First detection of NH₃ ($\mathsf{1_0 \rightarrow 0_0}$) from a low mass cloud core

Abstract

Odin has successfully observed the molecular core Oph A in the 572.5 GHz rotational ground state line of ammonia, NH 3 (J K = 1 0 0 0 ). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C 17 O and CH 3 OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH 3 OH) = 3 10 -9 . Unless NH 3 is not entirely segregated from C 17 O and CH 3 OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH 3 ) = 8 10 -10 .