Cosmic Amorphous Dust Model as the Origin of Anomalous Microwave Emission

TL;DR

This paper introduces the cosmic amorphous dust model (CAD), explaining anomalous microwave emission through amorphous silicate and carbon dust, with predictions matching observed polarization spectra and emphasizing the unique properties of amorphous carbon in interstellar dust.

Contribution

The paper presents a novel dust model (CAD) that accounts for both intensity and polarization spectra of molecular clouds, linking AME to amorphous carbon and silicate dust.

Findings

AME originates from TLS in amorphous carbon dust.

Polarized emission in submillimeter bands comes from amorphous silicate dust.

Model predicts polarization fractions consistent with observations.

Abstract

We have shown that the thermal emission of the amorphous dust composed of amorphous silicate dust (a-Si) and amorphous carbon dust (a-C) provides excellent fit both to the observed intensity and the polarization spectra of molecular clouds. The anomalous microwave emission (AME) originates from the resonance transition of the two-level systems (TLS) attributed to the a-C with an almost spherical shape. On the other hand, the observed polarized emission in submillimeter wavebands is coming from a-Si. By taking into account a-C, the model prediction of the polarization fraction of the AME is reduced dramatically. Our model prediction of the 3$\sigma$ lower limits of the polarization fraction of the Perseus and W 43 molecular clouds at 17 GHz are $8.129 \times 10^{-5}$ and $8.012 \times 10^{-6}$, respectively. The temperature dependence of the heat capacity of a-C shows the peculiar behavior compared with that of a-Si. So far, the properties of a-C are unique to interstellar dust grains. Therefore, we coin our dust model as the cosmic amorphous dust model (CAD).