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.

  • Article
  • Published:

A population of red candidate massive galaxies ~600 Myr after the Big Bang


Galaxies with stellar masses as high as roughly 1011 solar masses have been identified1,2,3 out to redshifts z of roughly 6, around 1 billion years after the Big Bang. It has been difficult to find massive galaxies at even earlier times, as the Balmer break region, which is needed for accurate mass estimates, is redshifted to wavelengths beyond 2.5 μm. Here we make use of the 1–5 μm coverage of the James Webb Space Telescope early release observations to search for intrinsically red galaxies in the first roughly 750 million years of cosmic history. In the survey area, we find six candidate massive galaxies (stellar mass more than 1010 solar masses) at 7.4 ≤ z ≤ 9.1, 500–700 Myr after the Big Bang, including one galaxy with a possible stellar mass of roughly 1011 solar masses. If verified with spectroscopy, the stellar mass density in massive galaxies would be much higher than anticipated from previous studies on the basis of rest-frame ultraviolet-selected samples.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Redshifts and tentative stellar masses of double-break selected galaxies.
Fig. 2: Images of the six galaxies with the highest apparent masses as a function of wavelength.
Fig. 3: SEDs and stellar population model fits.
Fig. 4: Cumulative stellar mass density, if the fiducial masses of the JWST-selected red galaxies are confirmed.

Similar content being viewed by others

Data availability

The HST data are available in the MAST (, under program ID 1345. Photometry, EAZY template set, fiducial redshifts and stellar masses of the sources presented here are available at

Code availability

Publicly available codes and standard data reduction tools in the Python environments were used: Grizli4, EAZY5, astropy63, photutils64 and Prospector17,36,37.


  1. Glazebrook, K. et al. A massive, quiescent galaxy at a redshift of 3.717. Nature 544, 71–74 (2017).

    Article  ADS  CAS  PubMed  Google Scholar 

  2. Riechers, D. A. et al. Rise of the Titans: gas excitation and feedback in a binary hyperluminous dusty starburst galaxy at z ~ 6. Astrophys. J. 907, 62 (2021).

    Article  ADS  CAS  Google Scholar 

  3. Stefanon, M. et al. Galaxy stellar mass functions from z ~ 10 to z ~ 6 using the deepest Spitzer/infrared array camera data: no significant evolution in the stellar-to-halo mass ratio of galaxies in the first gigayear of cosmic time. Astrophys. J. 922, 29 (2021).

    Article  ADS  CAS  Google Scholar 

  4. Brammer, G. & Matharu, J. gbrammer/grizli: Release 2021. Zenodo (2021).

  5. Schaerer, D. & de Barros, S. The impact of nebular emission on the ages of z ≈ 6 galaxies. Astron. Astrophys. 502, 423–426 (2009).

    Article  ADS  CAS  Google Scholar 

  6. Shim, H. et al. z ~ 4 Hα emitters in the great observatories origins deep survey: tracing the dominant mode for growth of galaxies. Astrophys. J. 738, 69 (2011).

    Article  ADS  Google Scholar 

  7. Labbé, I. et al. The spectral energy distributions of z ~ 8 galaxies from the IRAC ultra deep fields: emission lines, stellar masses, and specific star formation rates at 650 Myr. Astrophys. J. 777, L19 (2013).

    Article  ADS  Google Scholar 

  8. Stark, D. P. et al. Keck spectroscopy of 3. Astrophys. J. 763, 129 (2013).

    Article  ADS  Google Scholar 

  9. Smit, R. et al. Evidence for ubiquitous high-equivalent-width nebular emission in z ~ 7 galaxies: toward a clean measurement of the specific star-formation rate using a sample of bright, magnified galaxies. Astrophys. J. 784, 58 (2014).

    Article  ADS  Google Scholar 

  10. Smit, R. et al. High-precision photometric redshifts from Spitzer/IRAC: extreme [3.6]–[4.5] colors identify galaxies in the redshift range z ~ 6.6–6.9. Astrophys. J. 801, 122 (2015).

    Article  ADS  Google Scholar 

  11. Faisst, A. L. et al. A coherent study of emission lines from broadband photometry: specific star formation rates and [O III]/Hβ ratio at 3 < z < 6. Astrophys. J. 821, 122 (2016).

