Interstellar Astrochemistry

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

With this award, Dr. Eric Herbst will continue a program in astrochemistry, which is the study of the role of molecules in the universe, where they are found, how they are created and destroyed, and what they tell us about the myriad of different sources in our galaxy and others. In particular he is especially interested in what information observations of molecules yield about the process of star formation. Much of what we know about the interstellar medium is learned by observations of molecular spectra, which can be analyzed to determine molecular abundances. Yet what do these abundances signify? In order to understand fully what molecules are telling us about the present and past of the objects in which they reside, it is necessary to comprehend how the molecules are formed and destroyed, and how these formation and destruction processes depend on physical conditions such as temperature and density as well as the history of the sources. To understand molecular creation and depletion, large networks of chemical reactions have been created, including both gas phase and grain-surface processes. Used with physical models of sources, either homogeneous or heterogeneous, these chemical networks allow the modeler to calculate molecular abundances, both in the gas and on the surfaces of dust grains. Successful comparison with observational data then gives us information on physical conditions and lifetimes of sources. The studies in this project build on earlier work from the laboratory, and are mainly concerned with the process of star formation, which leads to a large variety of different manifestations and stages. Through the study of molecular spectra, as analyzed through the prism of chemical calculations, one can begin to glimpse what is happening to gas and dust as stars form. Dr. Herbst's work in astrochemistry has been instrumental in the burgeoning use of molecules as probes of the interstellar medium. From its beginnings in the late 60s and early 70s, the field of molecular astronomy has become a world-wide endeavor in which observational astronomers, theoretical chemists, experimental scientists, and modelers collaborate on problems of mutual interest. Much of the knowledge of diffuse and dense interstellar clouds, and especially star formation, now comes from an understanding of what molecules in these regions are telling us. Moreover, the study of the synthesis of complex molecules in interstellar clouds is an interesting field on its own and is clearly relevant to the development of biology. In addition to continuing a research program in astrochemistry, Dr. Herbst has tried to make the field known to both scientists in other fields and to the lay public by publishing review articles, giving interviews for magazines and newspapers, and by going to local elementary, middle, and high schools to discuss the molecular universe. In the last year, The Ohio State University has created a special interdisciplinary Program in Astrochemistry to be headed by Dr. Herbst, and he will run a mini-conference on astrochemistry each June as part of the larger spectroscopy symposium held in Columbus, Ohio. ***