# Modelling the WMAP large-angle anomalies as an effect of a local density inhomogeneity - Astrophysics > Cosmology and Nongalactic Astrophysics

Modelling the WMAP large-angle anomalies as an effect of a local density inhomogeneity - Astrophysics > Cosmology and Nongalactic Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We investigate large-angle scale temperature anisotropy in the CosmicMicrowave Background CMB with the Wilkinson Microwave Anisotropy Probe WMAPdata and model the large-angle anomalies as the effect of the CMB quadrupoleanisotropies caused by the local density inhomogeneities. The quadrupole causedby the local density inhomogeneities is different from the special relativitykinematic quadrupole. If the observer inhabits a strong inhomogeneous region,the local quadrupole should not be neglected. We calculate such localquadrupole under the assumption that there is a huge density fluctuation fieldin direction $284^{\circ},74^{\circ}$, where the density fluctuation is$10^{-3}$, and its center is $\sim 112h^{-1} m {Mpc}$ away from us. Afterremoving such mock signals from WMAP data, the power in quadrupole, $C 2$,increases from the range $200\sim260\mu m{K^2}$ to $\sim1000\mu m{K^2}$.The quantity S, which is used to estimate the alignment between the quadrupoleand the octopole, decreases from $0.7\sim0.74$ to $0.31\sim0.37$, while themodel predict that $C 2=1071.5\mu m{K^2}$, $S=0.412$. So our local densityinhomogeneity model can, in part, explain the WMAP low-$\ell$ anomalies.

Author: ** Li-Ping He, Quan Guo**

Source: https://arxiv.org/