The submillimeter and millimeter excess of the small magellanic cloud: Magnetic dipole emission from magnetic nanoparticles?

B. T. Draine, Brandon Hensley

Research output: Contribution to journalArticle

58 Scopus citations

Abstract

The Small Magellanic Cloud (SMC) has surprisingly strong submillimeter- and millimeter-wavelength emission that is inconsistent with standard dust models, including those with emission from spinning dust. Here, we show that the emission from the SMC may be understood if the interstellar dust mixture includes magnetic nanoparticles, emitting magnetic dipole radiation resulting from thermal fluctuations in the magnetization. The magnetic grains can be metallic iron, magnetite Fe3O4, or maghemite γ-Fe2O3. The required mass of iron is consistent with elemental abundance constraints. The magnetic dipole emission is predicted to be polarized orthogonally to the normal electric dipole radiation if the nanoparticles are inclusions in larger grains. We speculate that other low-metallicity galaxies may also have a large fraction of the interstellar Fe in magnetic materials.

Original languageEnglish (US)
Article number103
JournalAstrophysical Journal
Volume757
Issue number1
DOIs
StatePublished - Sep 20 2012

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Magellanic Clouds
  • dust, extinction
  • infrared: ISM
  • infrared: galaxies
  • polarization
  • radiation mechanisms: thermal
  • radio continuum: ISM

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