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A dusty, normal galaxy in the epoch of reionization


Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging1. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light2,3,4. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z ≥ 76,7,8. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 ± 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization9, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7.

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Figure 1: The gravitationally lensing galaxy cluster Abell 1689.
Figure 2: Spectrum of A1689-zD1.
Figure 3: ALMA SNR maps of A1689-zD1.


  1. Smit, R. et al. The star formation rate function for redshift z 4–7 galaxies: evidence for a uniform buildup of star-forming galaxies during the first 3 Gyr of cosmic time. Astrophys. J. 756, 14 (2012)

    Article  ADS  Google Scholar 

  2. Finkelstein, S. L. et al. A galaxy rapidly forming stars 700 million years after the Big Bang at redshift 7.51. Nature 502, 524–527 (2013)

    Article  ADS  CAS  PubMed  Google Scholar 

  3. Shibuya, T. et al. The first systematic survey for Lyα emitters at z = 7.3 with red-sensitive Subaru/Suprime-Cam. Astrophys. J. 752, 114 (2012)

    Article  ADS  CAS  Google Scholar 

  4. Treu, T. et al. The changing Lyα optical depth in the range 6 < z < 9 from the MOSFIRE spectroscopy of Y-dropouts. Astrophys. J. 775, L29 (2013)

    Article  ADS  CAS  Google Scholar 

  5. Magdis, G. E. et al. The molecular gas content of z = 3 Lyman break galaxies: evidence of a non-evolving gas fraction in main-sequence galaxies at z > 2. Astrophys. J. 758, L9 (2012)

    Article  ADS  CAS  Google Scholar 

  6. Tan, Q. et al. A deep search for molecular gas in two massive Lyman break galaxies at z = 3 and 4: vanishing CO-emission due to low metallicity? Astrophys. J. 776, L24 (2013)

    Article  ADS  CAS  Google Scholar 

  7. Fisher, D. B. et al. The rarity of dust in metal-poor galaxies. Nature 505, 186–189 (2014)

    Article  ADS  CAS  PubMed  Google Scholar 

  8. Ouchi, M. et al. An intensely star-forming galaxy at z 7 with low dust and metal content revealed by deep ALMA and HST observations. Astrophys. J. 778, 102 (2013)

    Article  ADS  CAS  Google Scholar 

  9. Bouwens, R. J. et al. UV luminosity functions at redshifts z 4 to z 10: 11000 galaxies from HST legacy fields. Astrophys. J. (in the press); preproof at (2014)

  10. Bradley, L. D. et al. Discovery of a very bright strongly lensed galaxy candidate at z 7.6. Astrophys. J. 678, 647–654 (2008)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  Google Scholar 

  12. da Cunha, E. et al. On the effect of the cosmic microwave background in high-redshift sub-millimeter observations. Astrophys. J. 766, 13 (2013)

    Article  ADS  CAS  Google Scholar 

  13. Michałowski, M. J., Watson, D. & Hjorth, J. Rapid dust production in submillimeter galaxies at z > 4? Astrophys. J. 712, 942–950 (2010)

    Article  ADS  CAS  Google Scholar 

  14. Kennicutt, R. C. & Evans, N. J. Star formation in the Milky Way and nearby galaxies. Annu. Rev. Astron. Astrophys. 50, 531–608 (2012)

    Article  ADS  CAS  Google Scholar 

  15. Draine, B. et al. Dust masses, PAH abundances, and starlight intensities in the SINGS galaxy sample. Astrophys. J. 663, 866–894 (2007)

    Article  ADS  CAS  Google Scholar 

  16. Zafar, T. & Watson, D. The metals-to-dust ratio to very low metallicities using GRB and QSO absorbers; extremely rapid dust formation. Astron. Astrophys. 560, A26 (2013)

    Article  ADS  Google Scholar 

  17. Christensen, L. et al. The low-mass end of the fundamental relation for gravitationally lensed star-forming galaxies at 1 < z < 6. Mon. Not. R. Astron. Soc. 427, 1953–1972 (2012)

    Article  ADS  Google Scholar 

  18. 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  CAS  Google Scholar 

  19. Stark, D. P. et al. Ultraviolet emission lines in young low mass galaxies at z 2: physical properties and implications for studies at z > 7. Mon Not. R. Astron. Soc. 445, 3200–3220 (2014)

