Dust-free quasars in the early Universe

Abstract

The most distant quasars known, at redshifts z ≈ 6, generally have properties indistinguishable from those of lower-redshift quasars in the rest-frame ultraviolet/optical and X-ray bands1,2,3. This puzzling result suggests that these distant quasars are evolved objects even though the Universe was only seven per cent of its current age at these redshifts. Recently one z ≈ 6 quasar was shown not to have any detectable emission from hot dust4, but it was unclear whether that indicated different hot-dust properties at high redshift or if it is simply an outlier. Here we report the discovery of a second quasar without hot-dust emission in a sample of 21 z ≈ 6 quasars. Such apparently hot-dust-free quasars have no counterparts at low redshift. Moreover, we demonstrate that the hot-dust abundance in the 21 quasars builds up in tandem with the growth of the central black hole, whereas at low redshift it is almost independent of the black hole mass. Thus z ≈ 6 quasars are indeed at an early evolutionary stage, with rapid mass accretion and dust formation. The two hot-dust-free quasars are likely to be first-generation quasars born in dust-free environments and are too young to have formed a detectable amount of hot dust around them.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Spitzer SEDs of z  ≈ 6 quasars.
Figure 2: Luminosity and redshift dependence of the hot-dust abundance for type 1 quasars.
Figure 3: Correlation between the hot-dust abundance and black hole mass for type 1 quasars.

References

  1. 1

    Fan, X. et al. A survey of z > 5.7 quasars in the Sloan Digital Sky Survey. III. Discovery of five additional quasars. Astron. J. 128, 515–522 (2004)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Jiang, L. et al. Gemini near-infrared spectroscopy of luminous z 6 quasars: chemical abundances, black hole masses, and Mg II absorption. Astron. J. 134, 1150–1161 (2007)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Shemmer, O. et al. Chandra observations of the highest redshift quasars from the Sloan Digital Sky Survey. Astrophys. J. 644, 86–99 (2006)

    ADS  Article  Google Scholar 

  4. 4

    Jiang, L. et al. Probing the evolution of infrared properties of z 6 quasars: Spitzer observations. Astron. J. 132, 2127–2134 (2006)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Fan, X. et al. Constraining the evolution of the ionizing background and the epoch of reionization with z 6 quasars. II. A sample of 19 quasars. Astron. J. 132, 117–136 (2006)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Willott, C. J. et al. Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey. Astron. J. 134, 2435–2450 (2007)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Kurk, J. D. et al. Black hole masses and enrichment of z 6 SDSS quasars. Astrophys. J. 669, 32–44 (2007)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Antonucci, R. Unified models for active galactic nuclei and quasars. Annu. Rev. Astron. Astrophys. 31, 473–521 (2003)

    ADS  Article  Google Scholar 

  9. 9

    Elitzur, M. The toroidal obscuration of active galactic nuclei. N. Astron. Rev. 52, 274–288 (2008)

    ADS  Article  Google Scholar 

  10. 10

    Rieke, G. H. The infrared emission of Seyfert galaxies. Astrophys. J. 226, 550–558 (1978)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Hyland, A. R. & Allen, D. A. An infrared study of quasars. Mon. Not. R. Astron. Soc. 199, 943–952 (1982)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Haas, M. et al. The ISO view of Palomar-Green quasars. Astron. Astrophys. 402, 87–111 (2003)

    ADS  Article  Google Scholar 

  13. 13

    Richards, G. T. et al. Spectral energy distributions and multiwavelength selection of type 1 quasars. Astrophys. J. 166 (Suppl.). 470–497 (2006)

    CAS  Article  Google Scholar 

  14. 14

    Glikman, E., Helfand, D. J. & White, R. L. A near-infrared spectral template for quasars. Astrophys. J. 640, 579–591 (2006)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Kurk, J. D. et al. Near-infrared spectroscopy of SDSS J0303–0019: a low-luminosity, high-Eddington-ratio quasar at z 6. Astrophys. J. 702, 833–837 (2009)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Ryan, C. J., De Robertis, M. M., Virani, S., Laor, A. & Dawson, P. C. The central engines of narrow-line Seyfert 1 galaxies. Astrophys. J. 654, 799–813 (2007)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Wang, R. et al. Millimeter and radio observations of z 6 quasars. Astron. J. 134, 617–627 (2007)

