Endrik Krugel

The Physics of Interstellar Dust (eBook, ePUB)

• Format: ePub

Produktbeschreibung

Interstellar dust clouds catalyze simple chemical reactions, absorb, scatter, polarize, and re-radiate starlight, and form the building blocks for planet and stellar formation. Understanding this interstellar medium is then of primary importance in many areas of astronomy & astrophysics. This book provides a theoretical description of the fundamental physics of interstellar material, including a description of its composition, morphology, grain size and distribution, dynamics, dielectric permeability, radiation scattering and spectral features. Other chapters describe the surface chemistry, and role of dust in stellar formation, including the spectral behavior of protostars and dust around early stars.

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Produktdetails

• Verlag: Taylor & Francis
• Seitenzahl: 560
• Erscheinungstermin: 2. Dezember 2002
• Englisch
• ISBN-13: 9781000687521
• Artikelnr.: 57530840

Autorenporträt

Endrik Krügel Max-Planck-Institut für Radioastronomie, Bonn, Germany

Inhaltsangabe

Preface
1 The dielectric permeability
1.1 Maxwell's equations
1.1.1 Electric field and magnetic induction
1.1.2 Electric polarization of the medium
1.1.3 The dependence of the dielectric permeability on direction and frequency
1.1.4 The physical meaning of the electric susceptibility x
1.1.5 Magnetic polarization of the medium
1.1.6 The magnetic susceptibility
1.1.7 Dielectrics and metals
1.1.8 Free charges and polarization charges
1.1.9 The field equations
1.2 Waves in a dielectric medium
1.2.1 The wave equation
1.2.2 The wave number
1.2.3 The optical constant or refractive index
1.2.4 Energy dissipation of a grain in a variable field
1.3 The harmonic oscillator
1.3.1 The Lorentz model
1.3.2 Free oscillations
1.3.3 The general solution to the oscillator equation
1.3.4 Dissipation of energy in a forced oscillation
1.3.5 Dissipation of energy in a free oscillation
1.3.6 The plasma frequency
1.3.7 Dispersion relation of the dielectric permeability
1.4 The harmonic oscillator and light
1.4.1 Attenuation and refraction of light
1.4.2 Retarded potentials of a moving charge
1.4.3 Emission of an harmonic oscillator
1.4.4 Radiation of higher order
1.4.5 Radiation damping
1.4.6 The cross section of an harmonic oscillator
1.4.7 The oscillator strength
1.4.8 The natural line width
1.5 Waves in a conducting medium
1.5.1 The dielectric permeability of a conductor
1.5.2 Conductivity and the Drude profile
1.5.3 Electromagnetic waves in a plasma with a magnetic field
1.5.4 Group velocity of electromagnetic waves in a plasma
1.6 Polarization through orientation
1.6.1 Polarization in a constant field
1.6.2 Polarization in a time-variable field
1.6.3 Relaxation after switching off the field
1.6.4 The dielectric permeability in Debye relaxation
2 How to evaluate grain cross sections
2.1 Defining cross sections
2.1.1 Cross section for scattering
absorption and extinction
2.1.2 Cross section for radiation pressure
2.1.3 Efficiencies
mass and volume coefficients
2.2 The optical theorem
2.2.1 The intensity of forward scattered light
2.2.2 The refractive index of a dusty medium
2.3 Mie theory for a sphere
2.3.1 The generating function
2.3.2 Separation of variables
2.3.3 Series expansion of waves
2.3.4 Expansion coefficients
2.3.5 Scattered and absorbed power
2.3.6 Absorption and scattering efficiencies
