Spectropolarimetric constraints on the nature of the 3.4 micron absorber in the interstellar medium

Citation
Aj. Adamson et al., Spectropolarimetric constraints on the nature of the 3.4 micron absorber in the interstellar medium, ASTROPHYS J, 512(1), 1999, pp. 224-229
Citations number
55
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004637X → ACNP
Volume
512
Issue
1
Year of publication
1999
Part
1
Pages
224 - 229
Database
ISI
SICI code
0004-637X(19990210)512:1<224:SCOTNO>2.0.ZU;2-3
Abstract
Spectropolarimetry of the 3.4 mu m aliphatic C-H stretch feature, generally attributed to carbonaceous dust in the diffuse interstellar medium, has be en carried out in the line of sight from the Galactic center source Sagitta rius A IRS 7. The feature is unpolarized (Delta p/Delta tau < 0.2): the upp er limit for polarization is well below that expected on the basis of a mod el in which the carrier molecules are associated with the aligned silicate component of interstellar dust, for example, as an organic or carbonaceous mantle on a silicate core. The simplest explanation is that the 3.4 mu m ca rrier resides in a population of small, nonpolarizing carbonaceous grains, physically separate from the silicates and sharing many characteristics wit h the carriers of the 217.5 nm extinction bump.