The JWST LEGGOS Survey: Taking Galaxies Apart and Putting Them Back, a Clump at a Time

I will present an overview of the JWST LEGGOS program (LEnsed Galaxies: Growth of Substructures) – an 85-hour Cycle 2 JWST survey to spatially and spectrally resolve the building blocks of star-forming galaxies at cosmic noon and beyond. LEGGOS uses the full range of spectral resolution available on the NIRSpec IFU mode for a sample of strong gravitationally-lensed galaxies to measure both stellar continuum (at R~100) and nebular line emission (at R~1000-2700) from resolved clumpy structures reaching down to 10's of parsecs in size. The JWST data allow us to precisely constrain the basic properties of these small clumps, including stellar population ages, sizes, dust content, metallicities, nebular ionization properties, and bulk dynamics. LEGGOS, for the first time, unpacks the diversity of stellar populations and star formation histories of individual clumps within distant star-forming galaxies, and allows us to directly reconstruct how those galaxies are assembled from their constituent structures. In this talk, I will present first measurements from LEGGOS that exhibit the diversity in star formation histories in 10-50 parsec regions beyond cosmic noon. The growing number of highly magnified systems with these measurements provides a path toward understanding mass assembly via the earliest star-bursting clusters in galaxies across cosmic time.