Academia Sinica Institute of Astronomy & Astrophysics
中央研究院天文及天文物理研究所
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Cosmology

Excessive shift of the CMB acoustic peaks of the Cold Spot area
Image Credit: Lung-Yih Chiang
Excessive shift of the CMB acoustic peaks of the Cold Spot area
Measurement of the acoustic peaks of the full-sky cosmic microwave background (CMB) temperature anisotropies has been instrumental in deciding the geometry and content of the universe, e.g. the first acoustic peak at ell~220 indicating a flat universe. However, acoustic peak positions vary in different parts of the sky due to statistical fluctuation. We test the statistics of the peak positions of small patches from ESA Planck data. By defining the "distance": how far the first 3 peaks positions are away from those in the best-fit LambdaCDM model, we found the patch (left) containing the mysterious "Cold Spot", an area near the Eridanus constellation where the temperature is significantly (p~0.01) lower than Gaussian theory predicts, displays large synchronous shift of peak positions towards smaller multipole numbers with significance lower than 1.11x10^{-4} ( right: the power spectrum of that patch from 4 different Planck CMB maps). The combination of large synchronous shifts in acoustic peaks and lower than usual temperature at the Cold Spot area results in a 4.73 sigma detection. We thus propose there is some extra localized unknown energy to stretch out the space in the transverse direction around the Cold Spot area to simultaneously account for the Cold Spot, excessive shift of the acoustic peaks, and the large under-dense regions.
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