The dipole repeller


Our Local Group of galaxies is moving with respect to the cosmic microwave background (CMB) with a velocity1 of VCMB = 631 ± 20 km s−1 and participates in a bulk flow that extends out to distances of ~20,000 km s−1 or more24. There has been an implicit assumption that overabundances of galaxies induce the Local Group motion57. Yet underdense regions push as much as overdensities attract8, but they are deficient in light and consequently difficult to chart. It was suggested a decade ago that an underdensity in the northern hemisphere roughly 15,000 km s−1 away contributes significantly to the observed flow9. We show here that repulsion from an underdensity is important and that the dominant influences causing the observed flow are a single attractor — associated with the Shapley concentration — and a single previously unidentified repeller, which contribute roughly equally to the CMB dipole. The bulk flow is closely anti-aligned with the repeller out to 16,000 ± 4,500 km s−1. This ‘dipole repeller’ is predicted to be associated with a void in the distribution of galaxies.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: A face-on view of a slice 6,000kms−1 thick, normal to the direction of the pointing vector r ˆ = ( 0.604,0.720 , 0.342 ) .
Figure 2: A 3D view of the velocity field.
Figure 3: Aitoff projection in galactic coordinates of the principal structures and directions that characterize the flow.


  1. 1

    Fixsen, D. J. et al. The spectrum cosmic microwave background from the full COBE FIRAS data set. Astrophys. J. 473, 576–587 (1996).

    Article  ADS  Google Scholar 

  2. 2

    Nusser, A. & Davis, M. The cosmological bulk flow: Consistency with ΛCDM and z ≈ 0 constraints on σ 8 and γ . Astrophys. J. 736, 93 (2011).

    Article  ADS  Google Scholar 

  3. 3

    Watkins, R. & Feldman, H. A. Large-scale bulk flows from the Cosmicflows-2 catalogue. Mon. Not. R. Astron. Soc. 447, 132–139 (2015).

    Article  ADS  Google Scholar 

  4. 4

    Hoffman, Y., Courtois, H. M. & Tully, R. B. Cosmic bulk flow and the local motion from Cosmicflows-2. Mon. Not. R. Astron. Soc. 449, 4494–4505 (2015).

    Article  ADS  Google Scholar 

  5. 5

    Lilje, P. B., Yahil, A. & Jones, B. J. T. The tidal velocity field in the Local Supercluster. Astrophys. J. 307, 91–96 (1986).

    Article  ADS  Google Scholar 

  6. 6

    Lynden-Bell, D. et al. Spectroscopy and photometry of elliptical galaxies. V: Galaxy streaming toward the new supergalactic center. Astrophys. J. 326, 19–49 (1988).

    Article  ADS  Google Scholar 

  7. 7

    Dressler, A. The Great Attractor: Do galaxies trace the large-scale mass distribution? Nature 350, 391–397 (1991).

    Article  ADS  Google Scholar 

  8. 8

    Lahav, O., Lynden-Bell, D. & Rowan-Robinson, M. The peculiar acceleration of the Local Group as deduced from the optical and IRAS flux dipoles. Mon. Not. R. Astron. Soc. 234, 677–701 (1988).

    Article  ADS  Google Scholar 

  9. 9

    Kocevski, D. D. & Ebeling, H. On the origin of the Local Group peculiar velocity. Astrophys. J. 645, 1043–1053 (2006).

    Article  ADS  Google Scholar 

  10. 10

    Dekel, A., Bertschinger, E. & Faber, S. M. Potential, velocity, and density fields from sparse and noisy redshift–distance samples: Method. Astrophys. J. 364, 349–369 (1990).

    Article  ADS  Google Scholar 

  11. 11

    Zaroubi, S., Hoffman, Y. & Dekel, A. Wiener reconstruction of large-scale structure from peculiar velocities. Astrophys. J. 520, 413–425 (1999).

    Article  ADS  Google Scholar 

  12. 12

    Courtois, H. M., Hoffman, Y., Tully, R. B. & Gottloeber, S. Three-dimensional velocity and density reconstructions of the local Universe with Cosmicflows-1. Astrophys. J. 744, 43 (2012).

