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Lawrence Rudnick, Shea Brown, Liliya Williams

Contemplating Nothing. Lawrence Rudnick, Shea Brown, Liliya Williams. Radio galaxies. Large-scale structures. Dark Energy. Cosmic Microwave Background. Cosmic Microwave Background. W ilkinson. M icrowave A nisotropy P robe. Early Universe Inhomogeneities.

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Lawrence Rudnick, Shea Brown, Liliya Williams

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  1. Contemplating Nothing Lawrence Rudnick, Shea Brown, Liliya Williams

  2. Radio galaxies Large-scale structures Dark Energy Cosmic Microwave Background

  3. Cosmic Microwave Background Wilkinson Microwave Anisotropy Probe

  4. Early Universe Inhomogeneities

  5. Large-Scale Structure Formation

  6. Non-Gaussian Cold Spot • Non-Gaussian cold spot found in WMAP with SMHW • Many papers on possible origins for the cold spot: e.g. • Foreground subtraction errors • SZ effect • Intrinsic non-gaussianity • Integrated Sachs-Wolfe effect (ISW) by local voids ΔT~ -70 mK Vielva, P., Martinez-Gonzalez, E., Varreiro, R. B., Sanz, J. L., Cayon, L. 2004, ApJ 609, 22 Cruz, M., Martinez-Gonzalez, E., Vielva, P., Cayon, L. 2005, MNRAS 356, 29

  7. What we’ve learned... • CMB has tiny fluctuations from Early Universe, plus mysterious “cold spot”

  8. Large-Scale Structure Formation • Clumping of dark matter (and baryons) leads to stars and galaxies • Galaxies trace the dark matter distribution • Galaxies trace the potential wells

  9. Structures in the Universe

  10. NV N NVSS NRAO Very Large Array Sky Survey

  11. Hole in the NVSS • Area of the cold spot is also the “coldest spot” in the NVSS @ several resolutions • Spot is at the extreme end of the brightness distribution, but still part of the distribution

  12. Hole in the NVSS

  13. What we’ve learned... • CMB has tiny fluctuations from Early Universe, (at 46 billion light years away) plus mysterious “cold spot” • There is a “deficit” of radio galaxies in the same direction as the cold spot (6-10 billion light years away)

  14. What we’ve learned... • CMB has tiny fluctuations from Early Universe, (at 46 billion light years away) plus mysterious “cold spot” • There is a “deficit” of radio galaxies in the same direction as the cold spot (6-10 billion light years away)

  15. Effects of Dark Energy

  16. Simple Picture for the Cold spot Observed CMB at z=0 Mass distribution at z < 1 CMB NVSS survey – traces mass distribution WMAP- CMB anisotropies Late ISW causes correlation

  17. How Large of a Void is Needed? • We can do an order of magnitude calculation to find the size of the void need to create the “cold spot” • If we assume δ = -1 and z = 0.5-1.0, we calculate that a ~280 Mpc void is need. • Void statistics done so far find that the probability of finding a 280 Mpc void is ~5x10-10 • Second order effects could change the size of the void(s) needed Inoue & Silk 2006, 2007

  18. What we’ve learned... • CMB has tiny fluctuations from Early Universe, (at 46 billion light years away) plus mysterious “cold spot” • There is a “deficit” of radio galaxies in the same direction as the cold spot (6-10 billion light years away) • If the radio galaxy deficit is due to an empty void, 1 billion light years across, it could be responsible for the WMAP cold spot.

  19. Void Statistics • Although such a void seems very unlikely given the current void statistics, such large scales have not been investigated either in observations or simulations Average: δ = -0.94±0.02; R=(15.61±2.84) h-1 Mpc Hoyle & Vogeley 2004

  20. Radio galaxies Large-scale structures Dark Energy Cosmic Microwave Background

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