DUST IN THE GALACTIC ENVIRONMENT
CONTENTS DUST IN THE GALAXY: OUR VIEW FROM WITHIN INTRODUCTION HISTORICAL PERSPECTIVE: DISCOVERY AND ASSIMILATION THE DISTRIBUTION OF DUST AND GAS OVERVIEW THE GALACTIC DISC HIGH GALACTIC LATITUDES DIFFUSE GALACTIC BACKGROUND RADIATION INTERSTELLAR ENVIRONMENTS AND PHYSICAL PROCESSES THE PHYSICAL STATE OF THE INTERSTELLAR MEDIUM INTERSTELLAR CLOUDS H II REGIONS THE INTERSTELLAR ENVIRONMENT OF THE SOLAR SYSTEM THE SIGNI?CANCE OF DUST IN MODERN ASTROPHYSICS FROM CINDERELLA TO THE SEARCH FOR ORIGINS INTERSTELLAR PROCESSES AND CHEMISTRY STARS, NEBULAE AND GALAXIES BACK TO BASICS A BRIEF HISTORY OF MODELS FOR INTERSTELLAR DUST DIRTY ICES, METALS AND PLATT PARTICLES GRAPHITE AND SILICATES UNMANTLED REFRACTORY AND CORE/MANTLE MODELS BIOTA RECOMMENDED READING PROBLEMS ABUNDANCES AND DEPLETIONS THE ORIGINS OF THE CONDENSIBLE ELEMENTS THE COSMIC CYCLE: AN OVERVIEW NUCLEOGENESIS STELLAR NUCLEOSYNTHESIS ENRICHMENT OF THE INTERSTELLAR MEDIUM THE SOLAR SYSTEM ABUNDANCES SIGNI?CANCE AND METHODOLOGY RESULTS ABUNDANCE TRENDS IN THE GALAXY TEMPORAL VARIATION SPATIAL VARIATION SOLAR ABUNDANCES IN SPACE AND TIME THE OBSERVED DEPLETIONS METHODS AVERAGE DEPLETIONS IN DIFFUSE CLOUDS DEPENDENCE ON ENVIRONMENT IMPLICATIONS FOR GRAIN MODELS EXTINCTION AND SCATTERING THEORETICAL METHODS EXTINCTION BY SPHERICAL PARTICLES SMALL-PARTICLE APPROXIMATIONS ALBEDO, SCATTERING FUNCTION AND ASYMMETRY PARAMETER COMPOSITE GRAINS OBSERVATIONAL TECHNIQUE THE AVERAGE EXTINCTION CURVE AND ALBEDO THE AVERAGE EXTINCTION CURVE SCATTERING CHARACTERISTICS LONG-WAVELENGTH EXTINCTION AND EVALUATION OF RV NEUTRAL EXTINCTION DUST DENSITY AND DUST-TO-GAS RATIO SPATIAL VARIATIONS THE BLUE–ULTRAVIOLET THE RED–INFRARED ORDER FROM CHAOS? THE 2175 ?A ABSORPTION FEATURE OBSERVED PROPERTIES IMPLICATIONS FOR THE IDENTITY OF THE CARRIER STRUCTURE IN THE VISIBLE MODELLING THE INTERSTELLAR EXTINCTION CURVE POLARIZATION AND GRAIN ALIGNMENT EXTINCTION BY ANISOTROPIC PARTICLES POLARIMETRY AND THE STRUCTURE OF THE GALACTIC MAGNETIC ?ELD BASICS MACROSCOPIC STRUCTURE POLARIZATION EF?CIENCY SMALL-SCALE STRUCTURE DENSE CLOUDS AND THE SKIN-DEPTH EFFECT THE SPECTRAL DEPENDENCE OF POLARIZATION THE SERKOWSKI LAW POWER-LAW BEHAVIOUR IN THE INFRARED POLARIZATION AND EXTINCTION REGIONAL VARIATIONS CIRCULAR POLARIZATION POLARIZATION AND GRAIN MODELS ALIGNMENT MECHANISMS GRAIN SPIN AND ROTATIONAL DISSIPATION PARAMAGNETIC RELAXATION: THE DG MECHANISM SUPERPARAMAGNETIC ALIGNMENT SUPRATHERMAL SPIN RADIATIVE TORQUES MECHANICAL ALIGNMENT ALIGNMENT IN DENSE CLOUDS INFRARED ABSORPTION FEATURES BASICS OF INFRARED SPECTROSCOPY VIBRATIONAL MODES IN SOLIDS INTRINSIC STRENGTHS OBSERVATIONAL APPROACH THE DIFFUSE ISM THE SPECTRA SILICATES SILICON CARBIDE HYDROCARBONS AND ORGANIC RESIDUES THE DENSE ISM AN INVENTORY OF ICES THE THRESHOLD EFFECT H2O-ICE: THE 3 µM PRO?LE SOLID CO: POLAR AND APOLAR MANTLES OTHER CARBON-BEARING ICES NITROGEN AND SULPHUR-BEARING ICES REFRACTORY DUST SPECTROPOLARIMETRY AND ALIGNMENT OF CORE–MANTLE GRAINS CONTINUUM AND LINE EMISSION THEORETICAL CONSIDERATIONS EQUILIBRIUM DUST TEMPERATURES FIR CONTINUUM EMISSION FROM AN INTERSTELLAR CLOUD EFFECT OF GRAIN SHAPE EFFECT OF GRAIN SIZE GALACTIC CONTINUUM EMISSION