    Article  ADS  Google Scholar 

  12. De Barros, S. et al. The GREATS Hβ + [O III] luminosity function and galaxy properties at z ~ 8: walking the way of JWST. Mon. Not. R. Astron. Soc. 489, 2355–2366 (2019).

    Article  ADS  Google Scholar 

  13. Naidu, R. P. et al. Two remarkably luminous galaxy candidates at z ≈ 10–12 revealed by JWST. Astrophys. J. 940, L14 (2022).

    Article  ADS  Google Scholar 

  14. Endsley, R. et al. A JWST/NIRCam study of key contributors to reionization: the star-forming and ionizing properties of UV-faint z ~ 7–8 galaxies. Preprint at (2022).

  15. Stefanon, M. et al. Blue rest-frame UV-optical colors in z~8 galaxies from GREATS: very young stellar populations at 650 Myr of cosmic time. Astrophys. J. 927, 48 (2022).

    Article  ADS  Google Scholar 

  16. Brammer, G. B., van Dokkum, P. G. & Coppi, P. EAZY: a fast, public photometric redshift code. Astrophys. J. 686, 1503–1513 (2008).

    Article  ADS  Google Scholar 

  17. Leja, J., Johnson, B. D., Conroy, C., van Dokkum, P. G. & Byler, N. Deriving physical properties from broadband photometry with Prospector: description of the model and a demonstration of its accuracy using 129 galaxies in the local universe. Astrophys. J. 837, 170 (2017).

    Article  ADS  Google Scholar 

  18. Smit, R. et al. Inferred Hα flux as a star formation rate indicator at z ~ 4–5: implications for dust properties, burstiness, and the z = 4–8 star formation rate functions. Astrophys. J. 833, 254 (2016).

    Article  ADS  Google Scholar 

  19. Barro, G. et al. CANDELS: the progenitors of compact quiescent galaxies at z ~ 2. Astrophys. J. 765, 104 (2013).

    Article  ADS  Google Scholar 

  20. Roberts-Borsani, G. et al. Interpreting the Spitzer/IRAC colours of 7 ≤ z ≤ 9 galaxies: distinguishing between line emission and starlight using ALMA. Astrophys. J. 497, 3440 (2020).

    CAS  Google Scholar 

  21. Laporte, N. et al. Probing cosmic dawn: ages and star formation histories of candidate z ≥ 9 galaxies. Mon. Not. R. Astron. Soc. 505, 3336–3346 (2021).

    Article  ADS  Google Scholar 

  22. Topping, M. W. et al. The ALMA REBELS Survey: specific star formation rates in the reionization era. Mon. Not. R. Astron. Soc. 516, 975–991 (2022).

  23. Whitler, L. et al. Star formation histories of UV-luminous galaxies at z 6.8: implications for stellar mass assembly at early cosmic times. Mon. Not. R. Astron. Soc. 519, 5859–5881 (2023).

  24. Hashimoto, T. et al. The onset of star formation 250 million years after the Big Bang. Nature 557, 392 (2018).

    Article  ADS  CAS  PubMed  Google Scholar 

  25. Roberts-Borsani, G. et al. Improving z 7–11 galaxy property estimates with JWST/NIRCam medium-band photometry. Astrophys. J. 910, 86 (2021).

    Article  ADS  CAS  Google Scholar 

  26. Duncan, K. et al. The mass evolution of the first galaxies: stellar mass functions and star formation rates at 4 < z < 7 in the CANDELS GOODS-South field. Mon. Not. R. Astron. Soc. 444, 2960–2984 (2014).

    Article  ADS  Google Scholar 

  27. Davidzon, I. et al. The COSMOS2015 galaxy stellar mass function: thirteen billion years of stellar mass assembly in ten snapshots. Astron. Astrophys. 605, A70 (2017).

    Article  Google Scholar 

  28. Song, M. et al. The evolution of the galaxy stellar mass function at z = 4–8: a steepening low-mass-end slope with increasing redshift. Astrophys. J. 825, 5 (2016).