    ADS  Article  Google Scholar 

  18. 18

    Wang, R. et al. Thermal emission from warm dust in the most distant quasars. Astrophys. J. 687, 848–858 (2008)

    ADS  CAS  Article  Google Scholar 

  19. 19

    Hines, D. C. et al. Spitzer observations of high-redshift QSOs. Astrophys. J. 641, 85–88 (2006)

    ADS  Article  Google Scholar 

  20. 20

    Neugebauer, G. et al. Continuum energy distributions of quasars in the Palomar-Green Survey. Astrophys. J. 63 (Suppl.). 615–644 (1987)

    CAS  Article  Google Scholar 

  21. 21

    Haas, M. et al. Dust in PG quasars as seen by ISO. Astron. Astrophys. 354, 453–466 (2000)

    ADS  CAS  Google Scholar 

  22. 22

    Hernán-Caballero, A. et al. Mid-infrared spectroscopy of infrared-luminous galaxies at z 0.5–3. Mon. Not. R. Astron. Soc. 395, 1695–1722 (2009)

    ADS  Article  Google Scholar 

  23. 23

    Vestergaard, M. & Peterson, B. M. Determining central black hole masses in distant active galaxies and quasars. II. Improved optical and UV scaling relationships. Astrophys. J. 641, 689–709 (2006)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Elvis, M., Marengo, M. & Karovska, M. Smoking quasars: a new source for cosmic dust. Astrophys. J. 567, 107–110 (2002)

    ADS  Article  Google Scholar 

  25. 25

    Maiolino, R. et al. A supernova origin for dust in a high-redshift quasar. Nature 431, 533–535 (2004)

    ADS  CAS  Article  Google Scholar 

  26. 26

    Stratta, G., Maiolino, R., Fiore, F. & D’Elia, V. Dust properties at z = 6.3 in the host galaxy of GRB 050904. Astrophys. J. 661, 9–12 (2007)

    ADS  Article  Google Scholar 

  27. 27

    Shen, Y., Greene, J. E., Strauss, M. A., Richards, G. T. & Schneider, D. P. Biases in virial black hole masses: an SDSS perspective. Astrophys. J. 680, 169–190 (2008)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Barth, A. J., Martini, P., Nelson, C. H. & Ho, L. C. Iron emission in the z = 6.4 quasar SDSS J114816.64+525150.3. Astrophys. J. 594, 95–98 (2003)

    ADS  Article  Google Scholar 

  29. 29

    Vestergaard, M. & Osmer, P. S. Mass functions of the active black holes in distant quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the color-selected sample of the SDSS fall equatorial stripe. Astrophys. J. 699, 800–816 (2009)

    ADS  CAS  Article  Google Scholar 

  30. 30

    Lavalley, M., Isobe, T. & Feigelson, E. in Astronomical Data Analysis Software and Systems I (eds Worrall, D. M., Biemesderfer, C. & Barnes, J.) 245–247 (ASP Conf. Ser. Vol. 25, Astronomical Society of the Pacific, 1992)

    Google Scholar 

Download references

Acknowledgements

This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. X.F. acknowledges support by NSF AST, a Packard Fellowship for Science and Engineering, and a John Simon Guggenheim Memorial Fellowship. W.N.B. was supported by the NASA ADP program. C.L.C. thanks the Max-Planck-Gesellschaft and the Humboldt-Stiftung for support through the Max-Planck-Forschungspreis. J.D.K. thanks the DFG for support via German-Israeli Project Cooperation. The Dark Cosmology Centre is funded by the Danish National Research Foundation.

Author Contributions L.J. and X.F. designed the project, reduced and analysed the data, and prepared the manuscript; W.N.B., M.A.S. and F.W. performed statistics and edited the manuscript; C.L.C., E.E., D.C.H. and G.T.R. prepared observations; J.D.K. analysed NIR spectra of two hot-dust-free quasars; Y.S. and M.V. measured black hole masses. All authors helped with the scientific interpretations and commented on the manuscript.

Author information

Affiliations

Authors

Corresponding author

Correspondence to Linhua Jiang.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Jiang, L., Fan, X., Brandt, W. et al. Dust-free quasars in the early Universe. Nature 464, 380–383 (2010). https://doi.org/10.1038/nature08877

Download citation

Further reading

Comments

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.

Search

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