Extragalactic Radio Sources and the WMAP Cold Spot

Apr, 2007
5 pages
Published in:
  • Astrophys.J. 671 (2007) 40-44
e-Print:

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Abstract: (arXiv)
We detect a dip of 20-30% in the surface brightness and number counts of NVSS sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of 1-10 degrees. We 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. Since the cold spot originates from structures at modest redshifts, there is no remaining need for non-Gaussian processes at the last scattering surface of the CMB. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, may thus be seen to operate on a single region for the first time. To create the magnitude and angular size of the WMAP cold spot requires a completely empty void of radius 140 Mpc at z<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.