Toward understanding the 3 . 4 μ m and 9 . 7 μ m extinction feature variations from the local diffuse interstellar medium to the Galactic center
نویسندگان
چکیده
Observationally, both the 3.4 µm aliphatic hydrocarbon C–H stretching absorption feature and the 9.7 µm amorphous silicate Si–O stretching absorption feature show considerable variations from the local diffuse interstellar medium (ISM) to Galactic center (GC): both the ratio of the visual extinction (A V) to the 9.7 µm Si–O optical depth (∆τ 9.7 µm) and the ratio of A V to the 3.4 µm C–H optical depth (∆τ 3.4 µm) of the solar neighborhood local diffuse ISM are about twice as much as that of the GC. In this work, we try to explain these variations in terms of a porous dust model consisting of a mixture of amorphous silicate, carbonaceous organic refractory dust (as well as water ice for the GC dust).
منابع مشابه
SPECTROPOLARIMETRY OF THE 3.4 m FEATURE IN THE DIFFUSE ISM TOWARD THE GALACTIC CENTER QUINTUPLET CLUSTER
Aliphatic hydrocarbons exhibit an absorption feature at 3.4 m, observed toward sources that sample diffuse regions of the interstellar medium (ISM). The absorbers responsible for this feature are assumed to reside in some component of interstellar dust, but the physical nature of the particles (size, shape, structure, etc.) is uncertain. Observations of interstellar polarization provide discrim...
متن کاملISO - SWS observations of infrared absorption bands of the diffuse interstellar medium : The 6 . 2 μ m feature of aromatic compounds ?
We present ISO-SWS spectroscopy of eight strong infrared sources with large extinction through the diffuse interstellar medium. These are five late-type Wolf-Rayet stars, the blue hypergiant Cyg OB2 #12 and the Galactic Center Sources 3 and 4. The spectra show a number of absorption features that can be ascribed to interstellar dust and gas. Features at 3.0, 3.4, 4.66 and 5.95 μm were already k...
متن کاملPixie Dust : The Silicate Features in the Diffuse Interstellar Medium
We have analyzed the 9.7 and " 18 " µm interstellar silicate absorption features along the line of sight toward four heavily extincted galactic WC-type Wolf-Rayet (WR) stars. We construct two interstellar extinction curves from 1.25 to 25 µm using near-IR extinction measurements from the literature along with the sili-cate profiles of WR 98a (representing the local ISM) and GCS 3 (representing ...
متن کاملDetection of in the Diffuse Interstellar Medium: the Galactic Center
Absorption lines of have been detected in the spectra of two infrared sources in the Galactic 3 center and also toward the heavily reddened star Cygnus OB2 No. 12, whose line of sight is believed to include only di†use interstellar gas. The absorptions toward the Galactic center sources (IRS 3 and GCS 3-2) probably are due to both in di†use gas and in molecular clouds. The ratios of line equiva...
متن کامل3.4 Micron Feature on the Shoulder of Ice-band Absorptions in Three Luminous Young Stellar Objects: Iras 18511+0146, Iras 21413+5442, and Iras 04579+4703
An absorption feature at 3.4 lm has been detected in the long-wavelength wing of the 3.1 lm H2O ice feature in three young stellar objects: IRAS 18511+0146, IRAS 21413+5442, and IRAS 04579+4703. The profile of the 3.4 lm absorption in IRAS 18511+0146 has distinct subfeatures at 3.38, 3.41, and 3.48 lm and is not similar to those found in molecular clouds but is similar to those in the diffuse i...
متن کامل