ALMA-IMF III -- Investigating the origin of stellar masses: Top-heavy
  core mass function in the W43-MM2&MM3 mini-starburst
  The ALMA-IMF Large Program observed the W43-MM2-MM3 ridge, whose 1.3mm and
3mm ALMA 12m array continuum images reach a 2500au spatial resolution. We used
both the best-sensitivity and the line-free ALMA-IMF images, reduced the noise
with the multi-resolution segmentation technique MnGSeg, and derived the most
complete and most robust core catalog possible. Using two different extraction
software packages, getsf and GExt2D, we identified 200 compact sources, whose
100 common sources have on average fluxes consistent to within 30%. We filtered
sources with non-negligible free-free contamination and corrected fluxes from
line contamination, resulting in a W43-MM2-MM3 catalog of 205 getsf cores. With
a median deconvolved FWHM size of 3400au, core masses range from 0.1Msun to
70Msun and the getsf catalog is 90% complete down to 0.8Msun. The high-mass end
of the core mass function (CMF) of W43-MM2-MM3 is top-heavy compared to the
canonical IMF. Fitting the cumulative CMF with a single power law of the form
N(>logM)\propto M^a, we measured a=-0.95\pm0.04, compared to the canonical
a=-1.35 Salpeter IMF slope. The slope of the CMF is robust with respect to map
processing, extraction software package, and reasonable variations in the
assumptions taken to estimate core masses. We explore several assumptions on
how cores transfer their mass to stars and sub-fragment to predict the IMF
resulting from the W43-MM2-MM3 CMF. In stark contrast to the commonly accepted
paradigm, our result argues against the universality of the CMF shape. More
robust functions of the star-formation efficiency and core sub-fragmentation
are required to better predict the resulting IMF, here suggested to remain
top-heavy at the end of the star-formation phase. If confirmed, the IMFs
emerging from starburst events could inherit their top-heavy shape from their
parental CMFs, challenging the IMF universality.
