Evolution of the Stars and Gas in Galaxies

1. Overview 1.1 Stellar populations and chemical compositions of galaxies 1.2 Galaxy formation and evolution 1.3 Plan of this review 2. The Formation and Evolution of Stars 2.1 Basic physical properties of stars 2.2 The initial mass function 2.2.1 The local IMF 2.2.2 The IMF at other times and places 2.3 Rates of star formation 2.3.1 The local SFR 2.3.2 The SFR elsewhere 2.3.3 Factors affecting the SFR 2.4 Stellar evolution beyond the main sequence 2.4.1 Stars near solar mass 2.4.2 Stars of 1-4 M? 2.4.3 Stars above 8 M? 2.4.4 Stars of intermediate mass 2.4.5 Effects of initial composition 3. Aims and Methods of Chemical Evolution 3.1 Basic assumptions and equations 3.2 Analytical approximations 3.2.1 A closed system, initially unenriched gas 3.2.2 A system with infall balanced by star formation 3.2.3 Generalities 3.3 Numerical models 4. Chemical Evolution in the Solar Neighborhood 4.1 Outline of relevant data 4.2 The "G-dwarf problem" 4.2.1 Infall 4.2.2 Pre-enrichment of the disk gas 4.2.3 Variable IMF 4.2.4 Metal-enhanced star formation 4.3 Effects of galaxy formation 4.3.1 Metals from the young halo 4.3.2 Later metal-poor infall 4.3.3 Time scales for chemical evolution 4.4 Relative abundances of the elements 4.4.1 Primary elements from different stars 4.4.2 Secondary elements 4.4.3 Radioactive elements 5. Chemical Evolution of Galaxies 5.1 Outline of relevant data 5.2 Abundance gradients in spheroidal systems 5.2.1 Dissipative collapse 5.2.2 A gradient in the IMF 5.2.3 Finite stellar lifetimes 5.3 The metallicity-mass relation for elliptical galaxies 5.3.1 Supernova-driven winds 5.3.2 Bursts of star formation in merging subsystems 5.3.3 Mergers of stellar systems 5.4 The intergalactic medium and gas loss from galaxies 5.4.1 Loss of metals from galaxies 5.4.2 Overall gas loss from galaxies 5.4.3 Ejection from evolving stars in elliptical galaxies 5.5 Abundance gradients in disks 5.5.1 Effects of infall 5.5.2 Effects of radial gas flows 6. Approaches to Photometric Evolution 6.1 Aims and methods 6.1.1 Population synthesis 6.1.2 Evolutionary models 6.1.3 Analytical approximations 6.2 Evolution of a single generation of stars 6.2.1 Content and luminosity 6.2.2 Remnants of dead stars 6.2.3 The ratio of giants to dwarfs in the light 6.2.4 The stellar mass loss rate relative to luminosity 6.2.5 The mass-to-luminosity ratio 6.2.6 Evolution of luminosity and the Hubble diagram 6.2.7 Evolution of colors 7. Colors and Star Formation Rates 7.1 UBV colors of normal galaxies 7.1.1 "Standard" models 7.1.2 Possible effects of errors 7.1.3 Variations in age 7.1.4 Variations in metallicity 7.1.5 Variations in the IMF 7.1.6 Relevance to the formation and structure of normal galaxies 7.2 Colors of peculiar galaxies 7.2.1 Bursts of star formation and blue colors 7.2.2 Highly reddened galaxies 8. Conclusion