    Article  ADS  Google Scholar 

  29. Roberts-Borsani, G. W. et al. z 7 Galaxies with red spitzer/IRAC [3.6]–[4.5] colors in the full CANDELS data set: the brightest-known galaxies at z ~ 7–9 and a probable spectroscopic confirmation at z = 7.48. Astrophys. J. 823, 143 (2016).

  30. van Dokkum, P. G. et al. Dense cores in galaxies out to z = 2.5 in SDSS, UltraVISTA, and the five 3D-HST/CANDELS fields. Astrophys. J. 791, 45 (2014).

    Article  ADS  Google Scholar 

  31. Boylan-Kolchin, M. Stress testing ΛCDM with high-redshift galaxy candidates. Preprint at (2022).

  32. Menci, N. et al. High-redshift galaxies from early JWST observations: constraints on dark energy models. Astrophys. J. 938, L5 (2022).

    Article  ADS  Google Scholar 

  33. Finkelstein S. et al. CEERS key paper I: an early look into the first 500 Myr of galaxy formation with JWST. Preprint at (2022).

  34. Astropy Collaboration. The Astropy Project: sustaining and growing a community-oriented open-source project and the latest major release (v5.0) of the core package. Astrophys. J. 935, 167 (2022).

    Article  ADS  Google Scholar 

  35. Treu, T. et al. The initial mass function of early-type galaxies. Astrophys. J. 709, 1195 (2010).

    Article  ADS  Google Scholar 

  36. Bradley, L. et al. astropy/photutils: 1.5.0. Zenodo (2022).

  37. Boyer, M. L. et al. The JWST resolved stellar populations early release science program I.: NIRCam flux calibration. Preprint at (2022).

  38. Nardiello D. et al. Photometry and astrometry with JWST–I. NIRCam point spread functions and the first JWST colour-magnitude diagrams of a globular cluster. Preprint at (2022).

  39. Skelton, R. E. et al. 3D-HST WFC3-selected photometric catalogs in the five CANDELS/3D-HST fields: photometry, photometric redshifts, and stellar masses. Astrophys. J. Suppl. Ser. 214, 24 (2014).

  40. Kriek, M. et al. The MOSFIRE Deep Evolution Field (MOSDEF) survey: rest-frame optical spectroscopy for ~1500 H- selected galaxies at 1.37 < z < 3.8. Astrophys. J. Suppl. Ser. 218, 15 (2015).

  41. Zitrin, A. et al. Lyman-α emission from a luminous z = 8.68 galaxy: implications for galaxies as tracers of cosmic reionization. Astrophys. J. 810, L12 (2015).

    Article  ADS  Google Scholar 

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

  43. Cappellari, M. et al. Systematic variation of the stellar initial mass function in early-type galaxies. Nature 544, 485–488 (2012).

    Article  ADS  Google Scholar 

  44. Conroy, C. & van Dokkum, P. The stellar initial mass function in early-type galaxies from absorption line spectroscopy. II. Results. Astrophys. J. 760, 71 (2012).

    Article  ADS  Google Scholar 

  45. van Dokkum, P. et al. The stellar initial mass function in early-type galaxies from absorption line spectroscopy. III. Radial gradients. Astrophys. J. 841, 68 (2017).

    Article  ADS  Google Scholar 

  46. Schaerer, D. et al. First look with JWST spectroscopy: resemblance among z 8 galaxies and local analogs. Astron. Astrophys. 665, L4 (2022).

    Article  ADS  Google Scholar 

  47. Johnson, B. D., Leja, J., Conroy, C. & Speagle, J. S. Stellar population inference with prospector. Astrophys. J.S. 254, 22 (2021).

    Article  ADS  CAS  Google Scholar 

  48. Leja, J. et al. An older, more quiescent universe from panchromatic SED fitting of the 3D-HST survey. Astrophys. J. 877, 140 (2019).

    Article  ADS  CAS  Google Scholar 

  49. Choi, J. et al. Mesa isochrones and stellar tracks (MIST). I. Solar-scaled models. Astrophys. J. 823, 102 (2016).

    Article  ADS  Google Scholar 

  50. Dotter, A. MESA isochrones and stellar tracks (MIST) 0: methods for the construction of stellar isochrones. Astrophys. J. Suppl. Ser. 222, 8 (2016).

