Measurements of the Zodiacal Light Absolute Intensity through Fraunhofer Absorption Line Spectroscopy with CIBER

TL;DR

This study measures the absolute intensity of Zodiacal Light using Fraunhofer line spectroscopy with CIBER, testing existing models and suggesting a modified model with an offset parameter to better fit the data.

Contribution

Introduces a novel spectroscopic technique to measure Zodiacal Light intensity and evaluates existing models, proposing a simple modification for improved accuracy.

Findings

The Wright model fits the data better than the Kelsall model.

A modified Kelsall model with an offset parameter describes the data well.

Measured Zodiacal Light intensity suggests a dust component not strongly modulated by Earth's motion.

Abstract

Scattered sunlight from the interplanetary dust (IPD) cloud in our Solar system presents a serious foreground challenge for spectro-photometric measurements of the Extragalactic Background Light (EBL). In this work, we report on measurements of the absolute intensity of the Zodiacal Light (ZL) using the novel technique of Fraunhofer line spectroscopy on the deepest 8542 Angstrom line of the near-infrared CaII absorption triplet. The measurements are performed with the Narrow Band Spectrometer (NBS) aboard the Cosmic Infrared Background Experiment (CIBER) sounding rocket instrument. We use the NBS data to test the accuracy of two ZL models widely cited in the literature; the Kelsall and Wright models, which have been used in foreground removal analyses that produce high and low EBL results respectively. We find a mean reduced chi squared of 3.5 for the Kelsall model and a chi squared of 2.0 for the Wright model. The best description of our data is provided by a simple modification to the Kelsall model which includes a free ZL offset parameter. This adjusted model describes the data with a reduced chi squared of 1.5 and yields an inferred offset amplitude of 46 +- 19 nW m^-2 sr^-1 extrapolated to 12500 Angstroms. These measurements elude to the potential existence of a dust cloud component in the inner Solar system whose intensity does not strongly modulate with the Earth's motion around the Sun.