2.4 Polarization and scattering
2.4.1 The amplitude scattering matrix
2.4.2 Angle-dependence of scattering
2.4.3 The polarization ellipse
2.4.4 Stokes parameters
2.4.5 Stokes parameters of scattered light for a sphere
2.5 The Kramers-Kronig relations
2.5.1 Mathematical formulation of the relations
2.5.2 The electric susceptibility and causality
2.5.3 The Kramers-Kronig relation for the dielectric permeability
2.5.4 Extension to metals
2.5.5 Dispersion of the magnetic susceptibility
2.5.6 Three corollaries of the KK relation
2.6 Composite grains
2.6.1 Effective medium theories
2.6.2 Garnett's mixing rule
2.6.3 The mixing rule of Bruggeman
2.6.4 Composition of grains in protostellar cores
2.6.5 How size
ice and porosity change the absorption coefficient
3 Very small and very big particles
3.1 Tiny spheres
3.1.1 When is a particle in the Rayleigh limit?
3.1.2 Efficiencies of small spheres from Mie theory
3.1.3 A dielectric sphere in a constant electric field
3.1.4 Scattering and absorption in the electrostatic approximation
3.1.5 Polarization and angle-dependent scattering
3.1.6 Small-size effects beyond Mie theory
3.2 A small metallic sphere in a magnetic field
3.2.1 Slowly varying field
3.2.2 The magnetic polarizability
3.2.3 The penetration depth
3.2.4 Limiting values of the magnetic polarizability
3.3 Tiny ellipsoids
3.3.1 Elliptical coordinates
3.3.2 An ellipsoid in a constant electric field
3.3.3 Cross section and shape factor
3.3.4 Randomly oriented ellipsoids
3.3.5 Pancakes and cigars
3.3.6 Rotation about the axis of greatest moment of inertia
3.4 The fields inside a dielectric particle
3.4.1 Internal field and depolarization field
3.4.2 Depolarization field and the distribution of surface charges
3.4.3 The local field at an atom
3.4.4 The Clausius-Mossotti relation
3.5 Very large particles
3.5.1 Babinet's theorem
3.5.2 Reflection and transmission at a plane surface
3.5.3 Huygens' principle
3.5.4 Fresnel zones and a check on Huygens' principle
3.5.5 The reciprocity theorem
3.5.6 Diffraction by a circular hole or a sphere
3.5.7 Diffraction behind a half-plane
3.5.8 Particles of small refractive index
3.5.9 X-ray scattering
4 Case studies of Mie calculus
4.1 Efficiencies of bare spheres
4.1.1 Pure scattering
4.1.2 A weak absorber
4.1.3 A strong absorber
4.1.4 A metal sphere
4.1.5 Efficiency versus cross section and volume coefficient
4.1.6 The atmosphere of the Earth
4.2 Scattering by bare spheres
4.2.1 The scattering diagram
4.2.2 The polarization of scattered light
4.2.3 The intensity of scattered light in a reflection nebula
4.3 Coated spheres
4.4 Surface modes in small grains
4.5 Efficiencies of idealized dielectrics and metals
4.5.1 Dielectric sphere consisting of identical harmonic oscillators
4.5.2 Dielectric sphere with Debye relaxation
4.5.3 Magnetic and electric dipole absorption of small metal spheres
4.5.4 Efficiencies for Drude profiles
4.5.5 Elongated metallic particles
5 Particle statistics
5.1 Boltzmann statistics
5.1.1 The probability of an arbitrary energy distribution
5.1.2 The distribution of maximum probability
5.1.3 Partition function and population of energy cells
5.1.4 The mean energy of harmonic oscillators
5.1.5 The Maxwellian velocity distribution
5.2 Quantum statistics
5.2.1 The unit cell h3 of the phase space
5.2.2 Bosons and fermions
5.2.3 Bose statistics
5.2.4 Bose statistics for photons
5.2.5 Fermi statistics
5.2.6 Ionization equilibrium and the Saha equation
