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.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


  1. 1.

    Offner, S. S. R. et al. in Protostars and Planets VI (eds Beuther, H., Klessen, R. S., Dullemond, C, P. & Henning, Th.) 53–75 (Univ. Arizona Press, Tucson, 2014).

  2. 2.

    Motte, F., André, P. & Neri, R. The initial conditions of star formation in the Rho Ophiuchi main cloud: wide-field millimeter continuum mapping. Astron. Astrophys. 336, 150–172 (1998).

  3. 3.

    Testi, L. & Sargent, A. I. Star formation in clusters: a survey of compact millimeter-wave sources in the Serpens Core. Astrophys. J. Lett. 508, L91–L94 (1998).

  4. 4.

    Enoch, M. L. et al. The mass distribution and lifetime of prestellar cores in Perseus, Serpens, and Ophiuchus. Astrophys. J. 684, 1240–1259 (2008).

  5. 5.

    Könyves, V. et al. A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey. Astron. Astrophys. 584, A91 (2015).

  6. 6.

    Nguyen Luong, Q. et al. Low-velocity shocks traced by extended SiO emission along the W43 ridges: witnessing the formation of young massive clusters. Astrophys. J. 775, 88 (2013).

  7. 7.

    Louvet, F. et al. The W43-MM1 mini-starburst ridge, a test for star formation efficiency models. Astron. Astrophys. 570, A15 (2014).

  8. 8.

    Bastian, N., Covey, K. R. & Meyer, M. R. A universal stellar initial mass function? A critical look at variations. Annu. Rev. Astron. Astrophys. 48, 339–389 (2010).

  9. 9.

    Kroupa, P. et al. in Planets, Stars and Stellar Systems Vol. 5 (eds Oswalt, T. D. & Gilmore, G.) 115 (Springer, Dordrecht, 2013).

  10. 10.

    Harayama, Y., Eisenhauer, F. & Martins, F. The initial mass function of the massive star-forming region NGC 3603 from near-infrared adaptive optics observations. Astrophys. J. 675, 1319–1342 (2008).

  11. 11.

    Maia, F. F. S., Moraux, E. & Joncour, I. Young and embedded clusters in Cygnus-X: evidence for building up the initial mass function? Mon. Not. R. Astron. Soc. 458, 3027–3046 (2016).

  12. 12.

    Motte, F., Bontemps, S. & Louvet, F. High-mass star and massive cluster formation in the Milky Way. Annu. Rev. Astron. Astrophys. https://doi.org/10.1146/annurev-astro-091916-055235 (2018).

  13. 13.

    André, P. et al. From filamentary clouds to prestellar cores to the stellar IMF: initial highlights from the Herschel Gould Belt survey. Astron. Astrophys. 518, L102 (2010).

  14. 14.

    Bontemps, S., Motte, F., Csengeri, T. & Schneider, N. Fragmentation and mass segregation in the massive dense cores of Cygnus X. Astron. Astrophys. 524, A18 (2010).

  15. 15.

    Zhang, Q., Wang, K., Lu, X. & Jiménez-Serra, I. Fragmentation of molecular clumps and formation of a protocluster. Astrophys. J. 804, 141 (2015).

  16. 16.

    Cheng, Y. et al. The core mass function in the massive protocluster G286.21+0.17 revealed by ALMA. Astrophys. J. 853, 160 (2018).

  17. 17.

    Motte, F., Schilke, P. & Lis, D. C. From massive protostars to a giant H ii region: submillimeter imaging of the Galactic ministarburst W43. Astrophys. J. 582, 277–291 (2003).

  18. 18.

    Nguyen Luong, Q. et al. W43: the closest molecular complex of the Galactic bar? Astron. Astrophys. 529, A41 (2011).

  19. 19.

    Louvet, F. et al. Tracing extended low-velocity shocks through SiO emission. Case study of the W43-MM1 ridge. Astron. Astrophys. 595, A122 (2016).

  20. 20.

    Men’shchikov, A. et al. A multi-scale, multi-wavelength source extraction method: getsources. Astron. Astrophys. 542, A81 (2012).

  21. 21.

    Maíz Apellániz, J. & Úbeda, L. Numerical biases on initial mass function determinations created by binning. Astrophys. J. 629, 873–880 (2005).

  22. 22.

    Salpeter, E. E. The luminosity function and stellar evolution. Astrophys. J. 121, 161 (1955).

  23. 23.

    Marsh, K. A., Whitworth, A. P. & Lomax, O. Temperature as a third dimension in column-density mapping of dusty astrophysical structures associated with star formation. Mon. Not. R. Astron. Soc. 454, 4282–4292 (2015).

  24. 24.

    Herpin, F. et al. The massive protostar W43-MM1 as seen by Herschel-HIFI water spectra: high turbulence and accretion luminosity. Astron. Astrophys. 542, A76 (2012).

  25. 25.

    Sridharan, T. K. et al. Hot core, outflows, and magnetic fields in W43-MM1 (G30.79 FIR 10). Astrophys. J. Lett. 783, L31 (2014).

