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Article Contents

ABSTRACT

1.MOTIVATION AND OUTLINE

2.THE COMPLEX STRUCTURE OF THE ISM IN GALAXY DISKS
- Five Gas Phases
- Additional Components of the ISM

3.KEY OBSERVATIONS OF THE GALACTIC ISM
- The Molecular Medium (MM)
- The Cold Neutral Medium (CNM)
- The Warm Neutral Medium (WNM)
- The Warm Ionized Medium (WIM)
- The Hot Ionized Medium (HIM)
- Observations of Dust
- Observations of Cosmic Rays and Magnetic Fields

4.THE ISM IN THE MILKY WAY HALO
- The H I in the Halo
- Warm and Hot Ionized Gas in the Galaxy
- The Galactic "Cirrus"
- Cosmic Rays and B fields
- Signs of Ongoimg Disk-Halo Interactions

5.STAR FORMATION IN LATE-TYPE SPIRAL GALAXIES
- Starburst vs. Normal Galaxies

6.GASEOUS HALOS OF EXTERNAL SPIRAL GALAXIES - MULTI - FREQUENCY OBSERVATIONS
- Edge-On Starburst Galaxies
- Edge-On Normal Spiral Galaxies
- Galaxies with both Starburst and Widespread SF
- Starbursts and Active Galactic Nuclei
- Irregular Galaxies
- Quasar Absorption Line Studies
- Disk-Halo Interactions in Face-On Galaxies

7.THE OVERALL OBSERVATIONAL PICTURE
- Which Spiral Galaxies Have Halos?

8.THEORETICAL MODELS OF THE ISM IN GALAXIES
- First Generation (Static) Models
- More Refined (Dynamic) Models
- Current Models
- Heating Processes and Total Energy Balance
- Energy Scale and Size Scales
- Environmental Influences
- Temporal Variations

9.SUMMARY

REFERENCES