MORPHOLOGY SPECTRAL ENERGY DISTRIBUTION DUST AND GAS THE ‘COLD DUST PROBLEM’ SPECTRAL EMISSION FEATURES POLYCYCLIC AROMATIC HYDROCARBONS EXTENDED RED EMISSION DUST IN STELLAR EJECTA THE FORMATION OF DUST IN STELLAR OUT?OWS THE CIRCUMSTELLAR ENVIRONMENT O-RICH STARS CARBON STARS LATE STAGES OF STELLAR EVOLUTION OBSERVATIONAL CONSTRAINTS ON STARDUST INFRARED CONTINUUM EMISSION INFRARED SPECTRAL FEATURES CIRCUMSTELLAR EXTINCTION STARDUST IN METEORITES EVOLVED STARS AS SOURCES OF INTERSTELLAR GRAINS MASS-LOSS GRAIN-SIZE DISTRIBUTION DUST-TO-GAS RATIO COMPOSITION INJECTION RATE EVOLUTION IN THE INTERSTELLAR MEDIUM GRAIN SURFACE REACTIONS AND THE ORIGIN OF MOLECULAR HYDROGEN GAS-PHASE CHEMISTRY MECHANISMS FOR GROWTH COAGULATION MANTLE GROWTH ICE MANTLES: DEPOSITION AND EVOLUTION SURFACE CHEMISTRY AND HIERARCHICAL GROWTH DEPLETION TIMESCALES AND LIMITS TO GROWTH THERMAL AND RADIATIVE PROCESSING DESTRUCTION SIZE DISTRIBUTION METAMORPHOSIS DUST IN GALACTIC NUCLEI DUST IN THE ENVELOPES OF YOUNG STARS THE EARLY PHASES OF STELLAR EVOLUTION INFRARED EMISSION FROM DUSTY ENVELOPES POLARIZATION AND SCATTERING ICE SUBLIMATION IN HOT CORES PROTOPLANETARY DISCS T TAURI DISCS VEGA DISCS THE SOLAR NEBULA CLUES FROM THE EARLY SOLAR SYSTEM COMETS INTERPLANETARY DUST METEORITES INGREDIENTS FOR LIFE MOTIVATION THE DEUTERIUM DIAGNOSTIC AMINO ACIDS AND CHIRALITY DID LIFE START WITH RNA? DELIVERY TO EARTH 10 TOWARD A UNI?ED MODEL FOR INTERSTELLAR DUST 10 1 AREAS OF CONSENSUS 10 1 1 A GENERIC GRAIN MODEL 10 1 2 SILICATES 10 1 3 CARBON 10 1 4 ICES 10 1 5 ALIGNMENT 10 2 OPEN QUESTIONS REFERENCES CHAPTER INTRODUCTION INTERSTELLAR SPACE IS, BY TERRESTRIAL STANDARDS, A NEAR-PERFECT VACUUM: THE AVERAGE PARTICLE DENSITY IN THE SOLAR NEIGHBOURHOOD OF OUR GALAXY IS APPROXIMATELY 106 M?3 (ONE ATOM PER CUBIC CENTIMETRE), A FACTOR OF ABOUT 1019 LESS THAN IN THE TERRESTRIAL ATMOSPHERE AT SEA LEVEL HOWEVER, DENSE OBJECTS SUCH AS STARS AND PLANETS OCCUPY A TINY FRACTION OF THE TOTAL VOLUME OF THE GALAXY AND THE TENUOUS INTERSTELLAR MEDIUM1 CONTRIBUTES ROUGHLY A ?FTH OF THE MASS OF THE GALACTIC DISC THE STELLAR AND INTERSTELLAR COMPONENTS ARE CONTINUALLY INTERACTING AND EXCHANGING MATERIAL NEW STARS CONDENSE FROM INTERSTELLAR CLOUDS AND, AS THEY EVOLVE, THEY BATHE THE SURROUNDING ISM WITH RADIATION; ULTIMATELY, MANY STARS RETURN A SUBSTANTIAL FRACTION OF THEIR MASS TO THE ISM, WHICH IS THUS CONTINUOUSLY ENRICHED WITH HEAVIER ELEMENTS FUSED FROM THE PRIMORDIAL HYDROGEN AND HELIUM BY NUCLEAR PROCESSES OCCURRING IN STARS A MAJOR PROPORTION OF THESE HEAVIER ATOMS ARE LOCKED UP IN SUBMICRON-SIZED SOLID PARTICLES (DUST GRAINS), WHICH ACCOUNT FOR ROUGHLY 1% OF THE MASS OF THE ISM AND ARE ALMOST EXCLUSIVELY RESPONSIBLE FOR ITS OBSCURING EFFECT AT VISIBLE WAVELENGTHS DESPITE THEIR RELATIVELY SMALL CONTRIBUTION TO THE TOTAL MASS, THE REMARKABLE EF?CIENCY WITH WHICH SUCH PARTICLES SCATTER, ABSORB AND RE-RADIATE STARLIGHT ENSURES THAT THEY HAVE A VERY SIGNI?CANT IMPACT ON OUR VIEW OF THE UNIVERSE FOR EXAMPLE, THE ATTENUATION BETWEEN US AND THE 1 FOR CONVENIENCE, THE TERM ‘INTERSTELLAR MEDIUM’ (ISM) IS USED TO REFER, COLLECTIVELY, TO INTERSTELLAR MATTER OVER ALL LEVELS OF DENSITY, EMBRACING A WIDE RANGE OF ENVIRONMENTS (SECTION 1 4)