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The unexpectedly large proportion of high-mass star-forming cores in a Galactic mini-starburst


Understanding the processes that determine the stellar initial mass function (IMF) is a critical unsolved problem, with profound implications for many areas of astrophysics1. In molecular clouds, stars are formed in cores—gas condensations sufficiently dense that gravitational collapse converts a large fraction of their mass into a star or small clutch of stars. In nearby star-formation regions, the core mass function (CMF) is strikingly similar to the IMF, suggesting that the shape of the IMF may simply be inherited from the CMF2,3,4,5. Here, we present 1.3 mm observations, obtained with the Atacama Large Millimeter/submillimeter Array telescope, of the active star-formation region W43-MM1, which may be more representative of the Galactic-arm regions where most stars form6,7. The unprecedented resolution of these observations reveals a statistically robust CMF at high masses, with a slope that is markedly shallower than the IMF. This seriously challenges our understanding of the origin of the IMF.

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Fig. 1: High-angular-resolution image of the W43-MM1 cloud, revealing a rich population of cores.
Fig. 2: W43-MM1 CMFs challenging the relationship between the CMF and IMF.
Fig. 3: Mean estimated dust temperatures for cores.


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This paper makes use of the following ALMA data: #2013.1.01365.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This project has received funding from the European Union’s Horizon 2020 research and innovation programme StarFormMapper under grant agreement number 687528. This work was supported by the Programme National de Physique Stellaire and Physique et Chimie du Milieu Interstellaire of CNRS/INSU (with INC/INP/IN2P3), co-funded by CEA and CNES. A.P.W. gratefully acknowledges the support of a consolidated grant (ST/K00926/1) from the UK Science and Technology Funding Council. T.C. acknowledges support from the Deutsche Forschungsgemeinschaft via the SPP (priority programme) 1573 ‘Physics of the ISM’. A.J.M. has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (MagneticYSOs, grant agreement number 679937).

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Authors and Affiliations



F.M. and F.L. led the project. E.C., T.N., F.M. and A.J.M. reduced the ALMA data. F.L. ran getsources and the CASA simulator. T.C. ran MRE-GaussClumps. K.A.M. ran PPMAP. S.B. and A.M. performed the Monte Carlo simulations. F.M., T.N. and F.L. analysed the CMF results. F.M. and A.P.W. wrote the manuscript. F.M., S.B., F.L., Q.N.L., A.J.M. and P.S. contributed to the ALMA proposal. All authors discussed the results and implications and commented on the manuscript.

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Correspondence to F. Motte, T. Nony or F. Louvet.

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Supplementary Figures 1–2, Supplementary Tables 1–2

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Motte, F., Nony, T., Louvet, F. et al. The unexpectedly large proportion of high-mass star-forming cores in a Galactic mini-starburst. Nat Astron 2, 478–482 (2018).

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