Polarization Spectrum of Near-Infrared Zodiacal Light Observed with CIBER

Abstract

We report the first measurement of the zodiacal light (ZL) polarization spectrum in the near-infrared between 0.8 and 1.8 μm. Using the low-resolution spectrometer on board the Cosmic Infrared Background Experiment, calibrated for absolute spectrophotometry and spectropolarimetry, we acquire long-slit polarization spectral images of the total diffuse sky brightness toward five fields. To extract the ZL spectrum, we subtract the contribution of other diffuse radiation, such as the diffuse galactic light, the integrated starlight, and the extragalactic background light. 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 ∼20%, which is consistent with an earlier observation from the Diffuse Infrared Background Experiment on board on the Cosmic Background Explorer. The measured degree of polarization and its solar elongation dependence are reproduced by an empirical scattering model in the visible band and also by a Mie scattering model for large absorptive particles, while a Rayleigh scattering model is ruled out. All of our results suggest that the interplanetary dust is dominated by large particles.

Near-infrared Polarization Charateristics of the Zodiacal Light Observed with DIRBE/COBE

“…Compared to the average value from Berriman et al (1994), our results are higher by more than 5%. On the other hand, the degree of polarization at 1.25 and 2.2 μm, removed starlight, and other contributions by Takimoto et al (2022) are consistent with this work. The polarization due to graphite (Draine & Lee 1984) with particle radii greater than 10 μm, based on Mie theory calculations, shows a tendency to decrease toward longer wavelengths, different from our results.…”

“…More recently, ZL polarization has been measured in the near-infrared. The ZL polarization spectrum from λ = 0.8 μm to 1.8 μm observed by CIBER (Takimoto et al 2022) also (Pitz et al 1979). Blue triangles: Skylab at the north celestial pole (Weinberg & Hahn 1980).…”

“…Purple stars: an average of three similar results (OSO-5 at ò = 90°; Sparrow & Ney 1972; balloon observation at ò = 30°; Van de Noord 1970; ground-based observation at ò = 39°; Wolstencroft & Brandt 1967). Black diamonds: CIBER at the north ecliptic pole (Takimoto et al 2022). Aqua crosses and orange inverted triangles: DIRBE at β = 0°, ò = 90° (Berriman et al 1994;Takimoto et al2022).…”

“…Berriman et al (1994) reported the ZL polarization in the ecliptic plane (ecliptic latitude β = 0°) at solar elongation ò = 90°using only one week of observations, but diffuse radiation and starlight were not subtracted in all wavelength bands, and the 3.5 μm results include a thermal radiation component of the ZL. Takimoto et al (2022) also estimated the ZL polarization at 1.25 and 2.2 μm from the DIRBE result presented in Berriman et al (1994), but the ZL polarization shows little dependence on λ after other diffuse light sources are considered (Arendt et al 1998;Cambrésy et al 2001;Girardi et al 2005;Skrutskie et al 2006;Tsumura et al 2013;Arai et al 2015).…”

COSMOGLOBE: Simulating zodiacal emission with ZodiPy

“…Polarization from thermal emission from ZE has never been detected, and it is expected to be less than 1 % (Weinberg & Hahn 1980;Onaka 2000;Ganga et al 2021). The scattered sunlight is known to be polarized as a function of the scanning strategy with the scattering angle and elongation, as shown in Berriman et al (1994) and Takimoto et al (2022), for example. Allowing the user to predict the polarized emission at wavelengths where the ZE is dominated by scattered sunlight (1-5 µm) would help with forecasting for future polarized experiments.…”