Radiative torques on interstellar grains. II. Grain alignment

B. T. Draine, Joseph C. Weingartner

Research output: Contribution to journalArticlepeer-review

146 Scopus citations

Abstract

Radiative torques on irregular dust grains, in addition to producing superthermal rotation, play a direct dynamical role in the alignment of interstellar dust with the local magnetic field. The equations governing the orientation of spinning, precessing grains are derived; H2 formation torques and paramagnetic dissipation are included in the dynamics. Stationary solutions (constant alignment angle and spin rate) are found; these solutions may be stable ("attractors") or unstable ("repellors"). The equations of motion are numerically integrated for three exemplary irregular grain geometries, exposed to anisotropic radiation with the spectrum of interstellar starlight. The resulting "trajectory maps" are classified as " noncyclic," " semicyclic," or " cyclic," with examples of each given. We find that radiative torques result in rapid grain alignment, even in the absence of paramagnetic dissipation. It appears that radiative torques due to starlight can account for the observed alignment of interstellar grains with the Galactic magnetic field.

Original languageEnglish (US)
Pages (from-to)633-646
Number of pages14
JournalAstrophysical Journal
Volume480
Issue number2 PART I
DOIs
StatePublished - 1997

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • ISM: dust, extinction
  • Polarization
  • Scattering

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