First detection of NH 3 (1 0 → 0 0) from a low mass cloud core. On the low ammonia abundance of the ρ Oph A core

Abstract

Odin has successfully observed the molecular core ρ 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 17O and CH 3OH) 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 3OH) = 3 × 10 -9. Unless NH 3 is not entirely segregated from C 17O and CH 3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH 3) = 8 × 10 -10.