Application of Nonspherical Dust Models to Polarization of Zodiacal Light Observed with DIRBE/COBE
4 affiliations
- 1The University of Tokyo
- 2Kyushu Institute of Technology
- 3Kwansei Gakuin University
- 4Tohoku University
Abstract
The composition, size, and shape of interplanetary dust (IPD) grains record their origin and are inferred from in situ counts and remote sensing of scattered sunlight and thermal emission. We previously reported near-infrared zodiacal light (ZL) polarization measured by the Diffuse Infrared Background Experiment (DIRBE) on board the Cosmic Background Explorer (COBE) at 1.25, 2.2, and 3.5 μ m, finding that absorptive micron-sized spheres reproduce it only partially and provide no plausible model for genuinely nonspherical silicate-carbonaceous mixtures. Here we combine light-scattering simulations of rough, irregular, and aggregate mixed-composition particles with the three-dimensional distribution of IPD cross-sectional area and compare predicted near-infrared ZL intensity and polarization with observations. Using an explicit χ ² criterion, exactly one of 2520 combinations of shape, size, size-distribution slope, and composition passes, and only marginally: large solid irregular grains at the ecliptic pole, at the largest size in the database. At the pole, the irregular-grain model reduces χ ² by a factor of 2.9 relative to the best Mie sphere (6.8 versus 19.4), which fails the χ ² < 7.815 criterion. At the ecliptic plane no model passes; spheres outperform irregular grains ( χ ² = 9.1 versus 20.8) but still fail, so no single population describes both regions. Compact aggregates, including low-porosity ones that most resemble the pole polarization, fail at both latitudes, and fluffy fractal aggregates fail by the widest margin. The acceptable combination uses the less absorptive composition, pointing to low absorptivity for the IPD sampled toward the ecliptic pole.
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BibTeX
@article{takimoto2026application,
title = {{Application of Nonspherical Dust Models to Polarization of Zodiacal Light Observed with DIRBE/COBE}},
author = {Kohji Takimoto and Kei Sano and Shuji Matsuura and Kohji Tsumura},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aeab88},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeab88},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Application of Nonspherical Dust Models to Polarization of Zodiacal Light Observed with DIRBE/COBE
AU - Kohji Takimoto
AU - Kei Sano
AU - Shuji Matsuura
AU - Kohji Tsumura
PY - 2026
DA - 2026/10/19
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aeab88
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aeab88
AB - The composition, size, and shape of interplanetary dust (IPD) grains record their origin and are inferred from in situ counts and remote sensing of scattered sunlight and thermal emission. We previously reported near-infrared zodiacal light (ZL) polarization measured by the Diffuse Infrared Background Experiment (DIRBE) on board the Cosmic Background Explorer (COBE) at 1.25, 2.2, and 3.5 μ m, finding that absorptive micron-sized spheres reproduce it only partially and provide no plausible model for genuinely nonspherical silicate-carbonaceous mixtures. Here we combine light-scattering simulations of rough, irregular, and aggregate mixed-composition particles with the three-dimensional distribution of IPD cross-sectional area and compare predicted near-infrared ZL intensity and polarization with observations. Using an explicit χ ² criterion, exactly one of 2520 combinations of shape, size, size-distribution slope, and composition passes, and only marginally: large solid irregular grains at the ecliptic pole, at the largest size in the database. At the pole, the irregular-grain model reduces χ ² by a factor of 2.9 relative to the best Mie sphere (6.8 versus 19.4), which fails the χ ² < 7.815 criterion. At the ecliptic plane no model passes; spheres outperform irregular grains ( χ ² = 9.1 versus 20.8) but still fail, so no single population describes both regions. Compact aggregates, including low-porosity ones that most resemble the pole polarization, fail at both latitudes, and fluffy fractal aggregates fail by the widest margin. The acceptable combination uses the less absorptive composition, pointing to low absorptivity for the IPD sampled toward the ecliptic pole.
SN - 0004-637X
SN - 1538-4357
ER -