    Article  ADS  Google Scholar 

  13. 13

    Courtois, H. M., Pomarède, D., Tully, R. B., Hoffman, Y. & Courtois, D. Cosmography of the local Universe. Astron. J. 146, 69 (2013).

    Article  ADS  Google Scholar 

  14. 14

    Tully, R.B., Courtois, H., Hoffman, Y. & Pomarède, D .The Laniakea supercluster of galaxies. Nature 513, 71–73 (2014).

    Article  ADS  Google Scholar 

  15. 15

    Pomarède, D., Tully, R. B., Hoffman, Y. & Courtois, H. M. The Arrowhead mini-supercluster of galaxies. Astrophys. J. 812, 17 (2015).

    Article  ADS  Google Scholar 

  16. 16

    Tully, R. B. et al. Cosmicflows-2: The data. Astron. J. 146, 86 (2013).

    Article  ADS  Google Scholar 

  17. 17

    Hoffman, Y. et al. A kinematic classification of the cosmic web. Mon. Not. R. Astron. Soc. 425, 2049–2057 (2012).

    Article  ADS  Google Scholar 

  18. 18

    Jaffe, A. H. & Kaiser, N. Likelihood analysis of large-scale flows. Astrophys. J. 455, 26 (1995).

    Article  ADS  Google Scholar 

  19. 19

    Hoffman, Y., Eldar, A., Zaroubi, S. & Dekel, A. The large-scale tidal velocity field. Preprint at (2001).

  20. 20

    Feldman, H. A., Watkins, R. & Hudson, M. J. Cosmic flows on 100 h−1 Mpc scales: standardized minimum variance bulk flow, shear and octupole moments. Mon. Not. R. Astron. Soc. 407, 2328–2338 (2010).

    Article  ADS  Google Scholar 

  21. 21

    Scaramella, R., Baiesi-Pillastrini, G., Chincarini, G., Vettolani, G. & Zamorani, G. A marked concentration of galaxy clusters - Is this the origin of large-scale motions? Nature 338, 562–564 (1989).

    Article  ADS  Google Scholar 

  22. 22

    Raychaudhury, S. The distribution of galaxies in the direction of the ‘Great Attractor’. Nature 342, 251–255 (1989).

    Article  ADS  Google Scholar 

  23. 23

    Peebles, P. J. E. The Large-Scale Structure of the Universe (Princeton Univ. Press, 1980).

    Google Scholar 

  24. 24

    Hoffman, Y. & Ribak, E. Constrained realizations of Gaussian fields: A simple algorithm. Astrophys. J. 380, L5–L8 (1991).

    Article  ADS  Google Scholar 

  25. 25

    Hoffman, Y. in Data Analysis in Cosmology Lecture Notes in Physics Vol. 665 (ed. Martínez, V. J., Saar, E., Martínez-González, E. & Pons-Bordería, M.-J. ) 565–583 (Springer, 2009).

    Google Scholar 

  26. 26

    Zaroubi, S., Hoffman, Y., Fisher, K. B. & Lahav, O. Wiener reconstruction of the large-scale structure. Astrophys. J. 449, 446–459 (1995).

    Article  ADS  Google Scholar 

Download references


We thank J. Sorce and S. Gottloeber for discussions and A. Dupuy for her help in preparing Fig. 3. We thank K. Bowles and S. Thompson for the narration in the Supplementary Video. Support has been provided by the Israel Science Foundation (1013/12), the Institut Universitaire de France, the US National Science Foundation, Space Telescope Science Institute for observations with Hubble Space Telescope, the Jet Propulsion Lab for observations with Spitzer Space Telescope and NASA for analysis of data from the Wide-field Infrared Survey Explorer.

Author information




R.B.T. and H.M.C. carried out the observations and data analysis; D.P. contributed graphics and visualization; Y.H. carried out the numerical and theoretical analysis. All co-authors contributed to the writing of the paper, led by Y.H.

Corresponding author

Correspondence to Yehuda Hoffman.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Figures 1–3, Supplementary Table 1. (PDF 1220 kb)

Supplementary Video

The dipole repeller. (MP4 83651 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Hoffman, Y., Pomarède, D., Tully, R. et al. The dipole repeller. Nat Astron 1, 0036 (2017).

Download citation

Further reading