Extreme Galaxies: The Physical Nature of SMUDGes

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Galaxies consist of normal matter embedded in a larger halo of dark matter. Understanding how normal matter distributes itself within the dark matter halo is important to understanding how galaxies grow and evolve. This project will study ultra-diffuse galaxies (UDGs), a class of galaxies that are comparable in size to the Milky Way, but seem to have very few stars. The project will combine data from a previous survey (SMUDGes) with existing data from other sources and new data to catalog physical characteristics of UDGs. These characteristics include sizes, ages, masses, and metallicities. By building a large enough catalog, this project will be able to better understand UDGs and where they fit into the general class of galaxies. The project will also support the Sky Ambassadors program that trains teachers to present astronomy in their classrooms. It will initiate a Spanish language public lecture series at the Steward Observatory.The project will use galaxies found in the SMUDGes survey to build a statistically meaningful catalog of UDG physical properties. The project will use clustering data from SMUDGes to determine distance measurements to UDGs in dense environments, they will also use spectrographic observations taken on the Large Binocular Telescope to obtain redshift distances for interesting targets such as those that appear to be very large or are in quiescent fields. They will use archival UV data to determine color of UDGs and the more physically interesting ones may be flagged for follow-up spectroscopy. The resulting catalog will provide a large sample of UDG characteristics that can be used to better understand if these objects are a separate class or if they are an extended tail of a broad distribution of galaxies. The project will also continue a program that trains elementary through high-school teachers to use astronomy in their classrooms. They will also initiate and sponsor Spanish language lectures as part of the Steward Observatory Public Lecture Series.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.