LEGUS: Legacy ExtraGalactic UV Survey

LEGUS: Legacy ExtraGalactic UV Survey LEGUS: Legacy ExtraGalactic UV Survey II. Program Summary The LEGUS Program is awarded 154 orbits in Cycle 21 to build therst HST UV Atlas of 51 nearby star-forming galaxies, carefully selected to span the full range of morphology, star formation rate (SFR), mass, metallicity, internal structure, and interaction state found in the local Universe. In combination with archival and new optical UBVI WFC3/ACS data, the requested WFC3 UV images are key for deriving accurate recent (<50 Myr) star formation histories (SFHs) from resolved massive stars, and the extinction-free ages and masses of star clusters and associations. These extensive inventories of massive stars, clustered systems, and SFHs will be used to: (1) quantify how the clustering of star formation evolves both in space and in time; (2) discriminate among models of star cluster evolution; (3) investigate the eects of SFH on the UV SFR calibrations; (4) explore the impact of environment on star formation and cluster evolution across the full range of galactic and ISM properties. The proper analysis of these data will require signicant eort, primarily because of the need to perform careful crowded-eld photometry on resolved, partially resolved and unresolved stars and star clusters in these images, in order to construct color-magnitude diagrams (CMDs) and color-color diagrams. It will also require us to test the photometry software packages and determine the best automated approach to use for cluster identication and photometry before the LEGUS data arrives. We will also build manual catalogs for the LEGUS target galaxies to compare with the automatically produced cluster catalogs. Under these considerations we believe that the project will require approximately seven months of labor from the ASU P.I. Dr. Hwihyun Kim, working on a full-time basis as a postdoc. She will be collaborating with the project P.I. Dr. Calzetti at UMass and co-I. Dr. Whitmore at STScI. Prof. Windhorst (ASU Admin. P.I.) will not require any funding from this project.