  51. Conroy, C., Gunn, J. E. & White, M. The propagation of uncertainties in stellar population synthesis modeling. I. The relevance of uncertain aspects of stellar evolution and the initial mass function to the derived physical properties of galaxies. Astrophys. J. 699, 486 (2009).

    Article  ADS  Google Scholar 

  52. Conroy, C. & Gunn, J. E. The propagation of uncertainties in stellar population synthesis modeling. III. Model calibration, comparison, and evaluation. Astrophys. J. 712, 833 (2010).

    Article  ADS  CAS  Google Scholar 

  53. Leja, J., Carnall, A. C., Johnson, B. D., Conroy, C. & Speagle, J. S. How to measure galaxy star formation histories. II. Nonparametric models. Astrophys. J. 876, 3 (2019).

    Article  ADS  CAS  Google Scholar 

  54. Byler, N., Dalcanton, J. J., Conroy, C. & Johnson, B. D. Nebular continuum and line emission in stellar population synthesis models. Astrophys. J. 840, 44 (2017).

    Article  ADS  Google Scholar 

  55. Speagle, J. DYNESTY: a dynamic nested sampling package for estimating Bayesian posteriors and evidences. Mon. Not. R. Astron. Soc. 493, 3132–3158 (2020).

    Article  ADS  Google Scholar 

  56. Leja, J. et al. A new census of the 0.2. Astrophys. J. 893, 111 (2020).

    Article  ADS  CAS  Google Scholar 

  57. Wang, B. et al. Inferring more from less: Prospector as a photometric redshift engine in the era of JWST. Astrophys. J. 944, L58 (2023).

  58. Bell, E. & de Jong, R. Stellar mass-to-light ratios and the Tully-Fisher relation. Astrophys. J. 550, 1 (2001).

    Article  Google Scholar 

  59. Carnall, A. et al. Inferring the star formation histories of massive quiescent galaxies with BAGPIPES: evidence for multiple quenching mechanisms. Mon. Not. R. Astron. Soc. 480, 4379–4401 (2018).

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  Google Scholar 

  61. Feroz, F. et al. Importance nested sampling and the MultiNest algorithm. Open J. of Astrophys. 2, 10 (2019).

    Article  ADS  Google Scholar 

  62. Salim, S., Boquien, M. & Lee, J. C. Dust attenuation curves in the local universe: demographics and new laws for star-forming galaxies and high-redshift analogs. Astrophys. J. 859, 11 (2018).

  63. Chevallard, J. et al. Insights into the content and spatial distribution of dust from the integrated spectral properties of galaxies. Mon. Not. R. Astron. Soc. 432, 2061 (2013).

    Article  ADS  Google Scholar 

  64. Steinhardt. C. L. et al. Templates for fitting photometry of ultra-high-redshift galaxies. Preprint at (2022).

  65. Trenti, M. & Stiavelli, M. Cosmic variance and its effect on the luminosity function determination in deep high-z surveys. Astrophys. J. 676, 767–780 (2008).

    Article  ADS  Google Scholar 

Download references


We are grateful to the CEERS team for providing these exquisite public JWST data so early in the mission. We thank M. Boylan-Kolchin for helpful discussions on the theoretical context of this work. Cloud-based data processing and file storage for this work is provided by the AWS Cloud Credits for Research program. The Cosmic DAWN Center is funded by the Danish National Research Foundation. K.W. wishes to acknowledge funding from Alfred P. Sloan Foundation grant no. FG-2019-12514. M.S. acknowledges project no. PID2019-109592GB-I00/AEI/10.13039/501100011033 from the Spanish Ministerio de Ciencia e Innovacion - Agencia Estatal de Investigacion.

Author information

Authors and Affiliations



I.L. performed the photometry, devised the selection method and led the analysis. P.v.D. drafted the main text. I.L. wrote the Methods section and produced the figures. G.B. developed the image processing pipeline and created the image mosaics. E.N. and R.B. identified the first double-break galaxy, prompting the systematic search for these objects. J.L., B.W., K.A.S. and E.M. ran the Prospector analysis. All authors contributed to the manuscript and aided the analysis and interpretation.