  26. 26.

    Motte, F. & André, P. The circumstellar environment of low-mass protostars: a millimeter continuum mapping survey. Astron. Astrophys. 365, 440–464 (2001).

  27. 27.

    Hatchell, J. & Fuller, G. A. Star formation in Perseus. IV. Mass-dependent evolution of dense cores. Astron. Astrophys. 482, 855–863 (2008).

  28. 28.

    Swift, J. J. & Williams, J. P. On the evolution of the dense core mass function. Astrophys. J. 679, 552–556 (2008).

  29. 29.

    Csengeri, T. et al. The ATLASGAL survey: a catalog of dust condensations in the Galactic plane. Astron. Astrophys. 565, A75 (2014).

  30. 30.

    Clark, P. C., Klessen, R. S. & Bonnell, I. A. Clump lifetimes and the initial mass function. Mon. Not. R. Astron. Soc. 379, 57–62 (2007).

  31. 31.

    McMullin, J. P., Waters, B., Schiebel, D., Young, W. & Golap, K. CASA architecture and applications. In Astronomical Data Analysis Software and Systems XVI (eds Shaw, R. A., Hill, F. & Bell, D. J.) 376, 127 (Astronomical Society of the Pacific, 2007).

  32. 32.

    Rau, U. & Cornwell, T. J. A multi-scale multi-frequency deconvolution algorithm for synthesis imaging in radio interferometry. Astron. Astrophys. 532, A71 (2011).

  33. 33.

    Hennemann, M. et al. The spine of the swan: a Herschel study of the DR21 ridge and filaments in Cygnus X. Astron. Astrophys. 543, L3 (2012).

  34. 34.

    Men’shchikov, A. A multi-scale filament extraction method: getfilaments. Astron. Astrophys. 560, A63 (2013).

  35. 35.

    Ossenkopf, V. & Henning, T. Dust opacities for protostellar cores. Astron. Astrophys. 291, 943–959 (1994).

  36. 36.

    Tigé, J. et al. The earliest phases of high-mass star formation, as seen in NGC 6334 by Herschel-HOBYS. Astron. Astrophys. 602, A77 (2017).

  37. 37.

    Bracco, A. et al. Probing changes of dust properties along a chain of solar-type prestellar and protostellar cores in Taurus with NIKA. Astron. Astrophys. 604, A52 (2017).

  38. 38.

    Reid, M. A. & Wilson, C. D. High-mass star formation. III. The functional form of the submillimeter clump mass function. Astrophys. J. 650, 970–984 (2006).

Download references


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).

Author information


  1. Institut de Planétologie et d’Astrophysique de Grenoble, Université Grenoble Alpes, CNRS, Grenoble, France

    • F. Motte
    •  & T. Nony
  2. AIM Paris-Saclay/Département d’Astrophysique, CEA, CNRS, Université Paris Diderot, CEA-Saclay, Gif-sur-Yvette, France

    • F. Motte
    • , A. Men’shchikov
    • , A. J. Maury
    • , V. Könyves
    • , P. Didelon
    •  & M. Gaudel
  3. Department of Astronomy, Universidad de Chile, Santiago, Chile

    • F. Louvet
  4. School of Physics and Astronomy, Cardiff University, Cardiff, UK

    • K. A. Marsh
    • , A. P. Whitworth
    •  & A. Duarte-Cabral
  5. Laboratoire d’Astrophysique de Bordeaux, OASU, Université Bordeaux, CNRS, Pessac, France

    • S. Bontemps
    •  & E. Chapillon
  6. Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea

    • Q. Nguyễn Lương
  7. NAOJ Chile Observatory, National Astronomical Observatory of Japan, Tokyo, Japan

    • Q. Nguyễn Lương
  8. Max-Planck-Institut für Radioastronomie, Bonn, Germany

    • T. Csengeri
  9. LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Université, Paris, France

    • A. Gusdorf
  10. Institut de Radioastronomie Millimétrique, Saint Martin d’Hères, France

    • E. Chapillon
  11. Physikalisches Institut, University of Cologne, Cologne, Germany

    • P. Schilke


  1. Search for F. Motte in:

  2. Search for T. Nony in:

  3. Search for F. Louvet in:

  4. Search for K. A. Marsh in:

  5. Search for S. Bontemps in:

  6. Search for A. P. Whitworth in:

  7. Search for A. Men’shchikov in:

  8. Search for Q. Nguyễn Lương in:

  9. Search for T. Csengeri in:

  10. Search for A. J. Maury in:

  11. Search for A. Gusdorf in:

  12. Search for E. Chapillon in:

  13. Search for V. Könyves in:

  14. Search for P. Schilke in:

  15. Search for A. Duarte-Cabral in:

  16. Search for P. Didelon in:

  17. Search for M. Gaudel in:


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.

Competing interests

The authors declare no competing interests.

Corresponding authors

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

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–2, Supplementary Tables 1–2

About this article

Publication history




Issue Date