Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A massive protocluster of galaxies at a redshift of z ≈ 5.3


Massive clusters of galaxies have been found that date from as early as 3.9 billion years1 (3.9 Gyr; z = 1.62) after the Big Bang, containing stars that formed at even earlier epochs2,3. Cosmological simulations using the current cold dark matter model predict that these systems should descend from ‘protoclusters’—early overdensities of massive galaxies that merge hierarchically to form a cluster4,5. These protocluster regions themselves are built up hierarchically and so are expected to contain extremely massive galaxies that can be observed as luminous quasars and starbursts4,5,6. Observational evidence for this picture, however, is sparse because high-redshift protoclusters are rare and difficult to observe6,7. Here we report a protocluster region that dates from 1 Gyr (z = 5.3) after the Big Bang. This cluster of massive galaxies extends over more than 13 megaparsecs and contains a luminous quasar as well as a system rich in molecular gas8. These massive galaxies place a lower limit of more than 4 × 1011 solar masses of dark and luminous matter in this region, consistent with that expected from cosmological simulations for the earliest galaxy clusters4,5,7.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Spectra of confirmed cluster members.
Figure 2: Image of the region around the protocluster core.
Figure 3: Detail of the protocluster core.


  1. 1

    Larson, D. et al. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: power spectra and WMAP-derived parameters. Astrophys. J. Suppl. Ser. (in the press); preprint at 〈〉 (2010)

  2. 2

    Papovich, C. et al. A Spitzer-selected galaxy cluster at z = 1.62. Astrophys. J. 716, 1503–1513 (2010)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Mei, S. et al. Evolution of the color-magnitude relation in galaxy clusters at z 1 from the ACS Intermediate Redshift Cluster Survey. Astrophys. J. 690, 42–68 (2009)

    ADS  CAS  Article  Google Scholar 

  4. 4

    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 

  5. 5

    Li, Y. et al. Formation of z 6 quasars from hierarchical galaxy mergers. Astrophys. J. 665, 187–208 (2007)

    ADS  Article  Google Scholar 

  6. 6

    Overzier, R. et al. Stellar masses of Lyman break galaxies, Lyα emitters, and radio galaxies in overdense regions at z = 4–6. Astrophys. J. 704, 548–563 (2009)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Overzier, R. et al. ΛCDM predictions for galaxy protoclusters - I. The relation between galaxies, protoclusters and quasars at z 6. Mon. Not. R. Astron. Soc. 394, 577–594 (2009)

    ADS  Article  Google Scholar 

  8. 8

    Riechers, D. et al. A massive molecular gas reservoir in the z = 5.3 submillimeter galaxy AzTEC-3. Astrophys. J. Lett. 720, 131–136 (2010)

    ADS  Article  Google Scholar 

  9. 9

    Robertson, B. et al. Photometric properties of the most massive high-redshift galaxies. Astrophys. J. 667, 60–78 (2007)

    ADS  Article  Google Scholar 

  10. 10

    Miley, G. K. et al. A large population of ‘Lyman-break’ galaxies in a protocluster at redshift z ≈ 4.1. Nature 427, 47–50 (2004)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Walter, F. et al. Molecular gas in the host galaxy of a quasar at redshift z = 6.42. Nature 424, 406–408 (2003)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Wang, R. et al. Molecular gas in z ≈ 6 quasar host galaxies. Astrophys. J. 714, 699–712 (2010)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Scoville, N. Z. et al. The Cosmic Evolution Survey (COSMOS): overview. Astrophys. J. Suppl. Ser. 172, 1–8 (2007)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Scott, K. S. et al. AzTEC millimetre survey of the COSMOS field - I. Data reduction and source catalogue. Mon. Not. R. Astron. Soc. 385, 2225–2238 (2008)

    ADS  Article  Google Scholar 

  15. 15

    Younger, J. D. et al. Evidence for a population of high-redshift submillimeter galaxies from interferometric imaging. Astrophys. J. 671, 1531–1537 (2007)

