The cold spot as a large void: lensing effect on CMB two and three point correlation functions
- Dipartimento di Fisica dell'Università degli Studi di Ferrara and INFN sezione di Ferrara, Via Saragat 1, I-44100 Ferrara (Italy)
- CERN, Theory Division, CH-1211 Geneva 23 (Switzerland)
The ''Cold Spot'' in the CMB sky could be due to the presence of an anomalous huge spherical underdense region — a ''Void'' — of a few hundreds Mpc/h radius. Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low l, but also at high l through Lensing, which is a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data only if the Void radius is at least L ∼> 1 Gpc/h, while it will be visible by the Planck satellite if L ∼> 800 Mpc/h. We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky. Moreover, there should be non-zero correlations in the non-diagonal two-point function. For the bispectrum, the effect becomes important for squeezed triangles with two very high l's: this signal can be detected by Planck if the Void radius is at least L ∼> 400 Mpc/h, while higher resolution experiments should be able to probe the entire parameter space. We have also estimated the contamination of the primordial non-Gaussianity f{sub NL} due to this signal, which turns out to be negligible.
- OSTI ID:
- 22273201
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 07 Vol. 2009; ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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