HCN and HNC mapping of the protostellar core Chamaeleon-MMS1
Abstract
Aims.The purpose of this study is to investigate the distributions of the isomeric molecules HCN and HNC and estimate their abundance ratio in the protostellar core
Methods: .The core was mapped in the J=1-0 rotational lines of HCN, HCN, and HN13C. The column densities of HN13C, HN13C, H15NC and NH3 were estimated towards the centre of the core.
Results: .The core is well delineated in all three maps. The kinetic temperature in the core, derived from the NH3 (1, 1) and (2, 2) inversion lines, is 12.1 ± 0.1 K. The HN13C/HN13C column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN13C/H15NC column density ratio is ∼ 7. In case no 15N fractionation occurs in HNC (as suggested by recent modelling results), the HNC/HN13C abundance ratio is in the range 30-40, which indicates a high degree of 13C fractionation in HNC. Assuming no differential 13C fractionation the HCN and HNC abundances are estimated to be ∼ 7 × 10-10 and ∼ 2× 10-9, respectively, the former being nearly two orders of magnitude smaller than that of NH_3. Using also previously determined column densities in
Conclusions: .The relationships between molecular abundances suggest that
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2006
- DOI:
- 10.1051/0004-6361:20040294
- arXiv:
- arXiv:astro-ph/0606547
- Bibcode:
- 2006A&A...456.1037T
- Keywords:
-
- ISM: individual objects: Chamaeleon-MMS1;
- ISM: abundances;
- ISM: molecules;
- Astrophysics
- E-Print:
- 9 pages, 8 figures, accepted for publication in Astronomy &