EPoS Contribution
EPoS Contribution
ALMA-IMF, a Large Program investigating the origin of stellar masses

Yohan Pouteau
IPAG, Grenoble, FR
The origin of stellar masses, arguably the most central question in star formation remains a major open issue in modern astrophysics. The main goal of the ALMA-IMF Large Program (PIs Motte, Ginsburg, Louvet, & Sanhueza) is to determine how the origin of the initial mass function (IMF) is in fact dependent on cloud characteristics or not. Our pilot study and preliminary ALMA-IMF results show that the mass distribution of cores (CMFs) in these typical yet extreme environments of the Milky Way present an excess of high-mass cores with respect to the canonical IMF. I will present a detailed study of two contiguous protoclusters, W43-MM2 and W43-MM3, which are at different evolutionary stages and suggest that the CMF deviates from the canonical IMF form when and where a burst of star formation develops. The CMF would thus strongly depend on environmental parameters and may lead to non-universal stellar IMFs and heterogenous, mass-segregated spatial distribution of stars. In addition, we compare the CMF of prestellar and protostellar cores and prove that the relationship between the CMF and IMF should be revised because, in the case of intermediate-to-high-mass star, the prestellar phase is evanescent if it exists at all. The ALMA-IMF Large Program therefore has the potential to transform our understanding of the IMF origin. It also provides the community with an unprecedented database.
Caption: (a): The W43-MM2 and MM3 protocluster cloud, as imaged by ALMA at 1.3mm. White ellipses outline the FWHM size of compact cores extracted by getsf. This image is slit into six subregions, defined by a multi- resolution analysis separating 0.5–1 pc cloud structures. The three sub- regions with top-heavy CMFs (see panel b) are outlined by violet contours while the three remaining subregions display Salpeter-like CMFs (b): Top-heavy CMF (red histogram) measured for the three densest and most massive subregions, outlined by violet contours in panel (a), compared to the Salpeter-like CMF (green histogram, α = −1.35) measured for the remaining subregions of the W43-MM2 and MM3 protocluster cloud. (c) : N-PDFs of the W43-MM2 and MM3 protocluster cloud (blue points) and subregions with a top-heavy CMFs (in red) and CMFs with high-mass ends close to Salpeter (in green). PDF tails are fitted by powerlaws, whose slopes remind those measured for clouds dominated by gravity and, for the flatter tail, those found for cloud ridges/hubs forming high- mass stars.
Collaborators:
F. Motte, IPAG, FR
T. Nony, IRA-UNAMM, MX
F. Louvet, IPAG, FR
and ALMA-IMF consortium
Key publication

Suggested Session: Cores