ALMA-IMF VI -- Investigating the origin of stellar masses: Core mass function evolution in the W43-MM2&MM3 mini-starburst

TL;DR

This study investigates how the core mass function (CMF) evolves in the W43-MM2&MM3 mini-starburst region, revealing that the CMF can shift from a Salpeter slope to a top-heavy distribution during different star formation stages.

Contribution

It provides the first detailed analysis of CMF evolution within a mini-starburst, linking cloud properties and star formation stages to changes in the CMF shape.

Findings

CMF varies from Salpeter to top-heavy across different regions.

Flat second n-PDF tails correlate with top-heavy CMFs.

CMF evolution may follow the star formation process stages.

Abstract

Among the most central open questions regarding the initial mass function (IMF) of stars is the impact of environment on the shape of the core mass function (CMF) and thus potentially on the IMF. The ALMA-IMF Large Program aims to investigate the variations in the core distributions with cloud characteristics, as diagnostic observables of the formation process and evolution of clouds. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has recently been found to be top-heavy with respect to the Salpeter slope. W43-MM2&MM3 harbors a rich cluster that contains a statistically significant number of cores, which was previously characterized in Paper III. We applied a multi-scale decomposition technique to the ALMA 1.3 mm and 3 mm continuum images to define six subregions. For each subregion we characterized the high column density probability distribution function, n-PDF, and the shape of the cloud gas using the 1.3 mm image. Using the core catalog, we investigate correlations between the CMF and cloud and core properties. We classify the subregions into different stages of evolution, from quiescent to burst to post-burst, based on the surface number density of cores, number of outflows, and UCHii presence. The high-mass end of the subregion CMFs varies from being close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst). Moreover, the second tail of the n-PDF varies from steep, to flat like observed for the high mass star-forming clouds. We found that subregions with flat second n-PDF tails display top-heavy CMFs. The CMF may evolve from Salpeter to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises the question of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, a hypothesis that remains to be tested.