Journal Article

Abundances and rotational temperatures of the C<sub><i>2</i></sub> interstellar molecule towards six reddened early-type stars*

M. Kaźmierczak, M. R. Schmidt, A. Bondar and J. Krełowski

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 4, pages 2548-2558
Published in print March 2010 | ISSN: 0035-8711
Published online March 2010 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2009.16065.x
Abundances and rotational temperatures of the C2 interstellar molecule towards six reddened early-type stars*

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Using high-resolution (∼85 000) and high signal-to-noise ratio (∼200) optical spectra acquired with the European Southern Observatory Ultraviolet and Visual Echelle Spectrograph, we have determined the interstellar column densities of C2 for six Galactic lines of sight with E(BV) ranging from 0.33 to 1.03. For our purposes, we identified and measured absorption lines belonging to the (1, 0), (2, 0) and (3, 0) Phillips bands A1Πu–X1Σ+g. We report on the identification of a few lines of the C2(4, 0) Phillips system towards HD 147889. The curve-of-growth method is applied to the equivalent widths to determine the column densities of the individual rotational levels of C2. The excitation temperature is extracted from the rotational diagrams. The physical parameters of the intervening molecular clouds (e.g. gas kinetic temperatures and densities of collision partners) were estimated by comparison with the theoretical model of excitation of C2.

Keywords: ISM: molecules

Journal Article.  6929 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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