Spinning dust emission: the effect of rotation around a non-principal axis

TL;DR

This paper studies how dust grains rotating around non-principal axes affect spinning dust emission, revealing that such rotation leads to higher emissivities and peak frequencies in the emission spectra.

Contribution

It introduces a new model for spinning dust emission considering non-principal axis rotation, updating excitation and damping rates for more accurate spectra predictions.

Findings

Spectra show increased emissivity and peak frequency due to non-principal axis rotation.

Randomized nutation states during thermal spikes influence emission characteristics.

Updated calculations improve alignment with observed interstellar dust emission.

Abstract

We investigate the rotational emission from dust grains that rotate around non- principal axes. We argue that in many phases of the interstellar medium, the smallest grains, which dominate spinning dust emission, are likely to have their nutation state (orientation of principal axes relative to the angular momentum vector) randomized during each thermal spike. We recompute the excitation and damping rates associated with rotational emission from the grain permanent dipole, grain-plasma interactions, infrared photon emission, and collisions. The resulting spinning dust spectra gener- ally show a shift toward higher emissivities and peak frequencies relative to previous calculations.