Dynamical Zodiacal Cloud Models Constrained by High Resolution Spectroscopy of the Zodiacal Light (Icarus, in press)

TL;DR

This study models the Doppler shifts of zodiacal light caused by different dust sources and compares them with observations, revealing a significant contribution from cometary dust and estimating the dust composition and particle eccentricities.

Contribution

It provides the first detailed comparison of simulated Doppler shifts with high-resolution spectroscopic data to constrain the sources and properties of zodiacal dust.

Findings

Cometary dust significantly contributes to zodiacal light.

Approximately one-third of zodiacal dust originates from cometary particles.

Mean eccentricities of dust particles are estimated between 0.2 and 0.5.

Abstract

The simulated Doppler shifts of the solar Mg I Fraunhofer line produced by scattering on the solar light by asteroidal, cometary, and trans-Neptunian dust particles are compared with the shifts obtained by Wisconsin H-Alpha Mapper (WHAM) spectrometer. The simulated spectra are based on the results of integrations of the orbital evolution of particles. The deviation of the derived spectral parameters for various sources of dust used in the model reached maximum at the elongation (measured eastward from the Sun) between 90 deg and 120 deg. For the future zodiacal light Doppler shifts measurements, it is important to pay a particular attention to observing at this elongation range. At the elongations of the fields observed by WHAM, the model-predicted Doppler shifts were close to each other for several scattering functions considered. Therefore the main conclusions of our paper don't depend on a scattering function and mass distribution of particles if they are reasonable. A comparison of the dependencies of the Doppler shifts on solar elongation and the mean width of the Mg I line modeled for different sources of dust with those obtained from the WHAM observations shows that the fraction of cometary particles in zodiacal dust is significant and can be dominant. Cometary particles originating inside Jupiter's orbit and particles originating beyond Jupiter's orbit (including trans-Neptunian dust particles) can contribute to zodiacal dust about 1/3 each, with a possible deviation from 1/3 up to 0.1-0.2. The fraction of asteroidal dust is estimated to be about 0.3-0.5. The mean eccentricities of zodiacal particles located at 1-2 AU from the Sun that better fit the WHAM observations are between 0.2 and 0.5, with a more probable value of about 0.3.