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7.4. The 3.4 micron absorption in the Galactic center sources

Published online by Cambridge University Press:  25 May 2016

T. Nagata*
Affiliation:
Department of Physics, Nagoya University, Nagoya 464-01, Japan

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The 3.4μm absorption feature, first detected in the Galactic center source IRS7 (Soifer et al., 1976), has been observed in other Galactic center sources IRS3, IRS12 (McFadzean et al., 1989), and IRS6E (Pendleton et al., 1994). This feature is regarded as characteristic of dust in the diffuse interstellar medium, and attributed to C-H stretching vibrations. Several objects in the lines of sight other than the Galactic center is now known to have the feature (Sandford et al. 1995 and references therein; Imanishi et al. 1996). The absorption depths per unit visual extinction τ3.4/AV for these sources are compared with those for the Galactic center sources, and they are thought to increase near the Galactic center. However, the “Galactic center” sources are all in the central parsec cluster, and the features observed in them may be only representative of interstellar medium local to the central parsec, not the general diffuse interstellar medium of the inner Galaxy. In this paper, we report the 3.4μm absorption feature detected in near-infrared sources within 1° of the Galactic center.

Type
Part II. Nuclear Interstellar Medium
Copyright
Copyright © Kluwer 1998 

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