High-Mass Star and Massive Cluster Formation in the Milky Way

This review examines the state-of-the-art knowledge of high-mass star and massive cluster formation, gained from ambitious observational surveys, which acknowledges the multiscale characteristics of these processes. After a brief overview of theoretical models and main open issues, we present observational searches for the evolutionary phases of high-mass star formation, first among high-luminosity sources and more recently among young massive protostars and the elusive high-mass prestellar cores. We then introduce the most likely evolutionary scenario for high-mass star formation, which emphasizes the link of high-mass star formation to massive cloud and cluster formation. Finally, we introduce the first attempts to search for variations of the star-formation activity and cluster formation in molecular cloud complexes in the most extreme star-forming sites and across the Milky Way. The combination of Galactic plane surveys and high–angular resolution images with submillimeter facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to make significant progress in the forthcoming decade.