Radio and Infrared Studies of Star Formation in Galaxies

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ABSTRACTAST- 0071276TurnerThe goal of this project is to obtain IR Brackett-line spectroscopy, 10-micron and 20-micron observations using the Keck telescope, and VLA synthesis images at 1 and 2cm for between 6 and 12 nearby galaxies which have bright radio continuum emission at 1 cm. These will be used to study the emission from star-forming regions in these objects. The data will provide a substantive base for the interpretation of future ground-based (the Atacama Large Millimeter Array and inferred observations from the South Pole) and deep, space-based (SOFIA/SIRTF ) surveys where the 10 micron region will be redshifted to100 microns.A dramatic mode of star formation is the starburst, in which star formation appears to proceed via large clusters rather than the sparse open clusters that currently form in the Milky Way. These "super star clusters" are likely precursors to globular clusters. Globular clusters in the Milky are all old, and there are indications that the early universe may have preferred to form these large clusters. The formation of super star clusters can be studied by observing the very youngest large star-forming regions, which are closest to their birth conditions. These regions are usually visually obscured by dust and gas clouds. The goal of this project is the detection of star formation in nearby galaxies in the infrared and radio wavelengths where star clusters and nebulae are not as affected by extinction as they are in the visible. Free-free radio continuum observations with the Very Large Array radio telescope will be used to map out radio nebulae surrounding young stars. Hidden nebulae can also be revealed by the mid-infrared emission from dust warmed by intense starlight from these clusters. With the Keck Telescope, nearby starbursts will be imaged in the mid-infrared at resolutions sufficient to distinguish gaseous nebulae from young star clusters. The first step is to locate the youngest super star clusters in nearby galaxies, where they are relatively easy to study. This is the major goal of this research. Eventually, once the locations of these clusters and their nebulae have been established, the imaging of gas clouds near the nebulae will show the relation of the clusters to their natal gas, which may reveal the trigger for the star formation. This is a topic that can be fruitfully explored with the future Atacama Large Millimeter Array telescope. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***