Astrophysics of the Interstellar Medium

Preface
Contents
1 Fundamental Equations for Ideal Fluids
	1.1 Introduction: Fluids as Continuous Systems
	1.2 Continuity Equation
	1.3 Volume Forces and Surface Forces. Stresses
	1.4 Equation of Motion (Euler Equation) for Ideal Fluids
	1.5 Conservation of Total Energy and Thermal Energy
	1.6 Vorticity in Ideal Fluids. Potential Motion
	1.7 Numerical Solutions of Hydrodynamical Equations
	1.8 Synthetic Summary
2 Acoustic Waves
	2.1 Acoustic Waves in an Ideal Fluid at Rest
	2.2 Velocity of Propagation in a Dispersive Medium
	2.3 Acoustic Waves in a Patchy Medium at Rest
	2.4 Acoustic Waves in a Gravity-Dominated Medium
	2.5 Virial Theorem
	2.6 Gravitational Collapse of a Sphere
	2.7 Synthetic Summary
	References
3 Real Fluids
	3.1 Transport Phenomena
	3.2 Thermal Conduction
	3.3 Internal Friction
	3.4 Navier–Stokes Equation
	3.5 Energy Dissipation by Internal Friction
	3.6 Energy Balance in a Real Fluid
	3.7 Integration of Equations for a Real Fluid
	3.8 Case of Fluid with Low Viscosity
	3.9 Similar Motions
	3.10 Synthetic Summary
	References
4 The Interstellar Medium
	4.1 Thermal Balance of Interstellar Gas
	4.2 Thermodynamic State of Interstellar Gas
	4.3 Cooling Processes
	4.4 Heating Processes
	4.5 Thermal Instability
	4.6 Synthetic Summary
	References
5 Shock Waves
	5.1 Supersonic Motion and Discontinuity
	5.2 Jump Conditions
	5.3 Shock Waves
	5.4 Rankine–Hugoniot Conditions for an Ideal Gas
	5.5 Shock Waves in the Interstellar Medium
	5.6 Isothermal Shock: Schematic Discussion
	5.7 Structure of the Relaxation Layer
	5.8 Observability of Radiative Shocks
	5.9 Synthetic Summary
	Reference
6 Turbulence
	6.1 Experimental Aspects of Turbulence
	6.2 Stability of Stationary Motion and Turbulence Onset
	6.3 Notes on the Statistical Description of Turbulence
	6.4 General Characteristics of Turbulence
	6.5 Kolmogorov\'s Theory
	6.6 Turbulence of the Interstellar Medium
	6.7 Synthetic Summary
	References
7 Electrodynamics and Magnetohydrodynamics
	7.1 Plasmas. Debye Screening Length
	7.2 Plasma Oscillations
	7.3 A Note on Systems of Measurement Units
	7.4 Maxwell\'s Equations
	7.5 Magnetic Field Equation
	7.6 Freezing of the Magnetic Field Lines of Force
	7.7 The Galactic Magnetic Field: Origin and Methods of Measure
	7.8 Synthetic Summary
8 Motion of a Plasma in a Magnetic Field
	8.1 Expressions of Magnetic Force
	8.2 Fundamental Equations of Magnetohydrodynamics
	8.3 Motion of a Plasma with Respect to Magnetic Lines of Force
	8.4 Virial Theorem
	8.5 Application of the Virial Theorem
	8.6 Ambipolar Diffusion
	8.7 Synthetic Summary
9 Magnetohydrodynamic Waves
	9.1 Classification of MHD Waves
	9.2 Alfven Waves
	9.3 MHD Waves: General Discussion
	9.4 MHD Waves with Generic Propagation Direction
	9.5 Waves with Particular Direction of Propagation
	9.6 Alfven Waves Attenuation
	9.7 Excitation of MHD Waves
	9.8 Magnetohydrodynamic Shock Waves
	9.9 Synthetic Summary
10 Dust from the Interstellar Medium
	10.1 Introduction
	10.2 The Extinction of Radiation
