Understanding the star formation mechanisms from a Galaxy-wide point of view

The formation mechanism of the stars, in particular of the most massive ones, is still an open question for our community. Several competing theories have been proposed in the past few years, all aimed to understand and predict the multi-scale star formation process: how from the parent molecular clouds, at the scales of several tens of pc, we form the long filaments and, within them, the parsec-scales clumps inside which, down to the thousands of AU scales, the final cluster of stars forms. The major difficulties are due to the fact that in these complex star-forming regions it is extremely hard to disentangle the various contributions from gravity, turbulence, magnetic fields, feedback and impact of the local environment, which all act combined in a yet unpredictable ways. In this talk I will present the main results obtained by the IAPS star formation group to investigate the (massive) star formation mechanism, from the historical approach of building up a statistically significant sample of regions to analyze the problem from a Galaxy-wide point of view, to the most recent efforts aimed to compare our results with the most advanced numerical simulations. In the recent past we have carried out the largest survey proposed with the Herschel telescope, Hi-GAL, which has allowed us to identify tens of thousands of Galactic filaments and hundreds of thousands of star-forming clumps, opening up new windows to study the formation of massive objects on a statistical basis. Thanks to the role of leadership in the field, a selection of ~1000 clumps in Hi-GAL have been used to carry out the largest survey of clumps observed with ALMA down to ~1500 AU resolution, the ALMAGAL project. The first results from this unique survey is showing a large variety of properties of the innermost cores which will form the final cluster of stars, which only a comparison with a dedicated set of simulations may help to interpret. We are now carrying out the so-called "Rosetta Stone project”, thanks to the fundings of the ERC synergy grant ECOGAL. This project aims to produce suites of dedicated simulations of star forming regions at various scales and post-process them towards a dedicated pipeline which will finally produce synthetic observations as close as possible to real observations, opening up an innovative and comprehensive comparison between simulations and observations. I will finally conclude my talk with the future perspectives of our team, focused in investigating the star-formation mechanisms with Galaxy-wide surveys proposed for the incoming facilities such as SKA and AtLAST.