Detection of the Ammonium Ion in Space
Abstract
We report on the detection of a narrow feature at 262816.73 MHz toward Orion and the cold prestellar core B1-bS which we attribute to the 10-00 line of the deuterated ammonium ion, NH3D+. The observations were performed with the IRAM 30 m radio telescope. The carrier has to be a light molecular species as it is the only feature detected over 3.6 GHz of bandwidth. The hyperfine structure is not resolved, indicating a very low value for the electric quadrupolar coupling constant of nitrogen which is expected for NH3D+ as the electric field over the N nucleus is practically zero. Moreover, the feature is right at the predicted frequency for the 10-00 transition of the ammonium ion, 262817 ± 6 MHz (3σ), using rotational constants derived from new infrared data obtained in our laboratory in Madrid. The estimated column density is (1.1 ± 0.2) × 1012 cm-2. Assuming a deuterium enhancement similar to that of NH2D, we derive N(NH_4^+) ~= 2.6 × 1013 cm-2, i.e., an abundance for ammonium of a few 10-11.
This work was based on observations carried out with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain)- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2013
- DOI:
- 10.1088/2041-8205/771/1/L10
- arXiv:
- arXiv:1306.3364
- Bibcode:
- 2013ApJ...771L..10C
- Keywords:
-
- ISM: abundances;
- ISM: individual objects: B1-bS;
- ISM: molecules;
- line: identification;
- molecular data;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in the Astrophysical Journal Letters 04 June 2013