Galaxy Counts on the Cosmic Microwave Background Cold Spot

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.