To appear in "Carnegie Observatories Astrophysics Series, Vol. 4: Origin and Distribution of the Elements", ed. A. McWilliam and M. Rauch (Cambridge: Cambridge Univ. Press) (2004)
astro-ph/0312592

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INTERSTELLAR DUST

B. T. Draine


Princeton University Observatory


Abstract. In the interstellar medium of the Milky Way, certain elements - e.g., Mg, Si, Al, Ca, Ti, Fe - reside predominantly in interstellar dust grains. These grains absorb, scatter, and emit electromagnetic radiation, heat the interstellar medium by photoelectric emission, play a role in the ionization balance of the gas, and catalyze the formation of molecules, particularly H2. I review the state of our knowledge of the composition and sizes of interstellar grains, including what we can learn from spectral features, luminescence, scattering, infrared emission, and observed gas-phase depletions. The total grain volume in dust models which reproduce interstellar extinction is significantly greater than estimated from observed depletions.

Dust grains might reduce the gas-phase D/H ratio, providing an alternative mechanism to explain observed variations in the gas-phase D/H ratio in the local interstellar medium. Transport in dust grains could cause elemental abundances in newly-formed stars to differ from interstellar abundances.


Table of Contents

INTRODUCTION

PRESOLAR GRAINS IN METEORITES ARE NONREPRESENTATIVE

INTERSTELLAR REDDENING

SPECTROSCOPY OF DUST IN EXTINCTION AND EMISSION
PAH Emission Features
2175Å Feature: Graphitic C
10 and 18 µm Silicate Features
3.4 µm C-H Stretch: Aliphatic Hydrocarbons
Diffuse Interstellar Bands
Extended Red Emission
X-Ray Absorption Edges

INFRARED EMISSION SPECTRUM OF INTERSTELLAR DUST

DUST GRAIN SIZE DISTRIBUTION

DUST ABUNDANCES VS. DEPLETION PATTERNS

TIME SCALE FOR DEPLETION

LOCAL VARIATIONS IN D/H: DOES DUST PLAY A ROLE?

TRANSPORT OF ELEMENTS IN DUST GRAINS
Anisotropic Starlight
Star-Forming Regions

ION RECOMBINATION ON DUST GRAINS

SUMMARY

REFERENCES

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