5.3 Thermodynamics
5.3.1 The ergodic hypothesis
5.3.2 Definition of entropy and temperature
5.3.3 The canonical distribution
5.3.4 Thermodynamic relations for a gas
5.3.5 Equilibrium conditions of the state functions
5.3.6 Specific heat of a gas
5.3.7 The work done by magnetization
5.3.8 Susceptibility and specific heat of magnetic substances
5.4 Blackbody radiation
5.4.1 The Planck function
5.4.2 Low- and high-frequency limit
5.4.3 Wien's displacement law and the Stefan-Boltzmann law
5.4.4 The Planck function and harmonic oscillators
6 The radiative transition probability
6.1 A charged particle in an electromagnetic field
6.1.1 The classical Hamiltonian
6.1.2 The Hamiltonian of an electron in an electromagnetic field
6.1.3 The Hamilton operator in quantum mechanics
6.1.4 The dipole moment in quantum mechanics
6.1.5 The quantized harmonic oscillator
6.2 Small perturbations
6.2.1 The perturbation energy
6.2.2 The transition probability
6.2.3 Transition probability for a time-variable perturbation
6.3 The Einstein coefficients A and B
6.3.1 Induced and spontaneous transitions
6.3.2 Selection rules and polarization rules
6.3.3 Quantization of the electromagnetic field
6.3.4 Quantum-mechanical derivation of A and B
6.4 Potential wells and tunneling
6.4.1 Wavefunction of a particle in a constant potential
6.4.2 Potential walls and Fermi energy
6.4.3 Rectangular potential barriers
6.4.4 The double potential well
7 Structure and composition of dust
7.1 Crystal structure
7.1.1 Translational symmetry
7.1.2 Lattice types
7.1.3 The reciprocal lattice
7.2 Binding in crystals
7.2.1 Covalent bonding
7.2.2 Ionic bonding
7.2.3 Metals
7.2.4 van der Waals forces and hydrogen bridges
7.3 Reddening by interstellar grains
7.3.1 Stellar photometry
7.3.2 The interstellar extinction curve
7.3.3 Two-color diagrams
7.3.4 Spectral indices
7.3.5 The mass absorption coefficient
7.4 Carbonaceous grains and silicate grains
7.4.1 Origin of the two major dust constituents
7.4.2 The bonding in carbon
7.4.3 Carbon compounds
7.4.4 Silicates
7.4.5 A standard set of optical constants
7.5 Grain sizes and optical constants
7.5.1 The size distribution
7.5.2 Collisional fragmentation
8 Dust radiation
8.1 Kirchhoff's law
8.1.1 The emissivity of dust
8.1.2 Thermal emission of grains
8.1.3 Absorption and emission in thermal equilibrium
8.1.4 Equipartition of energy
8.2 The temperature of big grains
8.2.1 The energy equation
8.2.2 Approximate absorption efficiency at infrared wavelengths
8.2.3 Temperature estimates
8.2.4 Relation between grain size and grain temperature
8.2.5 Temperature of dust grains near a star
8.2.6 Dust temperatures from observations
8.3 The emission spectrum of big grains
8.3.1 Constant temperature and low optical depth
8.3.2 Constant temperature and arbitrary optical depth
8.4 Calorific properties of solids
8.4.1 Normal coordinates
8.4.2 Internal energy of a grain
8.4.3 Standing waves in a crystal
8.4.4 The density of vibrational modes in a crystal
8.4.5 Specific heat
8.4.6 Two-dimensional lattices
8.5 Temperature fluctuations of very small grains
8.5.1 The probability density
8.5.2 The transition matrix
8.5.3 Practical considerations
8.5.4 The stochastic time evolution of grain temperature
8.6 The emission spectrum of very small grains
8.6.1 Small and moderate fluctuations
8.6.2 Strong fluctuations
8.6.3 Temperature fluctuations and flux ratios
9 Dust and its environment
9.1 Grain surfaces