	10.3 Observational Determination of Stellar Extinction
	10.4 The Extinction Curve of the Diffuse Medium in the Galaxy
	10.5 Methods for Determining  RV
	10.6 The Equilibrium Temperature of the Grains
	10.7 The Temperature of the Small Grains
	10.8 IR Emission of Galaxies
	10.9 Synthetic Summary
11 HII Regions
	11.1 Introduction
	11.2 Ionisation Balance
	11.3 Energy Balance and Temperature of an HII Region
	11.4 The Strömgren Sphere
	11.5 Effect of Dust on the HII Region
	11.6 Evolution of the HII Region in a Homogeneous Medium
	11.7 Classification of Ionization Fronts
	11.8 HII Region Expansion
	11.9 End of Expansion
	11.10 Expansion of an HII Region in an In-Homogeneous Medium
	11.11 Radio Frequency Emission
	11.12 Infrared Emission
	11.13 Calculation of the Lines of the Balmer Series
	11.14 HII Regions Excited by a Cluster
	11.15 Synthetic Summary
	Reference
12 Stellar Winds
	12.1 Introduction
	12.2 Classification of Winds
	12.3 Structure and Evolution of a Bubble Produced by a Strong Wind
	12.4 A Simplified Model for the Radiative Phase
	12.5 Evolution in Phase D
	12.6 Observations of the Bubbles
	12.7 Evolution of the Bubble in an In-Homogeneous Medium
	12.8 Synthetic Summary
	References
13 Supernovae Remnants
	13.1 Supernovae
	13.2 SNR Evolution
		13.2.1 Expansion End
	13.3 Expansion of a SNR in a Patchy Medium
		13.3.1 Magnetic Field
		13.3.2 Relativistic Particles
		13.3.3 Spherical Symmetry
	13.4 Models of Evolution in a Patchy Medium
	13.5 Effects of a SNR on the Interstellar Medium
	13.6 Superbubbles and Supershells
	13.7 Description of some SNRs
	13.8 Synthetic Summary
	References
14 The Interstellar Medium and Its Components
	14.1 The Structure of the Interstellar Medium
	14.2 Neutral Gas Diagnostic Techniques: The Line at 21 cm
	14.3 The Spiral Structure of the Milky Way
	14.4 Ionized Gas Diagnostic Techniques
		14.4.1 Dispersion of Pulsar Signals
		14.4.2 Recombination Optical Emission
		14.4.3 Absorption at Low Radio Frequencies
	14.5 The Hot Component: Coronal Gas
	14.6 The Cold Neutral Component: The Clouds of HI.
	14.7 The Warm Neutral Component
	14.8 Synthetic Summary
	References
15 Molecular Clouds
	15.1 Detection of Molecular Gas
	15.2 Correlation Between CO Emission and Molecular Gas Mass
	15.3 The Distribution of H2 in the Galaxy
	15.4 Distribution of H2 in Other Galaxies
	15.5 Clouds Classification and Statistical Properties
	15.6 Mechanical Equilibrium of Molecular Clouds
	15.7 Why the Clouds Where Stars Form Are Molecular?
	15.8 Mechanisms of Molecular Cloud Formation
		15.8.1 Formation of Clouds by the Compression of Ambient Gas Induced by Shock Waves
		15.8.2 Cloud Formation by Agglomeration of Smaller Clouds.
		15.8.3 Cloud Formation Through Medium Instability
		15.8.4 Summary
	15.9 Synthetic Summary
	References
16 Star Formation
	16.1 Observational Data Related to Star Formation
	16.2 Star Formation in the Presence of a Magnetic Field
	16.3 The formation of Low-Mass Stars
	16.4 Low-Mass Star Formation Scenario
	16.5 Observational Findings
	16.6 Synthetic Summary