Clustered Star Formation on various scales. An extensive panchromatic stellar survey of star-forming galaxies in the Local Group with the Hubble Space Telescope

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Stars are formed in groups of various scales and with various degrees of gravitational self-binding. A large variety of stellar concentrations, from small compact clusters to large loose complexes, host the majority of young stars in a galaxy, and feed its field with stars, playing a fundamental role in galaxy evolution. This DFG project will utilize three unique deep extragalactic stellar surveys with the Hubble Space Telescope (HST) to address fundamental questions on the formation and the evolution of structures of stars on various scales and environments.The first funding period of the project supported my contribution to the Panchromatic Hubble Space Telescope Andromeda Galaxy Treasury program (PI: J. J. Dalcanton), on the most complete stellar coverage ever achieved in the Andromeda galaxy. Although the survey is not yet complete, first data on portions of the survey delivered remarkable results on clustered star formation at galactic scales. The applied extension will allow the participation of this project to the global astrophysical inference of the Andromeda galaxy through the full exploitation of the complete survey. It will also allow us to further investigate clustered star formation in a variety of environments, and across a wide range of time and spatial scales, through the employment of data from two additional HST Treasury programs: (i) The impressive star-forming region of the Tarantula Nebula, will be investigated with data from the Hubble Tarantula Nebula Treasury Program (PI: E. Sabbi), and (ii) the Legacy ExtraGalactic UV Survey (PI: D. Calzetti) will construct the most complete stellar survey in five wavebands of 50 star-forming spiral and dwarf galaxies in the Local Group. These programs will advance the scientific impact of this DFG project, by extending the Andromeda findings to an exceptional collection of star-forming environments.This ambitious project will comprehend important issues of the formation of stars in groups in collaboration with more than 40 colleagues worldwide. Direct objectives of the project is to understand: (1) How clustered star formation proceeds in time and space; (2) Which mechanisms determine stellar structure at the time of formation; (3) What is the origin of the observed variety in size, shape and compactness in stellar clusterings; (4) How the environment affects clustered star formation and its subsequent dynamical evolution. Data from all three deep panchromatic HST surveys of extragalactic stellar populations will significantly advance the investigation of these topics in a wide range of spatial resolutions, starting from parsec-scale in the Large Magellanic Cloud, to 10 parsec-scale in the Andromeda galaxy, to 100 parsec-scale, in more distant galaxies. The various stellar populations, resolved in a large collection of galaxies, will provide unprecedented samples to address stellar structure formation and evolution in a thorough and consistent way.