Extragalactic radio sources and the WMAP cold spot

Lawrence Rudnick, Shea Brown, Liliya R. Williams

Research output: Contribution to journalArticlepeer-review

113 Scopus citations


We detect a dip of 20%-45% in the surface brightness and number counts of NRAO VLA Sky Survey (NVSS) sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of ∼1° to 10°. Together with independent all-sky wavelet analyses, our results suggest that the dip in extragalactic brightness and number counts and the WMAP cold spot are physically related, i.e., that the coincidence is neither a statistical anomaly nor a WMAP foreground-correction problem. If the cold spot does originate from structures at modest redshifts, as we suggest, then there is no remaining need for non-Gaussian processes at the last scattering surface of the cosmic microwave background (CMB) to explain the cold spot. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, can now be seen to operate on a single region. To create the magnitude and angular size of the WMAP cold spot requires a ∼ 140 Mpc radius completely empty void atz < 1 along this line of sight. This is far outside the current expectations of the concordance cosmology, and adds to the anomalies seen in the CMB.

Original languageEnglish (US)
Pages (from-to)40-44
Number of pages5
JournalAstrophysical Journal
Issue number1
StatePublished - Dec 10 2007


  • Cosmic microwave background
  • Large-scale structure of universe
  • Radio continuum: galaxies

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