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Abstract

Giant molecular clouds (GMCs) form stars with initial conditions set by their local host galaxy environment, which feedback energy and matter into their surroundings, contributing to galaxy evolution. However, the detailed characteristics of these processes between molecular gas and young stars remain elusive, primarily due to a lack of observational constraints. By capitalizing on CO and Halpha observations from PHANGS, we have systematically measured the evolutionary timeline from GMCs to exposed HII regions, across 54 galaxies, the largest and most statistically complete sample to-date. Strong correlations between GMC evolutionary time-scales and the host galaxy properties have been identified, revealing the connection between galactic-scale dynamics and the small-scale GMC lifecycle. Furthermore, in the 5 nearest galaxies of my sample (D<3.5Mpc), we have established that the initial half of the embedded star formation detected in Spitzer 24microns is invisible in Halpha. Finally, using novel JWST observations of NGC628 with 10 times better resolution compared to Spitzer, we have further demonstrated that the embedded phase of star formation can be characterized at a greater distance (D=9.8Mpc), pioneering the way for the systematic determination of the early phases of star formation across the nearby galaxy population (up to 20Mpc) with PHANGS-JWST.