Investigating the origin of stellar masses: an overview of the ALMA Large Program

The origin of stellar masses is one of the most central open issues in astrophysics. In this talk, I will introduce the ALMA-IMF Large Program, whose goal is to determine if and how the origin of the Initial Mass Function (IMF) depends on the cloud characteristics. I will also present our recent detailed studies of the W43-MM2&MM3 molecular complex. We propose that top-heavy Core Mass Functions are associated with spatially and temporally limited bursts of star formation. In addition, the identification of outflows in CO(2-1) enables us to assess that a very large fraction of the excess high-mass cores are protostellar. This confirms that the high-mass prestellar core phase, if it exists, is evanescent.