Interplanetary Dust as a Foreground for the LiteBIRD CMB Satellite Mission

TL;DR

This paper assesses the impact of interplanetary dust emission as a foreground contaminant for the LiteBIRD CMB satellite, estimating its detectability and potential to mimic primordial B Modes, and discusses mitigation strategies.

Contribution

It provides the first detailed estimates of interplanetary dust emission contamination for LiteBIRD, including polarization effects, and evaluates its significance relative to Galactic foregrounds.

Findings

LiteBIRD can detect interplanetary dust emission in total power across all bands.

Polarization fraction of interplanetary dust could induce B Modes comparable to r=0.001.

Interplanetary dust emission is variable and may complicate data analysis but is not the primary obstacle.

Abstract

As ever-more sensitive experiments are made in the quest for primordial CMB B Modes, the number of potentially significant astrophysical contaminants becomes larger as well. Thermal emission from interplanetary dust, for example, has been detected by the Planck satellite. While the polarization fraction of this Zodiacal, or interplanetary dust emission (IPDE) is expected to be low, it is bright enough to be detected in total power. Here, estimates of the magnitude of the effect as it might be seen by the LiteBIRD satellite are made. The COBE IPDE model from Kelsall et al. (1998) is combined with a model of the LiteBIRD experiment's scanning strategy to estimate potential contamination of the CMB in both total power and in polarization power spectra. LiteBIRD should detect IPDE in temperature across all of its bands, from 40 through 402 GHz, and should improve limits on the polarization fraction of IPDE at the higher end of this frequency range. If the polarization fraction of IPDE is of order 1%, the current limit from ISO/CAM measurements in the mid-infrared, it may induce large-scale polarization B Modes comparable to cosmological models with an r of order 0.001. In this case, the polarized IPDE would also need to be modeled and removed. As a CMB foreground, IPDE will always be subdominant to Galactic emissions, though because it caused by emission from grains closer to us, it appears variable as the Earth travels around the Sun, and may thereby complicate the data analysis somewhat. But with an understanding of some of the symmetries of the emission and some flexibility in the data processing, it should not be the primary impediment to the CMB polarization measurement.