    Article  ADS  CAS  Google Scholar 

  20. Carilli, C. L. & Walter, F. Cool gas in high-redshift galaxies. Annu. Rev. Astron. Astrophys. 51, 105–161 (2013)

    Article  ADS  CAS  Google Scholar 

  21. Cooray, A. et al. HerMES: the rest-frame UV emission and a lensing model for the z = 6.34 luminous dusty starburst galaxy HFLS3. Astrophys. J. 790, 40 (2014)

    Article  ADS  CAS  Google Scholar 

  22. Hu, E. M. et al. A redshift z = 6.56 galaxy behind the cluster Abell 370. Astrophys. J. 568, L75–L79 (2002)

    Article  ADS  CAS  Google Scholar 

  23. Bradley, L. D. et al. Through the looking glass: bright, highly magnified galaxy candidates at z 7 behind A1703. Astrophys. J. 747, 3 (2012)

    Article  ADS  Google Scholar 

  24. Iye, M. et al. A galaxy at a redshift z = 6.96. Nature 443, 186–188 (2006)

    Article  ADS  CAS  PubMed  Google Scholar 

  25. Tanvir, N. et al. A γ-ray burst at a redshift of z 8.2. Nature 461, 1254–1257 (2009)

    Article  ADS  CAS  PubMed  Google Scholar 

  26. Schaerer, D. et al. New constraints on dust emission and UV attenuation of z = 6.5–7.5 galaxies from IRAM and ALMA observations. Astron. Astrophys. 574, A19 (2014)

    Article  Google Scholar 

  27. Jiang, L. et al. Physical properties of spectroscopically confirmed galaxies at z ≥ 6. I. Basic characteristics of the rest-frame UV continuum and Lyα emission. Astrophys. J. 772, 99 (2013)

    Article  ADS  CAS  Google Scholar 

  28. Ota, K. et al. ALMA observation of 158 μm [C ii] line and dust continuum of a z = 7 normally star-forming galaxy in the epoch of reionization. Astrophys. J. 792, 34 (2014)

    Article  ADS  CAS  Google Scholar 

  29. Berger, E. et al. ALMA observations of the host galaxy of GRB090423 at z = 8.23: deep limits on obscured star formation 630 million years after the Big Bang. Astrophys. J. (submitted); preprint at (2014)

  30. Tanvir, N. R. et al. Star formation in the early universe: beyond the tip of the iceberg. Astrophys. J. 754, 46 (2012)

    Article  ADS  Google Scholar 

  31. Christensen, L. et al. Gravitationally lensed galaxies at 2 < z < 3.5: direct abundance measurements of Lyα emitters. Mon. Not. R. Astron. Soc. 427, 1973–1982 (2012)

    Article  ADS  CAS  Google Scholar 

  32. Madau, P. Radiative transfer in a clumpy universe: the colors of high-redshift galaxies. Astrophys. J. 441, 18–27 (1995)

    Article  ADS  Google Scholar 

  33. Bolzonella, M., Miralles, J.-M. & Pelló, R. Photometric redshifts based on standard SED fitting procedures. Astron. Astrophys. 363, 476–492 (2000)

    ADS  CAS  Google Scholar 

  34. Kennicutt, R. C. Star formation in galaxies along the Hubble sequence. Annu. Rev. Astron. Astrophys. 36, 189–231 (1998)

    Article  ADS  CAS  Google Scholar 

  35. McMullin, J. P., Waters, B., Schiebel, D. & Young, W. in Astronomical Data Analysis Software And Systems XVI (eds Shaw, R. A., Hill, F. & Bell, D. J. ) Astron. Soc. Pacif. Conf. Ser. 376, 127–130 (2007)

    ADS  Google Scholar 

  36. Díaz-Santos, T. Explaining the [C ii]157.7 μm deficit in luminous infrared galaxies—first results from a Herschel/PACS study of the GOALS sample. Astrophys. J. 774, 68 (2013)

    Article  ADS  CAS  Google Scholar 

  37. Riechers, D. A. et al. A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34. Nature 496, 329–333 (2013)

    Article  ADS  CAS  Google Scholar 

  38. Andersen, A. C. in Why Galaxies Care About AGB Stars: their Importance as Actors And Probes (eds Kirschbaum, F. Charbonnel, C. & Wing, R. F. ) ASP Conf. Ser. 768, 170–180 (2007)

