Local Voids as the Origin of LargeAngle Cosmic Microwave Background Anomalies: The Effect of a Cosmological Constant
Abstract
We explore the large angular scale temperature anisotropies in the cosmic microwave background (CMB) due to homogeneous local dustfilled voids in a flat FriedmannRobertsonWalker universe with a cosmological constant. In comparison with the equivalent dustfilled void model in the Einsteinde Sitter background, we find that the anisotropy for compensated asymptotically expanding local voids can be larger, because secondorder effects enhance the linear integrated SachsWolfe (ISW) effect. However, for local voids that expand sufficiently faster than the asymptotic velocity of the wall, the secondorder effect can suppress the fluctuation due to the linear ISW effect. A pair of quasilinear compensated asymptotic local voids with radius (23)×10^{2} h^{1} Mpc and a matter density contrast δ_{m}~0.3 can be observed as cold spots with a temperature anisotropy ΔT/T~O(10^{5}) that might help explain the observed largeangle CMB anomalies. We predict that the associated anisotropy in the local Hubble constant in the direction of the voids could be as large as a few percent.
 Publication:

The Astrophysical Journal
 Pub Date:
 August 2007
 DOI:
 10.1086/517603
 arXiv:
 arXiv:astroph/0612347
 Bibcode:
 2007ApJ...664..650I
 Keywords:

 Cosmology: Cosmic Microwave Background;
 Cosmology: Miscellaneous;
 Cosmology: LargeScale Structure of Universe;
 Astrophysics
 EPrint:
 23 pages, 5 figures, version accepted for publication in ApJ with minor revision