9.1.1 Gas accretion on grains
9.1.2 Physical adsorption and chemisorption
9.1.3 The sticking probability
9.1.4 Thermal hopping
evaporation and reactions with activation barrier
9.1.5 Tunneling between surface sites
9.1.6 Scanning time
9.2 Grain charge
9.2.1 Charge equilibrium in the absence of a UV radiation field
9.2.2 The photoelectric effect
9.3 Grain motion
9.3.1 Random walk
9.3.2 The drag on a grain subjected to a constant outer force
9.3.3 Brownian motion of a grain
9.3.4 The disorder time
9.3.5 Laminar and turbulent friction
9.3.6 A falling rain drop
9.3.7 The Poynting-Robertson effect
9.4 Grain destruction
9.4.1 Mass balance in the Milky Way
9.4.2 Destruction processes
9.5 Grain formation
9.5.1 Evaporation temperature of dust
9.5.2 Vapor pressure of small grains
9.5.3 Critical saturation
9.5.4 Equations for time-dependent homogeneous nucleation
9.5.5 Equilibrium distribution and steady-state nucleation
9.5.6 Solutions to time-dependent homogeneous nucleation
9.5.7 Similarity relations
10 Polarization
10.1 Efficiency of infinite cylinders
10.1.1 Normal incidence and picket fence alignment
10.1.2 Oblique incidence
10.1.3 Rotating cylinders
10.1.4 Absorption efficiency as a function of wavelength
10.2 Linear polarization through extinction
10.2.1 Effective optical depth and degree of polarization p(.)
10.2.2 The Serkowski curve
10.2.3 Polarization p(.) of infinite cylinders
10.2.4 Polarization p(.) of ellipsoids in the Rayleigh limit
10.2.5 Polarization p(.) of spheroids at optical wavelengths
10.2.6 Polarization and reddening
10.3 Polarized emission
10.3.1 The wavelength dependence of polarized emission for cylinders
10.3.2 Infrared emission of spheroids
10.3.3 Polarized emission versus polarized extinction
10.4 Circular polarization
10.4.1 The phase shift induced by grains
10.4.2 The wavelength dependence of circular polarization
11 Grain alignment
11.1 Grain rotation
11.1.1 Euler's equations for a rotating body
11.1.2 Symmetric tops
11.1.3 Atomic magnet in a magnetic field
11.1.4 Rotational Brownian motion
11.1.5 Suprathermal rotation
11.2 Magnetic dissipation
11.2.1 Diamagnetism
11.2.2 Paramagnetism
11.2.3 Ferromagnetism
11.2.4 The magnetization of iron above and below the Curie point
11.2.5 Paramagnetic dissipation: spin-spin and spin-lattice relaxation
11.2.6 The magnetic susceptibility for spin-lattice relaxation
11.2.7 The magnetic susceptibility in spin-spin relaxation
11.3 Magnetic alignment
11.3.1 A rotating dipole in a magnetic field
11.3.2 Timescales for alignment and disorder
11.3.3 Super-paramagnetism
11.3.4 Ferromagnetic relaxation
11.3.5 Alignment of angular momentum with the axis of greatest inertia
11.3.6 Mechanical and magnetic damping
11.4 Non-magnetic alignment
11.4.1 Gas streaming
11.4.2 Anisotropic illumination
12 PAHs and spectral features of dust
12.1 Thermodynamics of PAHs
12.1.1 What are PAHs?
12.1.2 Microcanonic emission of PAHs
12.1.3 The vibrational modes of anthracene
12.1.4 Microcanonic versus thermal level population
12.1.5 Does an ensemble of PAHs have a temperature?
12.2 PAH emission
12.2.1 Photoexcitation of PAHs
12.2.2 Cutoff wavelength for electronic excitation
12.2.3 Photo-destruction and ionization
12.2.4 Cross sections and line profiles of PAHs
12.3 Big grains and ices
12.3.1 The silicate features and the band at 3.4 µm
12.3.2 Icy grain mantles
12.4 An overall dust model
12.4.1 The three dust components
12.4.2 Extinction coefficient in the diffuse medium
