The Dense Interstellar Medium in Dwarf Galaxies

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AST 98-03065 James M. Jackson Dr. Jackson and Dr. Bania are observing three galaxies that belong to the Milky Way Local Group of galaxies: the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), and IC 10. The Local Group has about 30 member galaxies in it. The Milky Way and the Andromeda Galaxy are the two large galaxy members of the Local Group. The other galaxies are dwarf ellipticals or irregulars. The LMC and the SMC are two irregular galaxies that show evidence of a past interaction with the Milky Way. The galaxy IC 10 is a nearby dwarf elliptical galaxy. The LMC and SMC are southern hemisphere objects. IC 10 is a northern hemisphere galaxy. Dwarf galaxies such as these three form useful analogs to the conditions found in early galaxies. Early galaxies have low metallicities as well as star forming regions, just as the dwarfs do. Dwarf galaxies have the advantage that many are relatively close. The PI's can, therefore, use these observations from nearby dwarf galaxies to build a template to use for primordial star formation (PSF) studies. Dense molecular gas is a crucial element in the formation of stars. This gas provides the raw fuel for new star formation. Such dense gas has been difficult to observe in the past and only the brightest of the molecular lines had been measured. These lines are found in the submillimeter and millimeter part of the electromagnetic spectrum. Now with improved millimeter and submillimeter wavelength receivers and telescopes the PI's observe and map several new molecular emission lines, especially the mid J CO lines and the C I lines. The new Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is ideal for studies in the submillimeter part of the electromagnetic spectrum. This project is part of an Observatory Key Project to survey the Magellanic Clouds. The PI's also use the James Clark Maxwell Telescope (JCMT) for IC 10 which is a northern hemisphere galaxy. In addition, they use data from the Infrared Satellite Observatory (ISO) to complete a set of diagnostics. ***