Abstract:
Over the past years observations of young and populous star clusters have shown that the stellar initial mass function (IMF) appears to be an invariant featureless Salpeter power-law with an exponent alpha = 2.35 for stars more massive than a few Msol. A consensus has also emerged that most, if not all, stars form in stellar groups and star clusters, and that the mass function of young star clusters can be described as a power-law (the embedded cluster mass function, ECMF) with an exponent beta ~ 2. These two results imply that the integrated galactic-field IMF (IGIMF) for early-type stars cannot be a Salpeter power-law, but that they must have a steeper exponent. This has important consequences for the distribution of stellar remnants and for the chemo-dynamical and photometric evolution of galaxies.