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Title:
A survey of N2H(+) in dense clouds - Implications for interstellar nitrogen and ion-molecule chemistry
Authors:
Womack, M.; Ziurys, L. M.; Wyckoff, S.
Affiliation:
AA(Arizona State University, Tempe, AZ), AB(Arizona State University, Tempe, AZ), AC(Arizona State University, Tempe, AZ)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 387, March 1, 1992, p. 417-429. Research supported by Arizona State University. (ApJ Homepage)
Publication Date:
03/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
Azo Compounds, Interstellar Chemistry, Interstellar Matter, Molecular Clouds, Dark Matter, Electron Transitions, Emission Spectra, Formyl Ions, Molecular Rotation, Spectral Line Width
DOI:
10.1086/171094
Bibliographic Code:
1992ApJ...387..417W

Abstract

Attention is given to spectra of the N2(H(+) J = 1 - 0, J = 3 - 2 and (N-15)NH(+) and N(N-15)H(+) J = 1 - 0 rotational transitions obtained toward a sample of star-forming and cold dark clouds in the Galaxy. Toward the star-forming regions, line profiles are relatively narrow (typically 1-5 km/s) and show no evidence of line wings, in contrast to the spectra of HCO(+). It is inferred from the apparent absence of N2H(+) in hot, shocked gas that this ion may be a selective tracer of extended, quiescent material. Column densities of N2H(+) were found to be about 5 x 10 exp 12/sq cm toward cold clouds and about 10 exp 14/sq cm toward warm clouds. These values correspond to fractional abundances, relative to H2, of about 4 x 10 exp -10 toward both the warm and cold clouds. It is concluded that the abundance and distribution of N2H(+) is well explained by the ion-molecule chemistry, provided it has reached the steady state, as is found for interstellar NH3. The N2H(+) results are advanced as further evidence that interstellar nitrogen chemistry is anomalous.

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