Thermal emission from the amorphous dust: An alternative possibility of the origin of the anomalous microwave emission

TL;DR

This study models thermal emission from amorphous dust using the TLS model, successfully fitting observed microwave to infrared spectra and proposing an alternative explanation for anomalous microwave emission without new species.

Contribution

It is the first to self-consistently apply the TLS model to fit observed SEDs of AME in molecular clouds, offering a new interpretation of AME origin.

Findings

TLS model accurately reproduces observed SEDs of AME

Amorphous dust resonance emission can explain AME without new species

Model predicts higher polarization fractions than observed, suggesting further refinement

Abstract

Complete studies of the radiative processes of thermal emission from the amorphous dust from microwave through far infrared wavebands are presented by taking into account, self-consistently for the first time, the standard two-level systems (TLS) model of amorphous materials. The observed spectral energy distributions (SEDs) for the Perseus molecular cloud (MC) and W43 from microwave through far infrared are fitted with the SEDs calculated with the TLS model of amorphous silicate. We have found that the model SEDs well reproduce the observed properties of the anomalous microwave emission (AME). The present result suggests an alternative interpretation for the AME being carried by the resonance emission of the TLS of amorphous materials without introducing new species. Simultaneous fitting of the intensity and polarization SEDs for the Perseus MC and W43 are also performed. The amorphous model reproduces the overall observed feature of the intensity and polarization SEDs of the Perseus MC and W43. However, the model's predicted polarization fraction of the AME is slightly higher than the QUIJOTE upper limits in several frequency bands. A possible improvement of our model to resolve this problem is proposed. Our model predicts that interstellar dust is amorphous materials having very different physical characteristics compared with terrestrial amorphous materials.