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Early assembly of the most massive galaxies


The current consensus is that galaxies begin as small density fluctuations in the early Universe and grow by in situ star formation and hierarchical merging1. Stars begin to form relatively quickly in sub-galactic-sized building blocks called haloes which are subsequently assembled into galaxies. However, exactly when this assembly takes place is a matter of some debate2,3. Here we report that the stellar masses of brightest cluster galaxies, which are the most luminous objects emitting stellar light, some 9 billion years ago are not significantly different from their stellar masses today. Brightest cluster galaxies are almost fully assembled 4-5 billion years after the Big Bang, having grown to more than 90 per cent of their final stellar mass by this time. Our data conflict with the most recent galaxy formation models4,5 based on the largest simulations of dark-matter halo development1. These models predict protracted formation of brightest cluster galaxies over a Hubble time, with only 22 per cent of the stellar mass assembled at the epoch probed by our sample. Our findings suggest a new picture in which brightest cluster galaxies experience an early period of rapid growth rather than prolonged hierarchical assembly.

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Figure 1: Infrared image of the cluster J2235.
Figure 2: The stellar evolution of BCGs with redshift.
Figure 3: The mass evolution of BCGs with redshift.


  1. Springel, V. et al. Simulations of the formation, evolution and clustering of galaxies and quasars. Nature 435, 629–636 (2005)

    ADS  CAS  Article  Google Scholar 

  2. Kampakoglou, M., Trotta, R. & Silk, J. Monolithic or hierarchical star formation? A new statistical analysis. Mon. Not. R. Astron. Soc. 384, 1414–1426 (2008)

    ADS  CAS  Article  Google Scholar 

  3. van Dokkum, P. G. et al. Confirmation of the remarkable compactness of massive quiescent galaxies at z ≈ 2.3: early-type galaxies did not form in a simple monolithic collapse. Astrophys. J. Lett. 677, L5–L8 (2008)

    ADS  Article  Google Scholar 

  4. De Lucia, G. & Blaizot, J. The hierarchical formation of the brightest cluster galaxies. Mon. Not. R. Astron. Soc. 375, 2–14 (2007)

    ADS  Article  Google Scholar 

  5. Bower, R. G. et al. Breaking the hierarchy of galaxy formation. Mon. Not. R. Astron. Soc. 370, 645–655 (2006)

    ADS  CAS  Article  Google Scholar 

  6. Vale, A. & Ostriker, J. P. A non-parametric model for linking galaxy luminosity with halo/subhalo mass: are brightest cluster galaxies special? Mon. Not. R. Astron. Soc. 383, 355–368 (2008)

    ADS  CAS  Article  Google Scholar 

  7. Sandage, A. & Hardy, E. The redshift-distance relation. VIL absolute magnitudes of the first three ranked cluster galaxies as functions of cluster richness and Bautz-Morgan cluster type: the effect of q o . Astrophys. J. 183, 743–758 (1973)

    ADS  Article  Google Scholar 

  8. Lauer, T. R. & Postman, M. The motion of the Local Group with respect to the 15,000 kilometer per second Abell cluster inertial frame. Astrophys. J. 425, 418–438 (1994)

    ADS  Article  Google Scholar 

  9. Collins, C. A. & Mann, R. G. The K-band Hubble diagram for brightest cluster galaxies in X-ray clusters. Mon. Not. R. Astron. Soc. 297, 128–142 (1998)

    ADS  Article  Google Scholar 

  10. Burke, D. J., Collins, C. A. & Mann, R. G. Cluster selection and the evolution of brightest cluster galaxies. Astrophys. J. Lett. 532, L105–L108 (2000)

    ADS  CAS  Article  Google Scholar 

  11. Bremer, M. N. et al. XMM-LSS discovery of a z = 1.22 galaxy cluster. Mon. Not. R. Astron. Soc. 371, 1427–1434 (2006)

    ADS  CAS  Article  Google Scholar 

  12. Stanford, S. A. et al. The XMM Cluster Survey: a massive galaxy cluster at z = 1.45. Astrophys. J. Lett. 646, L13–L16 (2006)

    ADS  CAS  Article  Google Scholar 

  13. Rosati, P. et al. An X-ray-selected galaxy cluster at Z = 1.26. Astron. J. 118, 76–85 (1999)

    ADS  CAS  Article  Google Scholar 

  14. Demarco, R. et al. VLT and ACS observations of RDCS J1252.9–2927: dynamical structure and galaxy populations in a massive cluster at z = 1.237. Astrophys. J. 663, 164–182 (2007)

    ADS  CAS  Article  Google Scholar 

  15. Mullis, C. R. et al. Discovery of an X-ray-luminous galaxy cluster at z = 1.4. Astrophys. J. Lett. 623, L85–L88 (2005)

    ADS  CAS  Article  Google Scholar 

  16. Romer, A. K., Viana, P. T. P., Liddle, A. R. & Mann, R. G. A serendipitous galaxy cluster survey with XMM: expected catalog properties and scientific applications. Astrophys. J. 547, 594–608 (2001)

    ADS  Article  Google Scholar 

  17. Sahlén, M. et al. The XMM Cluster Survey: forecasting cosmological and cluster scaling relation parameter constraints. Preprint at 〈〉 (2008)

  18. Hilton, M. et al. The XMM Cluster Survey: the dynamical state of XMMXCS J2215.9–1738 at z = 1.457. Astrophys. J. 670, 1000–1009 (2007)

    ADS  CAS  Article  Google Scholar 

  19. Stott, J. P., Edge, A. C., Smith, G. P., Swinbank, A. M. & Ebeling, H. Near-infrared evolution of brightest cluster galaxies in the most X-ray luminous clusters since z = 1. Mon. Not. R. Astron. Soc. 384, 1502–1510 (2008)

    ADS  CAS  Article  Google Scholar 

  20. Whiley, I. M. et al. The evolution of the brightest cluster galaxies since z ≈ 1 from the ESO Distant Cluster Survey (EDisCS). Mon. Not. R. Astron. Soc. 387, 1253–1263 (2008)

    ADS  Article  Google Scholar 

  21. Yamada, T. et al. Witnessing the hierarchical assembly of the brightest cluster galaxy in a cluster at z = 1.26. Astrophys. J. Lett. 577, L89–L92 (2002)

    ADS  Article  Google Scholar 

  22. Eggen, O. J., Lynden-Bell, D. & Sandage, A. R. Evidence from the motions of old stars that the Galaxy collapsed. Astrophys. J. 136, 748–767 (1962)

    ADS  Article  Google Scholar 

  23. Larson, R. B. Dynamical models for the formation and evolution of spherical galaxies. Mon. Not. R. Astron. Soc. 166, 585–616 (1974)

    ADS  Article  Google Scholar 

  24. Binney, J. On the origin of the galaxy luminosity function. Mon. Not. R. Astron. Soc. 347, 1093–1096 (2004)

    ADS  CAS  Article  Google Scholar 

  25. Dekel, A. et al. Cold streams in early massive hot haloes as the main mode of galaxy formation. Nature 457, 451–454 (2009)

    ADS  CAS  Article  Google Scholar 

  26. Wake, D. A. et al. The 2df SDSS LRG and QSO survey: evolution of the luminosity function of luminous red galaxies to z = 0.6. Mon. Not. R. Astron. Soc. 372, 537–550 (2006)

    ADS  Article  Google Scholar 

  27. Almeida, C. et al. Luminous red galaxies in hierarchical cosmologies. Mon. Not. R. Astron. Soc. 386, 2145–2160 (2008)

    ADS  Article  Google Scholar 

  28. Lin, Y.-T. & Mohr, J. J. K-band properties of galaxy clusters and groups: brightest cluster galaxies and intracluster light. Astrophys. J. 617, 879–895 (2004)

    ADS  CAS  Article  Google Scholar 

  29. Bruzual, G. & Charlot, S. Stellar population synthesis at the resolution of 2003. Mon. Not. R. Astron. Soc. 344, 1000–1028 (2003)

    ADS  Article  Google Scholar 

  30. Chabrier, G. Galactic stellar and substellar initial mass function. Publ. Astron. Soc. Pacif. 115, 763–795 (2003)

    ADS  Article  Google Scholar 

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This work is based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan and the XMM-Newton, an ESA science mission funded by contributions from ESA member states and from NASA. We acknowledge financial support from Liverpool John Moores University and the STFC. M.H. acknowledges support from the South African National Research Foundation. IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. We thank G. De Lucia for making simulation results available to us in tabular form, I. Tanaka for developing the MCSRED package used to reduce the MOIRCS data, M. Salaris for discussions on stellar population synthesis models and B. Maughan for discussions on cluster masses.

Author Contributions C.A.C. provided the scientific leadership, helped design the experiment, wrote the paper and led the interpretation. J.P.S. performed the photometry and data analysis and made major contributions to the interpretation. M.H. wrote the Subaru proposal, carried out the data reduction and photometric calibration, contributed to the analysis and interpretation and provided detailed comments on the manuscript. S.T.K. independently checked the cluster mass calculations. S.A.S. provided useful discussions on the data and comments on the manuscript. The remaining authors make up the team of the wider XCS project which led to the discovery of J2215. R.G.M., R.C.N., and A.K.R. made useful comments on the text.

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Correspondence to Chris A. Collins.

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Collins, C., Stott, J., Hilton, M. et al. Early assembly of the most massive galaxies. Nature 458, 603–606 (2009).

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