A comprehensive analysis of a broadband 1.2 THz wide spectral survey of the Orion Kleinmann-Low nebula (Orion-KL) has shown that nitrogen bearing complex organics trace systematically hotter gas than O-bearing organics toward this source. The origin of this O/N dichotomy remains a mystery. If complex molecules originate from grain surfaces, N-bearing species may be more difficult to remove from grain surfaces than O-bearing organics. Theoretical studies, however, have shown that hot (T=300 K) gas phase chemistry can produce high abundances of N-bearing organics while suppressing the formation of O-bearing complex molecules. Measurement of gradients in isotopic fractionation at spatial scales commensurate with the forces driving this chemistry can distinguish these distinct formation pathways.<br/><br/>Isotopic fractionation is a relatively common tool in astrochemistry, however until recently it has not been possible to measure fractionation at high angular resolution. The Atacama Large Millimeter/Submillimeter Array (ALMA) combines the sensitivity and angular resolution required for these measurements, and represents a new method of approaching observational astrochemistry. We have obtained extremely high angular resolution observations of methyl cyanide (CH3CN) using the ALMA toward Orion KL. By simultaneously imaging 13CH3CN and CH2DCN we map the temperature structure and D/H ratio of CH3CN. We will present the results of these observations and discuss their implications for the formation of N-bearing organics in the interstellar medium.

Tracing the origins of nitrogen bearing organics toward Orion KL with ALMA

256th National Meeting (2018)

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