    Google Scholar 

  39. Meurer, G. R., Heckman, T. M. & Calzetti, D. Dust absorption and the ultraviolet luminosity density at z 3 as calibrated by local starburst galaxies. Astrophys. J. 521, 64–80 (1999)

    Article  ADS  CAS  Google Scholar 

  40. Oteo, I. Dust correction factors over 0 < z < 3 in massive star-forming galaxies from a stacking analysis of Herschel data. Astron. Astrophys. 572, L4 (2014)

    Article  ADS  Google Scholar 

  41. Komatsu, E. et al. Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: cosmological interpretation. Astrophys. J. 192 (Suppl.). 18 (2011)

    Article  Google Scholar 

  42. Koekemoer, A. M., Fruchter, A. S., Hook, R. N. & Hack, W. in The 2002 HST Calibration Workshop: HST after the Installation of the ACS and the NICMOS Cooling System (eds Arribas, S., Koekemoer, A. & Whitmore, B. ) 337–340 (Space Telescope Science Institute, 2003);

  43. 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 

  44. Charlot, S. & Fall, M. A simple model for the absorption of starlight by dust in galaxies. Astrophys. J. 539, 718–731 (2000)

    Article  ADS  CAS  Google Scholar 

  45. Gallazzi, A., Charlot, S., Brinchmann, J., White, S. D. M. & Tremonti, C. A. The ages and metallicities of galaxies in the local universe. Mon. Not. R. Astron. Soc. 362, 41–58 (2005)

    Article  ADS  CAS  Google Scholar 

  46. Salim, S. et al. New constraints on the star formation histories and dust attenuation of galaxies in the local Universe from GALEX. Astrophys. J. 619, L39–L42 (2005)

    Article  ADS  CAS  Google Scholar 

  47. da Cunha, E., Charlot, S. & Elbaz, D. A simple model to interpret the ultraviolet, optical and infrared emission from galaxies. Mon. Not. R. Astron. Soc. 388, 1595–1617 (2008)

    Article  ADS  CAS  Google Scholar 

  48. Silva, L., Granato, G. L., Bressan, A. & Danese, L. Modeling the effects of dust on galactic spectral energy distributions from the ultraviolet to the millimeter band. Astrophys. J. 509, 103–117 (1998)

    Article  ADS  CAS  Google Scholar 

  49. Iglesias-Páramo, J. et al. UV to IR SEDs of UV-selected galaxies in the ELAIS fields: evolution of dust attenuation and star formation activity from z = 0.7 to 0.2. Astrophys. J. 670, 279–294 (2007)

    Article  ADS  Google Scholar 

  50. Michałowski, M., Hjorth, J. & Watson, D. Cosmic evolution of submillimeter galaxies and their contribution to stellar mass assembly. Astron. Astrophys. 514, A67 (2010)

    Article  ADS  Google Scholar 

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The Dark Cosmology Centre is funded by the Danish National Research Foundation. L.C. is supported by the EU under a Marie Curie Intra-European Fellowship, contract number PIEF-GA-2010-274117. K.K. acknowledges support from the Swedish Research Council and the Knut and Alice Wallenberg Foundation. J.R. acknowledges support from a European Research Council starting grant, CALENDS, and the Career Integration Grant 294074. A.G. acknowledges support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 267251 (“AstroFIt”). M.J.M. acknowledges the support of the Science and Technology Facilities Council. ALMA is a partnership of the European Southern Observatory (ESO, representing its member states), the National Science Foundation (USA) and National Institutes of Natural Sciences (Japan), together with the National Research Council (Canada) and the National Science Council and the Academia Sinica Institute for Astronomy and Astrophysics (Taiwan), in cooperation with Chile. The Joint ALMA Observatory is operated by the ESO, Associated Universities Inc./National Radio Astronomy Observatory and the National Astronomical Observatory of Japan. We thank L. Lindroos, J. Hjorth, J. Fynbo, A. C. Andersen, and R. Bouwens for discussions, M. Limousin for providing a lensing map of the cluster, and the Nordic ALMA Regional Center Node for assistance.

