CMB Isotropy Anomalies and the Local Kinetic Sunyaev-Zel'dovich Effect

Abstract

Several anomalies have been identified which may imply a breakdown of the statistical isotropy of the cosmic microwave background (CMB). In particular, an anomalous alignment of the quadrupole and octopole and a hemispherical power asymmetry have increased in significance as the data have improved. There have been several attempts to explain these observations which explore isotropy breaking mechanisms within the early universe, but little attention has been given to the possibility that these anomalies have their origin within the local universe. We explore such a mechanism by considering the kinetic Sunyaev-Zel'dovich effect due to a gaseous halo associated with the Milky Way. Considering several physical models of an anisotropic free electron optical depth contributed by such a halo, we find that the associated screening maps of the primordial anisotropies have the necessary orientations to affect the anomaly statistics very significantly, but only if the column density of free electrons in the halo is at least an order of magnitude higher than indicated by current observations.

10 pages, 4 figures

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• Is the CMB asymmetry due to the kinematic dipole?
• Large scale directional anomalies in the WMAP 5yr ILC map
• Some statistical remarks on the Giant GRB Ring
• On Preferred Axes in WMAP Cosmic Microwave Background Data after Subtraction of the Integrated Sachs-Wolfe Effect
• Cosmological Implications of the CMB Large-scale Structure
• Constraints on the SZ Power Spectrum on Degree Angular Scales in WMAP Data
• The kinetic Sunyaev-Zel'dovich effect from the diffuse gas in the Local Group
• Reconstruction of Missing Data using Iterative Harmonic Expansion