The Spatial Distribution of Organics Toward the High-mass YSO NGC 7538 IRS9

摘要: Complex molecules have been broadly classified into three generations dependent on the mode of formation and required temperature ({lt}25, 25-100 K, {gt}100 K). Around massive young stellar objects (MYSOs), icy grain mantles gas are exposed to increasingly higher temperatures as material accretes from outer envelope in toward central hot region. The combination this profile generational chemistry should result a changing complex molecular composition with radius around MYSOs. We combine IRAM 30 m Submillimeter Array observations explore spatial distribution organic high-mass object NGC 7538 IRS9, whose weak molecule emission previously escaped detection. find that N-bearing organics CH$_{3}$OH present substantial increases 8000 AU R {lt} 3000 AU, while unsaturated O-bearing hydrocarbons do not. increase line flux for some envelope, or 25 is consistent recent model predictions an onset ice at 20-30 K. many same suggests presence core, where thermal evaporation gas-phase reactions drive chemistry. thus form all radii protostar, but changes dramatically increases, which used together adapted gas-grain astrochemical constrain chemical generation(s) different classes belong.