Polarization spectrum of near infrared zodiacal light observed with CIBER

TL;DR

This study presents the first near-infrared polarization spectrum of zodiacal light, revealing that interplanetary dust is mainly composed of large particles, with polarization varying by ecliptic coordinates and solar elongation.

Contribution

First measurement of near-infrared zodiacal light polarization spectrum, providing new insights into interplanetary dust particle size and scattering properties.

Findings

Zodiacal light polarization shows little wavelength dependence in near-infrared.

Maximum polarization of ~20% observed at North Ecliptic Pole.

Results support large particle dominance, ruling out Rayleigh scattering.

Abstract

We report the first measurement of the zodiacal light (ZL) polarization spectrum in the near-infrared between 0.8 and 1.8 $\mu$m. Using the low-resolution spectrometer (LRS) on board the Cosmic Infrared Background Experiment (CIBER), calibrated for absolute spectrophotometry and spectropolarimetry, we acquire long-slit polarization spectral images of the total diffuse sky brightness towards five fields. To extract the ZL spectrum, we subtract contribution of other diffuse radiation, such as the diffuse galactic light (DGL), the integrated star light (ISL), and the extragalactic background light (EBL). The measured ZL polarization spectrum shows little wavelength dependence in the near-infrared and the degree of polarization clearly varies as a function of the ecliptic coordinates and solar elongation. Among the observed fields, the North Ecliptic Pole shows the maximum degree of polarization of $\sim$ 20$\%$, which is consistent with an earlier observation from the Diffuse Infrared Background Experiment (DIRBE) aboard on the Cosmic Background Explorer (COBE). The measured degree of polarization and its solar elongation dependence are reproduced by the empirical scattering model in the visible band and also by the Mie scattering model for large absorptive particles, while the Rayleigh scattering model is ruled out. All of our results suggest that the interplanetary dust is dominated by large particles.