Modeling Long-wavelength Amorphous Dust Emission Based on the Physically Motivated Soft-potential Model

Abstract We propose a new amorphous dust emission model based on the soft-potential (SP) model, applicable in the long-wavelength range from the far-infrared to the microwave. The SP model is widely accepted in material physics to explain amorphous thermal properties and is an extension of the two-level systems (TLS) model, which has been applied in interstellar amorphous dust physics. In the SP model, by assuming that some atoms composing amorphous dust are trapped in a double-well potential (DWP) described by a quartic function, the electric interaction can be solved directly, allowing the absorption cross section of the amorphous dust to be calculated. We present numerical and analytical solutions for the absorption cross section of amorphous dust and compare these results, finding good agreement for the DWP with a sufficiently high potential barrier. Our findings show that the SP model can reproduce the observed spectrum of the Perseus molecular cloud with slightly better accuracy than the conventional TLS model. Additionally, the SP model can more effectively explain various long-wavelength dust emission features, such as the spectrum flattening in the submillimeter range and anomalous microwave emission, compared to the TLS model. Further comparison and verification with observational data and laboratory measurements are necessary to refine the model.