12.4.3 Extinction coefficient in protostellar cores
13 Radiative transport
13.1 Basic transfer relations
13.1.1 Radiative intensity and flux
13.1.2 The transfer equation and its formal solution
13.1.3 The brightness temperature
13.1.4 The main-beam-brightness temperature of a telescope
13.2 Spherical clouds
13.2.1 Moment equations for spheres
13.2.2 Frequency averages
13.2.3 Differential equations for the intensity
13.2.4 Integral equations for the intensity
13.2.5 Practical hints
13.3 Passive disks
13.3.1 Radiative transfer in a plane parallel layer
13.3.2 The grazing angle in an inflated disk
13.4 Galactic nuclei
13.4.1 Hot spots in a spherical stellar cluster
13.4.2 Low and high luminosity stars
13.5 Line radiation
13.5.1 Absorption coefficient and absorption profile
13.5.2 The excitation temperature of a line
13.5.3 Radiative transfer in lines
14 Diffuse matter in the Milky Way
14.1 Overview of the Milky Way
14.1.1 Global parameters
14.1.2 The relevance of dust
14.2 Molecular clouds
14.2.1 The CO molecule
14.2.2 Population of levels in CO
14.2.3 Molecular hydrogen
14.2.4 Formation of molecular hydrogen on dust surfaces
14.3 Clouds of atomic hydrogen
14.3.1 General properties of the diffuse gas
14.3.2 The 21 cm line of atomic hydrogen
14.3.3 How the hyperfine levels of atomic hydrogen are excited
14.3.4 Gas density and temperature from the 21 cm line
14.3.5 The deuterium hyperfine line
14.3.6 Electron density and magnetic field in the diffuse gas
14.4 HII regions
14.4.1 Ionization and recombination
14.4.2 Dust-free HII regions
14.4.3 Dusty HII regions
14.4.4 Bremsstrahlung
14.4.5 Recombination lines
14.5 Mass estimates of interstellar clouds
14.5.1 From optically thin CO lines
14.5.2 From the CO luminosity
14.5.3 From dust emission
15 Stars and their formatio
15.1 Stars on and beyond the main sequence
15.1.1 Nuclear burning and the creation of elements
15.1.2 The binding energy of an atomic nucleus
15.1.3 Hydrogen burning
15.1.4 The 3a process
15.1.5 Lifetime and luminosity of stars
15.1.6 The initial mass function
15.2 Clouds near gravitational equilibrium
15.2.1 Virialized clouds
15.2.2 Isothermal cloud in pressure equilibrium
15.2.3 Structure and stability of Ebert-Bonnor spheres
15.2.4 Free-fall of a gas ball
15.2.5 The critical mass for gravitational instability
15.2.6 Implications of the Jeans criterion
15.2.7 Magnetic fields and ambipolar diffusion
15.3 Gravitational collapse
15.3.1 The presolar nebula
15.3.2 Hydrodynamic collapse simulations
15.3.3 Similarity solutions of collapse
15.4 Disks
15.4.1 Viscous laminar flows
15.4.2 Dynamical equations of the thin accretion disk
15.4.3 The Kepler disk
15.4.4 Why a star accretes from a disk
15.4.5 The stationary accretion disk
15.4.6 The a-disk
15.4.7 Disk heating by viscosity
16 Emission from young star
16.1 The earliest stages of star formation
16.1.1 Globules
16.1.2 Isothermal gravitationally-bound clumps
16.2 The collapse phase
16.2.1 The density structure of a protostar
16.2.2 Dust emission from a solar-type protostar
16.2.3 Kinematics of protostellar collapse
16.3 Accretion disks
16.3.1 A flat blackbody disk
16.3.2 A flat non-blackbody disk
16.3.3 Radiative transfer in an inflated disk
16.4 Reflection nebulae
16.5 Cold and warm dust in galaxies
16.6 Starburst nuclei
16.6.1 Repetitive bursts of star formation
16.6.2 Dust emission from starburst nuclei
Appendix A Mathematical formulae
Appendix B List of symbols
References
Index