New CO(1-0) Survey of Nearby Galaxies: Evolution of Molecular Gas and Star Formation in Galactic Disks

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A longstanding problem in astrophysics is to understand how galaxies form and develop throughout their lifetimes. Such understanding is necessary to uncover how our Universe evolved and to gain insight into the origin of our own Milky Way Galaxy. One important aspect of understanding galaxy formation and evolution is to develop detailed theories of star formation. As star formation occurs in giant molecular clouds (GMCs) within galaxies, astrophysicists study the formation and evolution of GMCs. With unprecedented high quality and high resolution data, this study will explore the evolution of GMCs and consequent star formation in galactic disks, and it will critically and quantitatively reconsider the standard picture of gas evolution in galaxies, specifically the one driven by stellar feedback. The study enables for the first time a census of GMC populations in substantial spiral galaxies.This project will also serve as a prototype for research with the Atacama Large Millimeter/submillimeter Array (ALMA) (a new international facility funded in part by the National Science Foundation), which will resolve the internal structure of GMCs in nearby galaxies and routinely produce images of molecular gas and star formation in very distant galaxies. For this project the investigators will use observations from their new CO survey of nearby galaxies with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Nobeyama Radio Observatory 45m telescope (NRO45), a survey that is nearly complete. The investigators will release to the astronomical community the CO data of nearby galaxies from CARMA and NRO45, and they will also release the software for the combination of interferometer and single-dish data developed for the survey.The investigating team also plans educational and outreach activities that involve building a radio interferometer for a hands-on astronomical laboratory course and disseminating the course materials to other schools. Because the concept of interferometry is challenging to master, developing such a hands-on laboratory course is crucial to the education of the next generation of radio astronomers for the ALMA era.