LEGACY EXTRAGALACTIC UV SURVEY (LEGUS) WITH THE<i>HUBBLE SPACE TELESCOPE</i>. I. SURVEY DESCRIPTION

Abstract

The Legacy ExtraGalactic UV Survey (LEGUS) is a Cycle 21 Treasury program on\nthe Hubble Space Telescope, aimed at the investigation of star formation and\nits relation with galactic environment in nearby galaxies, from the scales of\nindividual stars to those of ~kpc-size clustered structures. Five-band imaging,\nfrom the near-ultraviolet to the I-band, with the Wide Field Camera 3, plus\nparallel optical imaging with the Advanced Camera for Surveys, is being\ncollected for selected pointings of 50 galaxies within the local 12 Mpc. The\nfilters used for the observations with the Wide Field Camera 3 are: F275W(2,704\nA), F336W(3,355 A), F438W(4,325 A), F555W(5,308 A), and F814W(8,024 A); the\nparallel observations with the Advanced Camera for Surveys use the filters:\nF435W(4,328 A), F606W(5,921 A), and F814W(8,057 A). The multi-band images are\nyielding accurate recent (&lt;~50 Myr) star formation histories from resolved\nmassive stars and the extinction-corrected ages and masses of star clusters and\nassociations. The extensive inventories of massive stars and clustered systems\nwill be used to investigate the spatial and temporal evolution of star\nformation within galaxies. This will, in turn, inform theories of galaxy\nevolution and improve the understanding of the physical underpinning of the\ngas-star formation relation and the nature of star formation at high redshift.\nThis paper describes the survey, its goals and observational strategy, and the\ninitial science results. Because LEGUS will provide a reference survey and a\nfoundation for future observations with JWST and with ALMA, a large number of\ndata products are planned for delivery to the community.\n