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A possible cold imprint of voids on the microwave background radiation.

Cai, Yan-Chuan and Neyrinck, Mark and Szapudi, István and Cole, Shaun and Frenk, Carlos S. (2014) 'A possible cold imprint of voids on the microwave background radiation.', Astrophysical journal., 786 (2). p. 110.


We measure the average temperature decrement on the cosmic microwave background (CMB) produced by voids selected in the Sloan Digital Sky Survey Data Release 7 spectroscopic redshift galaxy catalog, spanning redshifts 0 < z < 0.44. We find an imprint amplitude between 2.6 and 2.9 μK as viewed through a compensated top-hat filter scaled to the radius of each void, we assess the statistical significance of the imprint at ~2σ, and we make crucial use of N-body simulations to calibrate our analysis. As expected, we find that large voids produce cold spots on the CMB through the integrated Sachs-Wolfe (ISW) effect. However, we also find that small voids in the halo density field produce hot spots, because they reside in contracting, larger-scale overdense regions. This is an important effect to consider when stacking CMB imprints from voids of different radii. We have found that the same filter radius that gives the largest ISW signal in simulations also yields close to the largest detected signal in the observations. However, although it is low in significance, our measured signal has a much higher amplitude than expected from ISW in the concordance ΛCDM universe. The discrepancy is also at the ~2σ level. We have demonstrated that our result is robust against the varying of thresholds over a wide range.

Item Type:Article
Keywords:Cosmic background radiation, Cosmology: observations, Large-scale structure of universe, Methods: statistical.
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Publisher statement:© 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
Date accepted:No date available
Date deposited:20 May 2014
Date of first online publication:May 2014
Date first made open access:No date available

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