Corresponding author

Correspondence to Ivo Labbé.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature thanks James Dunlop and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Additional information

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

Extended data figures and tables

Extended Data Fig. 1 Systematic offsets in photometry as a function of wavelength.

The offsets are estimated by the ratio of the observed fluxes to the EAZY best-fit model fluxes for 5,000–10,000 sources at 0.1 < z < 5 in the CEERS field. The offsets are calculated separately for each detector (1–4), module (A/B), and filter. Symbols are slightly spread out in wavelength for clarity. a. The first in-flight NIRCam flux calibration update of 29 July 2022 (jwst_0942.pmap) introduced significant offsets in NIRCam short-wavelength zeropoints. b. After adopting our fiducial zeropoints, residual offsets are ~<3% across all bands. This paper adopts a 5% minimum systematic error for all photometric redshift and stellar population fits.

Extended Data Fig. 2 Images of the seven galaxies with apparent lowest mass.

The galaxies satisfy the color-color selection and have fiducial masses log(M*/M) < 10. The layout and panels of the figure are identical to Fig. 2 in the main text. Each cutout has a size of 2.4″ × 2.4″. The filters range from the 0.6 μm F606W filter of HST/ACS to the 4.4 μm F444W JWST/NIRCam filter.

Extended Data Fig. 3 Spectral energy distributions of all 13 galaxies that satisfy the color-color selection.

a.The layout of the figure is identical to Fig. 3a in the main text. In addition, an alternative model fit (model E, see Methods) is shown that produces low stellar masses (blue), but generally requires extremely young ages (<5 Myr) at specific narrow redshift intervals. b.The panel at the lower right shows the averaged rest-frame SED of the seven galaxies with fiducial log(M*/M) < 10, compared to previously-found galaxies at similar redshifts (see Fig. 3).


Extended Data Fig. 4 Results of the stellar population fitting.

Masses (a), redshifts (b), and the chi-squared fit quality (c) of the 13 galaxies that satisfy the color-color selection. For each galaxy seven different measurements are shown, as well as the median of the seven that is adopt as the fiducial value (see Methods section). These medians are listed in Extended Data Table 2.

Extended Data Fig. 5 Color difference between emission line and continuum-dominated models.

The line-dominated model is a 5 Myr old constant SFH with nebular emission lines. The continuum dominated model is a 50 Myr old CSF without emission lines. Two colors differences involving the line-sensitive F410M filter are shown: F356W-F410M (green) and F410M-F444W (red) and the sum of their absolute values. When Hα and Hβ+[OIII] move through the filters with redshift, the emission line sensitive medium-band F410M filter produces a strong signature, except at z = 5.6, 6.9, 7.7, where the lines transition between filters. Here continuum and line-dominated SEDs produce similar colors due to undersampling of the SED by the filters.

Extended Data Fig. 6 Stacked redshift probability distribution of all 13 galaxies in the sample.

The P(z) were derived using Bagpipes (as described in Methods). Redshifts of a high mass solution are shown in red (model B: Salim dust attenuation law, rising SFH, linear age prior, continuum dominated) and a low mass solution are shown in blue (model E: SMC dust, logarithmic age prior, emission line dominated). Other high mass fits (e.g., Prospector, EAZY) and low mass fits produce similar P(z). Solid curves show expected selection function under the assumption of continuum (red) or line-dominated models (blue). The high-mass continuum-dominated P(z) broadly traces the expected selection functions. The low-mass line-dominated P(z) is not expected for selection of a line-dominated model. The P(z) is concentrated at narrow redshifts around z = 5.6, 6.9, 7.7 (black dotted lines) where the line-sensitive F410M cannot distinguish between continuum and strong lines due to aliasing.

Extended Data Table 1 HST/ACS and JWST/NIRCam Photometry of the double break sample
Extended Data Table 2 Fiducial redshifts and stellar masses of the double break sample

Supplementary information

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Labbé, I., van Dokkum, P., Nelson, E. et al. A population of red candidate massive galaxies ~600 Myr after the Big Bang. Nature 616, 266–269 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


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