Earth Planets Space, Vol. 62 (No. 1), pp. 63-67, 2010
Jian Gao1,2, B. W. Jiang1, and Aigen Li2
1Department of Astronomy, Beijing Normal University, Beijing, 100875, China
2Department of Physics and Astronomy, University of Missouri, bColumbia, Missouri 65211, USA
(Received August 10, 2008; Revised November 28, 2008; Accepted December 4, 2008; Online published February 12, 2010)
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 (AV) to the 9.7 μm Si-O optical depth (Δτ9.7 μm) and the ratio of AV to the 3.4 μm C-H optical depth (Δτ3.4 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).
Key words: Interstellar extinction, dust, silicate, aliphatic hydrocarbon, infrared astronomy.