Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

A velocity dipole in the distribution of radio galaxies

Nature volume 416, pages 150–152 (2002)Cite this article

Abstract

The motion of our Galaxy through the Universe is reflected in a systematic shift in the temperature of the cosmic microwave background1—because of the Doppler effect, the temperature of the background is about 0.1 per cent higher in the direction of motion, with a correspondingly lower temperature in the opposite direction. This effect is known as dipole anisotropy. If our standard cosmological model is correct, a related dipole effect should also be present as an enhancement in the surface density of distant galaxies in the direction of motion2. The main obstacle to finding this signal is the uneven distribution of galaxies in the local supercluster, which drowns out the small cosmological signal. Here we report a detection of the expected cosmological dipole anisotropy in the distribution of galaxies. We use a survey of radio galaxies that are mainly located at cosmological distances, so the contamination from nearby clusters is small. When local radio galaxies are removed from the sample, the resulting dipole is in the same direction as the temperature anisotropy of the microwave background, and close to the expected amplitude. The result therefore confirms the standard cosmological interpretation of the microwave background.

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

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

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

Figure 1: The NVSS suffers from systematic fluctuations in source surface density across the sky at low flux densities.
Figure 2: Our measured dipole direction agrees with that of the CMB dipole.
Figure 3: The clustering dipole originates from redshifts z < 0.03.
Figure 4: The PSCz and RCBG3 catalogues include almost all nearby NVSS galaxies.

Similar content being viewed by others

References

  1. Smoot, G., Gorenstein, M. & Muller, R. Detection of anisotropy in the cosmic black-body radiation. Phys. Rev. Lett. 39, 898–901 (1977).

    Article  ADS  Google Scholar 

  2. Ellis, G. & Baldwin, J. On the expected anisotropy of radio source counts. Mon. Not. R. Astron. Soc. 206, 377–381 (1984).

    Article  ADS  Google Scholar 

  3. Scharf, C. et al. The 2–10 keV X-ray background dipole and its cosmological implications. Astrophys. J. 544, 49–62 (2000).

    Article  ADS  CAS  Google Scholar 

  4. Baleisis, A., Lahav, O., Loan, A. J. & Wall, J. V. Searching for large-scale structure in deep radio surveys. Mon. Not. R. Astron. Soc. 297, 545–558 (1998).

    Article  ADS  Google Scholar 

  5. Lahav, O. Optical dipole anisotropy. Mon. Not. R. Astron. Soc. 225, 213–220 (1987).

    Article  ADS  CAS  Google Scholar 

  6. Rowan-Robinson, M. et al. The IRAS PSCz dipole. Mon. Not. R. Astron. Soc. 314, 375–397 (2000).

    Article  ADS  Google Scholar 

  7. Condon, J. J. The NRAO VLA Sky Survey. Astron. J. 115, 1693–1716 (1998).

    Article  ADS  Google Scholar 

  8. Dunlop, J. S. & Peacock, J. A. The redshift cut-off in the luminosity function of radio galaxies and quasars. Mon. Not. R. Astron. Soc. 247, 19–42 (1990).

    ADS  Google Scholar 

  9. Saunders, W. et al. The PSCz catalogue. Mon. Not. R. Astron. Soc. 317, 55–64 (2000).

    Article  ADS  Google Scholar 

  10. Corwin, H., Buta, R. & de Vacouleurs, G. Corrections and additions to the third reference catalogue of bright galaxies. Astron. J. 108, 2128–2144 (1994).

    Article  ADS  Google Scholar 

  11. Lineweaver, C. in Proc. XVIth Moriond Astrophysics Meeting 69–75 (Editions Frontieres, Gif-sur-Yvette, 1997).

    Google Scholar 

Download references

Acknowledgements

We thank L. Miller and S. Rawlings for comments on early drafts. We also thank J. Condon for comments and suggestions.

Author information

Authors and Affiliations

  1. Astrophysics, Nuclear and Astrophysics Laboratory, University of Oxford, Keble Road, Oxford, OX1 3RH, UK

    Chris Blake & Jasper Wall

Authors
  1. Chris Blake
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jasper Wall
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Chris Blake.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Blake, C., Wall, J. A velocity dipole in the distribution of radio galaxies. Nature 416, 150–152 (2002). https://doi.org/10.1038/416150a

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/416150a

This article is cited by

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

Advanced search

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