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Systematic variation of the stellar initial mass function in early-type galaxies

Nature volume 484, pages 485–488 (2012)Cite this article

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Abstract

Much of our knowledge of galaxies comes from analysing the radiation emitted by their stars, which depends on the present number of each type of star in the galaxy. The present number depends on the stellar initial mass function (IMF), which describes the distribution of stellar masses when the population formed, and knowledge of it is critical to almost every aspect of galaxy evolution. More than 50 years after the first IMF determination1, no consensus has emerged on whether it is universal among different types of galaxies2. Previous studies indicated that the IMF and the dark matter fraction in galaxy centres cannot both be universal3,4,5,6,7, but they could not convincingly discriminate between the two possibilities. Only recently were indications found that massive elliptical galaxies may not have the same IMF as the Milky Way8. Here we report a study of the two-dimensional stellar kinematics for the large representative ATLAS3D sample9 of nearby early-type galaxies spanning two orders of magnitude in stellar mass, using detailed dynamical models. We find a strong systematic variation in IMF in early-type galaxies as a function of their stellar mass-to-light ratios, producing differences of a factor of up to three in galactic stellar mass. This implies that a galaxy’s IMF depends intimately on the galaxy's formation history.

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Figure 1: Differentiating between the stellar and dark matter with integral-field stellar kinematics.
Figure 2: Systematic variation of the IMF in early-type galaxies.

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Acknowledgements

M.C. acknowledges support from a Royal Society University Research Fellowship. This work was supported by the rolling grants ‘Astrophysics at Oxford’ from the UK Research Councils. R.L.D. acknowledges support from Christ Church College, Oxford University, and from the Royal Society in the form of a Wolfson Merit Award. S.K. acknowledges support from the Royal Society Joint Projects Grant. R.M.M. is supported by the Gemini Observatory. T.N. and M. Bois acknowledge support from the DFG Cluster of Excellence ‘Origin and Structure of the Universe’. M.S. acknowledges support from a STFC Advanced Fellowship. N.S. and T.A.D. acknowledge support from an STFC studentship.

Author information

Authors and Affiliations

  1. Sub-department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK,

    Michele Cappellari, M. Bureau, Roger L. Davies, Timothy A. Davis & Nicholas Scott

  2. Gemini Observatory, Northern Operations Centre, 670 North A’ohoku Place, Hilo, Hawaii 96720, USA ,

    Richard M. McDermid

  3. Department of Astronomy, Campbell Hall, University of California, Berkeley, 94720, California, USA

    Katherine Alatalo & Leo Blitz

  4. Observatoire de Paris, LERMA and CNRS, 61 Avenue de l’Observatoire, F-75014 Paris, France ,

    Maxime Bois

  5. Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp CNRS Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France ,

    Frédéric Bournaud & Pierre-Alain Duc

  6. Department of Astrophysics, University of Massachusetts, 710 North Pleasant Street, Amherst, Massachusetts 01003, USA,

    Alison F. Crocker

  7. European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany ,

    Timothy A. Davis, P. T. de Zeeuw, Eric Emsellem, Davor Krajnović, Harald Kuntschner & Pierre-Yves Lablanche

  8. Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands ,

    P. T. de Zeeuw

  9. Université Lyon 1, Observatoire de Lyon, Centre de Recherche Astrophysique de Lyon and Ecole Normale Supérieure de Lyon, 9 avenue Charles André, F-69230 Saint-Genis Laval, France ,

    Eric Emsellem & Pierre-Yves Lablanche

  10. Max-Planck Institut für extraterrestrische Physik, PO Box 1312, D-85478 Garching, Germany ,

    Sadegh Khochfar

  11. Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands ,

    Raffaella Morganti, Tom Oosterloo & Paolo Serra

  12. Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands ,

    Raffaella Morganti & Tom Oosterloo

  13. Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany ,

    Thorsten Naab

  14. Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL1 9AB, UK ,

    Marc Sarzi

  15. Centre for Astrophysics & Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122, Australia ,

    Nicholas Scott

  16. Dunlap Institute for Astronomy & Astrophysics, University of Toronto, 50 St George Street, Toronto, Ontario M5S 3H4, Canada ,

    Anne-Marie Weijmans

  17. Physics Department, New Mexico Institute of Mining and Technology, Socorro, 87801, New Mexico, USA

    Lisa M. Young

Authors
  1. Michele Cappellari
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  2. Richard M. McDermid
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  3. Katherine Alatalo
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  4. Leo Blitz
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  5. Maxime Bois
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  7. M. Bureau
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  18. Raffaella Morganti
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  19. Thorsten Naab
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  21. Marc Sarzi
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  22. Nicholas Scott
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Contributions

All authors contributed extensively to the work presented in this paper.

Corresponding author

Correspondence to Michele Cappellari.

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The authors declare no competing financial interests.

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Cappellari, M., McDermid, R., Alatalo, K. et al. Systematic variation of the stellar initial mass function in early-type galaxies. Nature 484, 485–488 (2012). https://doi.org/10.1038/nature10972

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