TY - JOUR
T1 - FIRST DETECTION OF GALACTIC LATITUDE DEPENDENCE OF NEAR-INFRARED DIFFUSE GALACTIC LIGHT FROM DIRBE RENALYSIS
AU - Sano, K.
AU - Matsuura, S.
AU - Tsumura, K.
AU - Arai, T.
AU - Shirahata, M.
AU - Onishi, Y.
N1 - Funding Information:
We acknowledge useful discussions with K. Kawara, H. Kataza, and Y. Matsuoka. We are grateful to the anonymous referee for a number of useful comments that greatly improved the paper. K.S. is supported by Grant-in-Aid for Japan Society for the Promotion of Science (JSPS) Fellows. This publication uses the COBE data sets developed by the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center under the guidance of the COBE Science Working Group. This publication also makes use of data products from the Two Micron All-Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and the National Science Foundation. This publication also makes use of data products from WISE, which is a joint project between the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology. WISE is funded by NASA.
Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.
PY - 2016/4/10
Y1 - 2016/4/10
N2 - 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 μm, 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 μm emission increase toward low Galactic latitudes at 1.25 and 2.2 μm. The derived latitude dependence can be reproduced by a scattered light model of interstellar dust with a large scattering asymmetry factor g ≡ 'cos θ' of 0.8-0.3+0.2 at 1.25 and 2.2 μm, 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 μm 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.
AB - 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 μm, 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 μm emission increase toward low Galactic latitudes at 1.25 and 2.2 μm. The derived latitude dependence can be reproduced by a scattered light model of interstellar dust with a large scattering asymmetry factor g ≡ 'cos θ' of 0.8-0.3+0.2 at 1.25 and 2.2 μm, 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 μm 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.
KW - dust, extinction
KW - infrared: ISM
KW - scattering
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U2 - 10.3847/2041-8205/821/1/L11
DO - 10.3847/2041-8205/821/1/L11
M3 - Article
AN - SCOPUS:84964225040
SN - 2041-8205
VL - 821
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L11
ER -