Interstellar absorption lines toward Cep OB4

Details Interstellar absorption lines toward Cep OB4 Interstellar absorption lines toward Cep OB4

Oct 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004a%26a...425..151g&link_type=abstract

Astronomy and Astrophysics, v.425, p.151-162 (2004)

Astronomy and Astrophysics

Astrophysics

5

Ism: Abundances, Ism: Clouds, Ism: Molecules, Ism: Lines And Bands

Scientific paper

An analysis of optical echelle spectra towards nine stars in the Cep OB4 association is presented. Interstellar absorption lines which arise in the (1, 0) and (2, 0) bands of the CN A 2Π - X 2Σ+ red system towards BD+66o 1661, BD+66o 1674, and BD+66o 1675 are used to infer accurate CN column densities N(CN). A comparison with earlier measurements in the CN violet system allows to infer a CN Doppler b parameter of b(CN) = 1.2{-}2.4 km s-1. Molecular carbon absorption lines which arise in the (1, 0), (2, 0) and (3, 0) bands of the C2 A1Πu - X1Σg+ Phillips system is used to infer gaskinetic temperatures of 35±10 K and densities of n = 700 ± 200 cm-3 towards BD+66o 1661 and BD+66o 1675, and a temperature of 60±10 K and a density of 800 ± 400 cm-3 towards BD+66o 1674. The R(1) line of the (0, 0) band of the CH A2Δ - X2Π system is detected towards 6 stars. A tight correlation exists between N(C2) and N(CH). N(CN) increases with N(CH) and with N(C2). Interstellar CH+ is marginally detected towards four stars. Inferred CH+ column densities are significantly lower than towards other lines of sight with similar reddening. The velocity structure towards Cep OB4 and the chemical abundances suggest that CN, C2, CH, and CH+ are formed in quiescent material. A previous suggestion that the molecules form in a photon-dominated region close to the stars is not supported by the observations.
Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofisica de Andalucia (CSIC).

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