Collaborative Research: Dust, Gas, and Star Formation: Synthesizing 20 Years of Radio, Millimeter, and Infrared Surveys

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Galaxies grow by converting interstellar gas into new generations of stars. A main step in that process is the conversion of low-density, atomic gas into cold, dense, star-forming clouds. Interstellar dust controls this process by shielding gas from destructive ultraviolet radiation and promoting chemical reactions. The abundance of both dust and cold gas depend on local environment in a galaxy, but the nature of this dependence is still debated at a very basic level. This project will test competing hypotheses for what sets the amount of dust and cold gas in galaxies by mapping dust, neutral interstellar gas (diffuse atomic gas and cold, dense molecular gas), and local conditions in a sample of nearby galaxies ten times larger than those used in previous studies. The investigators will use these observations database to answer two questions about gas and star formation in galaxies. The first question is what sets the amount of cold, star-forming gas? The second question is what determines the abundance of dust? These two intertwined questions are critical to understand how galaxies grow and change over time.The investigators will assemble the next generation database of dust and gas distributions in galaxies. To do this, they will combine new and archival observations of atomic hydrogen (HI) from the NSF-funded Very Large Array with Herschel spacecraft measurements of the distribution and properties of interstellar dust. They will increase, by an order of magnitude, the sample of galaxies with such observations. An order of magnitude increase in the set of galaxies studied in this way will advance the field into a new regime of statistical hypothesis testing, a potentially transformative step in understanding the physics of gas in galaxies.The observing database will be shared on the internet with other astronomers and also the public. The investigators will build on the Zooniverse project to share their observations with the public. Zooniverse is an internet tool that allows the public to view and classify scientific observations. With this tool, the public can both appreciate the observations and aid in the research. The investigators plan to create 'the HI Holes Project', in which volunteer citizen scientists will identify giant holes in the gaseous interstellar medium of real and simulated galaxies.