ARlogo Annu. Rev. Astron. Astrophys. 1991. 29: 581-625
Copyright © 1991 by Annual Reviews. All rights reserved

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10. CONCLUSIONS

The explosive growth of molecular line observations (primarily CO) in galaxies over the last decade have provided a detailed characterization of the dense interstellar medium and its relationship to star formation in galaxies. The total H2 content of approximately 400 galaxies has now been determined, and characterizations of the H2, H2 / HI, Lstar / H2, and gas mass fraction as a function of morphological type, galactic luminosity, and environment are becoming well established. In addition, high resolution studies in recent years have at last provided the spatial resolution to define the role of molecular gas in spiral structure and starburst galactic nuclei.

Major advances are anticipated for the next decade from radically improved instrumental capabilities. The very large aperture single dish telescope will enable detection of CO emission from gas-rich galaxies out to z ~ 1 and perhaps enable detection of true protogalactic objects. The greatly increased speed and sensitivity expected for millimeter-wave aperture synthesis arrays should provide a similar explosive increase in high resolution imaging of galaxies. The order of magnitude increase in speed expected for focal plane arrays in conjunction with single dish telescopes will provide the unique capability of imaging large, nearby galaxies. Lastly, observations at submillimeter wavelengths will enable more detailed analysis of the physical conditions in the molecular gas from multitransition studies and high resolution observations of the far infrared continuum.

ACKNOWLEDGMENTS

It is a pleasure to acknowledge the extensive work of Leona Kershaw in preparation of this manuscript. The authors wish to thank Drs. Nick Devereux and Dave Sanders for helpful discussions. This work is supported in part by NSF Grants AST 88-15406 (J.Y.) and AST 87-14405 (N.S.). J.Y. also wishes to thank the JCMT and University of Hawaii for generous support during the completion of this manuscript.

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