How Do Galaxies End Their Star-Formation?

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This project will investigate the population of galaxies that are in transition from star-forming to non-star-forming, with greater accuracy than was previously possible. The Principal Investigator and graduate students supported by the award will combine optical-wavelength data from the Sloan Digital Sky Survey, ultraviolet data from the Galaxy Evolution Explorer (GALEX) spacecraft, and mid-infrared data from the Wide-Field Infrared Survey Explorer (WISE) spacecraft, to identify transition galaxies and to constrain their metallicities, star-formation rates, dust extinctions, stellar masses, and active nucleus content at low redshift. They will then use PRIMUS, a 120,000 galaxy survey sampling the redshift range between 0.2 and 1.0, combined with GALEX and Spitzer Space Telescope data, to perform a similar analysis at higher redshift. The objectives are (1) to obtain an accurate and representative census of the transition population; (2) to determine whether star-formation is turning off the same way in isolated galaxies as in cluster populations; and (3) to determine whether active galactic nuclei are related to the transition phenomenon. In addition to supporting graduate student training, the project will enable expansion of the NASA-Sloan Atlas of galaxies to include newly released WISE data and development of educational and outreach tools within the existing web interface.