Exploring Molecular Complexity with ALMA: Deuterated complex organic molecules in Sgr B2

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
² I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
³ Depts. of Astronomy and Chemistry, University of Virginia, Charlottesville, VA 22904, USA

Abstract

Apart from the case of methanol, little is known about deuterium fractionation of complex organic molecules in the interstellar medium, especially in high mass star forming regions. We take advantage of the EMoCA spectral line survey to search for deuterated complex organic molecules toward the hot molecular core Sgr B2(N2). We report the secure detection of CH₂DCN with a deuteration level of 0.4% and tentative detections of CH₂DOH, CH₂DCH₂CN, CH₃CHDCN, and DC₃N with levels in the range 0.05–0.12%. Except for methyl cyanide, the measured deuteration levels lie at least a factor of four below the predictions of current astrochemical models. They are also lower than in Orion KL by a factor of a few up to a factor ten. These discrepancies and differences may be due to the higher temperatures that prevail in the Galactic Center region compared to nearby clouds, or they may result from a lower overall abundance of deuterium itself in the Galactic Center region by up to a factor ten.