA and DE (ρ = 0.92), EA and CH₃OH (ρ = 0.82), as well as DE and CH₃OH (ρ = 0.80). The column density ratios of EA/DE versus the column densities of CH₃OH remain nearly constant with values within ~1 order of magnitude. These strong correlations and the stable ratios, suggest that EA, DE, and CH₃OH could be chemically linked, with CH₃OH potentially serving as a precursor for EA and DE. Compared with chemical models, the three different warm-up time-scale models result in the systematic overproduction of EA and the systematic underproduction of DE. Therefore, our large sample observations can provide crucial constraints on chemical models.