The process of star formation evolves spatially in a hierarchical way, leading, at parsec scales, to the formation of stellar clusters and associations. Star clusters, in particular, are gravitationally bound groups of up to millions of stars: they enclose a large fraction of the massive stars in galaxies that contribute to stellar feedback, and are therefore crucial for regulating the star formation lifecycle. In addition, star clusters can survive for hundreds of Myr, being good tracers of the star formation history inside their host galaxy. Despite their importance in the context of star formation, many fundamental questions concerning their formation and evolution remain open: how are their masses distributed, is it possible to form clusters of any mass? How long after their formation they get clear of their natal gas cloud? How long can they survive, are the young clusters observed in local galaxies going to evolve into globular clusters?
Similar questions arise when looking at star formation on larger scales: observations from the HST of high-redshift galaxies have revealed that star-forming clumps (on scales of ~100 pc) were denser and more frequent in the past, usually accounting for most of the UV light of their host galaxy. However, it is still to be understood in detail what are the main factors determining the ‘clumpiness’ of star-forming galaxies across cosmic times. The evolution of such large and massive clumps is equally important to understand, as it is strictly linked to the morphological evolution of the galaxies: for example, is it possible that such clumps are surviving long enough to drift toward the centre of galaxies and coalesce to form a bulge?
In this talk I will go through the main open questions concerning the formation and evolution of stellar clusters in nearby galaxies and of star-forming clumps across different redshifts and environments. I will focus on recent observational results, mainly related to HST observations/campaigns, showing how the properties of clustered star formation appear to be affected by local and global environment (e.g. star formation and gas surface densities) within galaxies.
Host: Hui Li