The Cold Spot on the Cosmic Microwave Background, Dr. Istvan Szapudi (IFA, University of Hawaii)

Thursday Nov 20, 2014, 3:15 PM → 4:45 PM Pacific/Honolulu

112 (Watanabe Hall)

The Cold Spot (CS) on the Cosmic Microwave Background (CMB) motivates searches for large voids that could produce a cold imprint via the Integrated Sachs-Wolfe Effect. We use the WISE-2MASS infrared galaxy catalog matched with Pan-STARRS1 (PS1) galaxies to search for such a supervoid in the direction of the CS. Our imaging catalog has median redshift z~0.14, and we obtain photometric redshifts from PS1 optical colours to create a tomographic map of the galaxy distribution. The radial profile centred on the CS shows a large low density region, extending over 10's of degrees. Motivated by previous CMB results, we test for underdensities within two angular radii, 5, and 15 degrees. The counts in photometric redshift bins show significantly low densities at high detection significance, ~5\sigma and ~6 \sigma, respectively, for the two fiducial radii. The line-of-sight position of the deepest region of the void is z~0.15-0.25. Our data, combined with an earlier measurement by Granett Etal (2010), are consistent with a large R= 220 \pm 50 hMpc supervoid with \delta= -0.14 \pm 0.04 centered at z=0.22\pm0.03. Such a supervoid, constituting at least a ~3.3\sigma fluctuation in a Gaussian distribution of the $\Lambda CDM$ model, is a plausible cause for the CS. (This talk is intended to be accessible in UH physicists in all subfields)

Slides CSTalkPS1Szapudi.pdf