HCN and HNC mapping of the protostellar core Chamaeleon-MMS1

P. P. Tennekes, J. Harju, M. Juvela, L. Tóth

Research output: Contribution to journalArticle

31 Citations (Scopus)

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 Cha-MMS1 located in Chamaeleon I. Methods. The core was mapped in the J = 1-0 rotational lines of HCN, HNC, and HN13C. The column densities of H13CN, HN13C, H15NC and NH 3 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/H13CN column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN 13C/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 NH3. Using also previously determined column densities in Cha-MMS1, we can put the most commonly observed nitrogenous molecules in the following order according to their fractional abundances: Χ(NH3) > Χ(HC3N) > Χ(HNC) > Χ(HCN) > Χ(N2H+). Conclusions. The relationships between molecular abundances suggest that Cha-MMS1 represents an evolved chemical stage, experiencing at present the "late-time" cyanopolyyne peak. The possibility that the relatively high HNC/HCN ratio derived here is only valid for the 13C isotopic substitutes cannot be excluded on the basis of the present and other available data.

Original languageEnglish
Pages (from-to)1037-1043
Number of pages7
JournalAstronomy and Astrophysics
Volume456
Issue number3
DOIs
Publication statusPublished - Sep 2006

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fractionation
molecules
kinetics
substitutes
inversions
modeling
estimates
temperature
distribution
cold
inversion
method
chemical

Keywords

  • ISM: abundances
  • ISM: individual objects: Chamaeleon-MMS1
  • ISM: molecules

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

HCN and HNC mapping of the protostellar core Chamaeleon-MMS1. / Tennekes, P. P.; Harju, J.; Juvela, M.; Tóth, L.

In: Astronomy and Astrophysics, Vol. 456, No. 3, 09.2006, p. 1037-1043.

Research output: Contribution to journalArticle

Tennekes, P. P. ; Harju, J. ; Juvela, M. ; Tóth, L. / HCN and HNC mapping of the protostellar core Chamaeleon-MMS1. In: Astronomy and Astrophysics. 2006 ; Vol. 456, No. 3. pp. 1037-1043.
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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 Cha-MMS1 located in Chamaeleon I. Methods. The core was mapped in the J = 1-0 rotational lines of HCN, HNC, and HN13C. The column densities of H13CN, HN13C, H15NC and NH 3 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/H13CN column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN 13C/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 NH3. Using also previously determined column densities in Cha-MMS1, we can put the most commonly observed nitrogenous molecules in the following order according to their fractional abundances: Χ(NH3) > Χ(HC3N) > Χ(HNC) > Χ(HCN) > Χ(N2H+). Conclusions. The relationships between molecular abundances suggest that Cha-MMS1 represents an evolved chemical stage, experiencing at present the {"}late-time{"} cyanopolyyne peak. The possibility that the relatively high HNC/HCN ratio derived here is only valid for the 13C isotopic substitutes cannot be excluded on the basis of the present and other available data.",
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TY - JOUR

T1 - HCN and HNC mapping of the protostellar core Chamaeleon-MMS1

AU - Tennekes, P. P.

AU - Harju, J.

AU - Juvela, M.

AU - Tóth, L.

PY - 2006/9

Y1 - 2006/9

N2 - 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 Cha-MMS1 located in Chamaeleon I. Methods. The core was mapped in the J = 1-0 rotational lines of HCN, HNC, and HN13C. The column densities of H13CN, HN13C, H15NC and NH 3 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/H13CN column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN 13C/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 NH3. Using also previously determined column densities in Cha-MMS1, we can put the most commonly observed nitrogenous molecules in the following order according to their fractional abundances: Χ(NH3) > Χ(HC3N) > Χ(HNC) > Χ(HCN) > Χ(N2H+). Conclusions. The relationships between molecular abundances suggest that Cha-MMS1 represents an evolved chemical stage, experiencing at present the "late-time" cyanopolyyne peak. The possibility that the relatively high HNC/HCN ratio derived here is only valid for the 13C isotopic substitutes cannot be excluded on the basis of the present and other available data.

AB - 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 Cha-MMS1 located in Chamaeleon I. Methods. The core was mapped in the J = 1-0 rotational lines of HCN, HNC, and HN13C. The column densities of H13CN, HN13C, H15NC and NH 3 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/H13CN column density ratio is between 3 and 4, i.e. similar to values found in several other cold cores. The HN 13C/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 NH3. Using also previously determined column densities in Cha-MMS1, we can put the most commonly observed nitrogenous molecules in the following order according to their fractional abundances: Χ(NH3) > Χ(HC3N) > Χ(HNC) > Χ(HCN) > Χ(N2H+). Conclusions. The relationships between molecular abundances suggest that Cha-MMS1 represents an evolved chemical stage, experiencing at present the "late-time" cyanopolyyne peak. The possibility that the relatively high HNC/HCN ratio derived here is only valid for the 13C isotopic substitutes cannot be excluded on the basis of the present and other available data.

KW - ISM: abundances

KW - ISM: individual objects: Chamaeleon-MMS1

KW - ISM: molecules

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