The cold spot on the cosmic microwave background (CMB) could arise due to a supervoid at low redshift through the integrated Sachs-Wolfe effect. We imaged the region with MegaCam on the Canada-France-Hawaii Telescope and present galaxy counts in photometric redshift bins. We rule out the existence of a 100 Mpc radius spherical supervoid with underdensity δ = -0.3 at 0.5 < z < 0.9 at high significance. The data are consistent with an underdensity at low redshift, but the fluctuations are within the range of cosmic variance and the low-density areas are not contiguous on the sky. Thus, we find no strong evidence for a supervoid. We cannot resolve voids smaller than a 50 Mpc radius; however, these can only make a minor contribution to the CMB temperature decrement.
The Astrophysical Journal
- Pub Date:
- May 2010
- cosmic background radiation;
- cosmology: observations;
- large-scale structure of universe;
- methods: statistical;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- 9 pages. Minor updates to match the article accepted to ApJ.