Abstract
We review the major progress on the modeling of electric dipole emission from rapidly spinning tiny dust grains, including polycyclic aromatic hydrocarbons (PAHs). We begin by summarizing the original model of spinning dust proposed by Draine and Lazarian and recent theoretical results improving the Draine and Lazarian model. The paper is focused on important physical effects that were disregarded in earlier studies for the sake of simplicity and recently accounted for by us, including grain wobbling due to internal relaxation, impulsive excitation by single-ion collisions, the triaxiality of grain shape, charge fluctuations, and the turbulent nature of astrophysical environments. Implications of the spinning dust for constraining the physical properties of ultrasmall dust grains and environmental conditions are discussed. We discuss the alignment of tiny dust grains and the possibility of polarized spinning dust emission. Suggestions for constraining the alignment of tiny grains and polarization of spinning dust are also discussed.
Highlights
Diffuse Galactic microwave emission carries important information on the fundamental properties of the interstellar medium, but it interferes with cosmic microwave background (CMB) experiments
Precision cosmology with Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellite requires a good model of the microwave foreground emission to allow for reliable subtraction of Galactic contamination from the CMB radiation
While the DL98 model appears to be in general agreement with observations, it did not account for Advances in Astronomy some important effects, namely, the nonsphericity of grain shapes, the internal relaxation within grain, and the transient spinup due to ion collisions
Summary
Diffuse Galactic microwave emission carries important information on the fundamental properties of the interstellar medium, but it interferes with cosmic microwave background (CMB) experiments (see Bouchet et al [1] and Tegmark et al [2]). In the paper by De Oliveira-Costa et al [5], this emission was nicknamed “Foreground X,” which properly reflects its mysterious nature This component is spatially correlated with 100 μm thermal dust emission, but its intensity is much higher than one would expect by directly extrapolating the thermal dust emission spectrum to the microwave range. While the DL98 model appears to be in general agreement with observations (see [10, 11]), it did not account for Advances in Astronomy some important effects, namely, the nonsphericity of grain shapes, the internal relaxation within grain, and the transient spinup due to ion collisions This induced more recent work in order to improve the original DL98 model.
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