A Rigorous Attempt to Verify Interstellar Glycine

In 2003, Kuan, Charnley, and co-workers reported the detection of interstellar glycine (NH2CH2COOH) based on observations of 27 lines in 19 different spectral bands in one or more of the sources Sgr B2(N-LMH), Orion KL, and W51 e1/e2. They supported their detection report with rotational temperature diagrams for all three sources. In this paper, we present essential criteria which can be used in a straightforward analysis technique to confirm the identity of an interstellar asymmetric rotor such as glycine. We use new laboratory measurements of glycine as a basis for applying this analysis technique, both to our previously unpublished 12 m telescope data and to the previously published SEST data of Nummelin and colleagues. We conclude that key lines necessary for an interstellar glycine identification have not yet been found. We identify some common molecular candidates that should be examined further as more likely carriers of several of the lines reported as glycine. Finally, we illustrate that a rotational Department of Astronomy, University of Illinois, Urbana, IL 61801 email: [email protected], [email protected], [email protected] Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, MD 208998441 email: [email protected] Earth and Space Data Computing Div., Code 930, NASA’s Goddard Space Flight Center, Greenbelt, MD 20771 email: [email protected] National Radio Astronomy Observatory, Green Bank, WV 24944-0002 email: [email protected] National Research Council Resident Research Associate Institute of Radio Astronomy of NASU, Krasnoznamennaya 4, 61002 Kharkow, Ukraine email: [email protected]; [email protected]