First Detection of Galactic Latitude Dedpendence of Near-infrared Diffuse Galactic Light from DIRBE Renalysis
Abstract
Observational study on near-infrared (IR) scattering properties of interstellar dust grains has been limited due to its faintness. Using all-sky maps obtained from the Diffuse Infrared Background Experiment, we investigate the scattering property from diffuse Galactic light (DGL) measurements at 1.25, 2.2, and 3.5 μ {{m}}, in addition to our recent analyses of diffuse near-IR emission. As a result, we first find that the intensity ratios of near-IR DGL to 100 μ {{m}} emission increase toward low Galactic latitudes at 1.25 and 2.2 μ {{m}}. The derived latitude dependence can be reproduced by a scattered light model of interstellar dust with a large scattering asymmetry factor g\equiv < {cos}θ > of {0.8}-0.3+0.2 at 1.25 and 2.2 μ {{m}}, assuming an infinite Galaxy disk as an illuminating source. The derived asymmetry factor is comparable to the values obtained in the optical, but several times larger than that expected from a recent dust model. Since a possible latitude dependence of ultraviolet-excited dust emission at 1.25 and 2.2 μ {{m}} would reduce the large asymmetry factor to the reasonable value, our result may indicate the first detection of such an additional emission component in the diffuse interstellar medium.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2016
- DOI:
- 10.3847/2041-8205/821/1/L11
- Bibcode:
- 2016ApJ...821L..11S
- Keywords:
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- dust;
- extinction;
- infrared: ISM;
- scattering