    ADS  Article  Google Scholar 

  16. 16

    Schinnerer, E. et al. The VLA-COSMOS Survey. II. Source catalog of the large project. Astrophys. J. Suppl. Ser. 172, 46–69 (2007)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Elvis, M. et al. The Chandra COSMOS Survey. I. Overview and point source catalog. Astrophys. J. 184, 158–171 (2009)

    CAS  Article  Google Scholar 

  18. 18

    Kennicutt, J. Star formation in galaxies along the Hubble sequence. Annu. Rev. Astron. Astrophys. 36, 189–232 (1998)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Bouwens, R. J., Illingworth, G. D., Franx, M. & Ford, H. UV luminosity functions at z 4, 5, and 6 from the Hubble Ultra Deep Field and other deep Hubble Space Telescope ACS fields: evolution and star formation history. Astrophys. J. 670, 928–958 (2007)

    ADS  CAS  Article  Google Scholar 

  20. 20

    Hildebrandt, H. et al. CARS: the CFHTLS-Archive-Research Survey. II. Weighing dark matter halos of Lyman-break galaxies at z = 3–5. Astron. Astrophys. 498, 725–736 (2009)

    ADS  Article  Google Scholar 

  21. 21

    Capak, P. et al. The first release COSMOS optical and near-IR data and catalog. Astrophys. J. Suppl. Ser. 172, 99–116 (2007)

    ADS  Article  Google Scholar 

  22. 22

    Brusa, M. et al. High-redshift quasars in the COSMOS survey: the space density of z > 3 X-ray selected QSOs. Astrophys. J. 693, 8–22 (2009)

    ADS  CAS  Article  Google Scholar 

  23. 23

    Stark, D. P. et al. The evolutionary history of Lyman break galaxies between redshift 4 and 6: observing successive generations of massive galaxies in formation. Astrophys. J. 697, 1493–1511 (2009)

    ADS  Article  Google Scholar 

  24. 24

    Maraston, C. Evolutionary synthesis of stellar populations: a modular tool. Mon. Not. R. Astron. Soc. 300, 872–892 (1998)

    ADS  Article  Google Scholar 

  25. 25

    Calzetti, D., Kinney, A. L. & Storchi-Bergmann, T. Dust obscuration in starburst galaxies from near-infrared spectroscopy. Astrophys. J. 458, 132–135 (1996)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Pettini, M., Steidel, C. C., Adelberger, K. L., Dickinson, M. & Giavalisco, M. The ultraviolet spectrum of MS 1512–CB58: an insight into Lyman-break galaxies. Astrophys. J. 528, 96–107 (2000)

    ADS  CAS  Article  Google Scholar 

  27. 27

    Tacconi, L. et al. High molecular gas fractions in normal massive star-forming galaxies in the young Universe. Nature 463, 781–784 (2010)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Tacconi, L. J. et al. Submillimeter galaxies at z 2: evidence for major mergers and constraints on lifetimes, IMF, and CO-H2 conversion factor. Astrophys. J. 680, 246–262 (2008)

    ADS  CAS  Article  Google Scholar 

Download references


These results are based on observations with: the W. M. Keck Observatory, the IRAM Plateau de Bure Interferometer, the IRAM 30-m telescope with the GISMO 2-mm camera, the Chandra X-ray Observatory, the Subaru Telescope, the Hubble Space Telescope, the Canada-France-Hawaii Telescope with WIRCam and MegaPrime, the United Kingdom Infrared Telescope, the Spitzer Space Telescope, the Smithsonian Submillimeter Array Telescope, the James Clerk Maxwell Telescope with the AzTEC 1.1mm camera, and the National Radio Astronomy Observatory’s Very Large Array. D.R. and B.R. acknowledge support from NASA through Hubble Fellowship grants awarded by the Space Telescope Science Institute. P.L.C. and N.Z.S. acknowledge grant support from NASA. G.W.W., M.Y. and J.G.S. acknowledge grant support from the NSF.

