Magnetic Dipole Emission from Magnetic Grain Materials

If interstellar grains contain magnetic materials, thermal fluctuations in the magnetization will result in magnetic dipole emission (Draine & Lazarian 1999a). The predicted emission is shown in Figure 1 for various assumptions: 100% of the Fe in paramagnetic amorphous silicate mineral; 100% of the Fe locked up in magnetite (Fe₃O₄); or 5% of the Fe present in small metallic iron particles, either bare ellipsoids or inclusions within silicate grains.

Also shown are observational data points for microwave emission correlated with 100$\mu$m thermal emission from interstellar dust, in terms of microwave emissivity per H nucleon (see Draine & Lazarian 1999a,b).

 

Figure 1: Emissivity per H atom due to magnetic dipole emission from possible magnetic grain materials, plus the low-frequency tail of the ``vibrational emission'' from the overall grain population, for an assumed emissivity $Q_\nu\propto\nu^{1.7}$. See Draine & Lazarian (1999b)  

References

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• Draine, B.T., & Lazarian, A. 1999a, Astrophys. J., 512, 740-754.
• Draine, B.T., & Lazarian, A. 1999b, in Microwave Foregrounds, ed. A. de Oliveira-Costa & M. Tegmark (San Francisco: Astr. Soc. Pacific)].
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