Author information

Authors and Affiliations



D.W. conceived the study, was Principal Investigator of the X-shooter programme, produced Fig. 1 and Extended Data Figs 1 and 4–7 and wrote the main text. L.C. reduced and analysed the X-shooter spectrum, did the HyperZ analysis and produced Fig. 2 and Extended Data Fig. 2. K.K. reduced and analysed the ALMA data and produced Fig. 3 and Extended Data Fig. 3. J.R. was Principal Investigator of the ALMA programmes and reduced and analysed the Hubble data. A.G. modelled the ultraviolet SED and determined the galaxy stellar age. M.J.M. modelled the full ultraviolet–far-infrared SED and produced Table 1. All authors contributed to the Methods and all authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Darach Watson.

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The authors declare no competing financial interests.

Additional information

This paper makes use of the following ALMA data: ADS/JAO.ALMA 2011.0.00319.S and 2012.1.00261.S available from the ALMA archive at

Extended data figures and tables

Extended Data Figure 1 Cumulative sum of the unbinned spectrum.

The VIS and NIR arms are plotted in blue and red respectively. The best-fitting step function is plotted as a dashed line. The break in the spectrum is clearly detected with the NIR arm only. Gaps in the cumulative spectrum are due to removal of regions affected by strong sky absorption.

Extended Data Figure 2 Spectrum obtained only at position angle 64° East of North.

The slit consistently covered both the emission from the high redshift galaxy and the galaxy located 2″ below it. This spectrum uses approximately half of the total exposure time. The upper panel shows the two-dimensional rectified spectrum, the lower panel the one-dimensional spectrum of the companion. Error bars are 68% confidence. The spectrum of the companion galaxy is recovered through the entire spectral range, including that covered by the transition from the VIS to the NIR data, and shows no indication of the sharp break seen in A1689-zD1.

Extended Data Figure 3 Probability distribution as a function of redshift for galaxy template fits to the Hubble and Spitzer IRAC photometry data.

The probability distribution is based on fitting galaxies using the New-HyperZ code33.

Extended Data Figure 4 The tapered ALMA flux image at 226 GHz, centred on A1689-zD1; the image is primary-beam-corrected.

The depth of the map at the location of A1689-zD1is 0.12 mJy per beam (42% of the deepest part of the mosaic). The sensitivity decreases towards the edge of the mosaic owing to the overlap of multiple pointings and primary beam correction. The structure north of A1689-zD1 is a probable detection of a different source in the field and will be presented in a forthcoming paper (K.K. et al., manuscript in preparation).

Extended Data Figure 5 Dust mass and SFRTIR from modified blackbody fits.

Tracks show how the parameters change with temperature, with different tracks for different opacity wavelengths, λ0. Varying βIR is shown for λ0 = 200 µm (black and grey lines). Intrinsic (CMB-corrected) and measured temperatures are indicated for λ0 = 300 µm (orange line) on the concave and convex sides respectively. A diamond marks our fiducial model: uncorrected T = 35 K, λ0 = 200 µm, βIR = 1.92. Solid-colour regions show <90%, <95%, and <99% confidence intervals due to the βUV–IRX relation (including measurement uncertainties, βIR = 1.72–2.12, and λ0 < 300 µm), with solid, dashed, and dot-dashed lines indicating these intervals for the tracks. Dotted lines mark >99%.

Extended Data Figure 6 Ultraviolet–optical SED for A1689-zD1.

Stellar synthesis models from ref. 43 (BC03) are fitted to the photometric data (squares). Error bars are 68% confidence. The best-fitting model is shown in green with the resultant fluxes in the different bands shown as circles. The Very Large Telescope (VLT)/X-shooter spectrum is also plotted (solid histogram) for comparison.

Extended Data Figure 7 SED of A1689-zD1.

Full, self-consistent ultraviolet-to-far-infrared models are fitted to the data using the GRASIL (dashed line) and MAGPHYS (dash-dotted line) codes. The values derived from these models fitted to the photometric data (squares) are largely consistent with those derived from the modified blackbody (solid line) and ultraviolet–optical-only fit, though with an additional contribution from the restframe mid-infrared flux. A CMB correction has not been applied here. Error bars are 68% confidence. Upper limits are 68% confidence for all points except the 8.0-µm band, for which the upper limit is 95% confidence.

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Watson, D., Christensen, L., Knudsen, K. et al. A dusty, normal galaxy in the epoch of reionization. Nature 519, 327–330 (2015).

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