Author information




P.L.C. led the spectroscopic effort, reduced the spectroscopic and photometric data, and led the scientific analysis including the optical and radio/millimetre fitting analysis and cluster properties. N.Z.S. led the spectroscopic and photometric follow-up efforts. D.R., C.C., P.C. and R.N. assisted with the physical interpretation of the radio data. B.R. provided cosmological simulations to check the significance of the protocluster and the likelihood of finding it. M.S., L.Y., M.E., F.C. and B.M. carried out the Keck observations and assisted with the data reduction. E.S. reduced and analysed the radio data. G.W.W. and M.Y. assisted with the submillimetre data analysis. F.C. and M.E. assisted with the X-ray data analysis. A.K. coordinated the 2-mm observations. J.G.S. conducted and reduced the 2-mm observations.

Corresponding author

Correspondence to Peter L. Capak.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

The file contains Supplementary Text, Supplementary Figures 1-2 with legends, Supplementary Tables 1-2 and additional references. (PDF 1206 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Capak, P., Riechers, D., Scoville, N. et al. A massive protocluster of galaxies at a redshift of z ≈ 5.3. Nature 470, 233–235 (2011).

Download citation

Further reading

  • First constraints on the AGN X-ray luminosity function at z ~ 6 from an eROSITA-detected quasar

    • J. Wolf
    • , K. Nandra
    • , M. Salvato
    • , T. Liu
    • , J. Buchner
    • , M. Brusa
    • , D. N. Hoang
    • , V. Moss
    • , R. Arcodia
    • , M. Brüggen
    • , J. Comparat
    • , F. de Gasperin
    • , A. Georgakakis
    • , A. Hotan
    • , G. Lamer
    • , A. Merloni
    • , A. Rau
    • , H. J. A. Rottgering
    • , T. W. Shimwell
    • , T. Urrutia
    • , M. Whiting
    •  & W. L. Williams

    Astronomy & Astrophysics (2021)

  • The environment of QSO triplets at 1 ≲ z ≲ 1.5

    • Marcelo C Vicentin
    • , Pablo Araya-Araya
    • , Laerte Sodré
    • , Roderik Overzier
    • , Eleazar R Carrasco
    •  & Hector Cuevas

    Monthly Notices of the Royal Astronomical Society (2021)

  • Probing the existence of a rich galaxy overdensity at z = 5.2

    • Rosa Calvi
    • , Helmut Dannerbauer
    • , Pablo Arrabal Haro
    • , José M Rodríguez Espinosa
    • , Casiana Muñoz-Tuñón
    • , Pablo G Pérez González
    •  & Stefan Geier

    Monthly Notices of the Royal Astronomical Society (2021)

  • The ALPINE–ALMA [C II] survey

    • Federica Loiacono
    • , Roberto Decarli
    • , Carlotta Gruppioni
    • , Margherita Talia
    • , Andrea Cimatti
    • , Gianni Zamorani
    • , Francesca Pozzi
    • , Lin Yan
    • , Brian C. Lemaux
    • , Dominik A. Riechers
    • , Olivier Le Fèvre
    • , Matthieu Bèthermin
    • , Peter Capak
    • , Paolo Cassata
    • , Andreas Faisst
    • , Daniel Schaerer
    • , John D. Silverman
    • , Sandro Bardelli
    • , Médéric Boquien
    • , Sandra Burkutean
    • , Miroslava Dessauges-Zavadsky
    • , Yoshinobu Fudamoto
    • , Seiji Fujimoto
    • , Michele Ginolfi
    • , Nimish P. Hathi
    • , Gareth C. Jones
    • , Yana Khusanova
    • , Anton M. Koekemoer
    • , Guilaine Lagache
    • , Lori M. Lubin
    • , Marcella Massardi
    • , Pascal Oesch
    • , Michael Romano
    • , Livia Vallini
    • , Daniela Vergani
    •  & Elena Zucca

    Astronomy & Astrophysics (2021)

  • A Noncorotating Gas Component in an Extreme Starburst at z = 4.3

    • Ken-ichi Tadaki
    • , Daisuke Iono
    • , Min S. Yun
    • , Itziar Aretxaga
    • , Bunyo Hatsukade
    • , Minju M. Lee
    • , Tomonari Michiyama
    • , Kouichiro Nakanishi
    • , Toshiki Saito
    • , Junko Ueda
    •  & Hideki Umehata

    The Astrophysical Journal (2020)


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing