Open AccessA maximum likelihood analysis of the low cosmic microwave background multipoles from the Wilkinson Microwave Anisotropy Probe
Author(s) -
Efstathiou G.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07409.x
Subject(s) - cmb cold spot , physics , cosmic microwave background , astrophysics , amplitude , estimator , cosmology , cold dark matter , cosmic background radiation , dark matter , anisotropy , statistics , quantum mechanics , mathematics
The amplitudes of the quadrupole and octopole measured from the Wilkinson Microwave Anisotropy Probe ( WMAP ) appear to be lower than expected according to the concordance Λ cold dark matter (ΛCDM) cosmology. However, the pseudo‐ C ℓ estimator used by the WMAP team is non‐optimal. In this paper, we discuss the effects of Galactic cuts on pseudo‐ C ℓ and quadratic maximum likelihood estimators. An application of a quadratic maximum likelihood estimator to Galaxy‐subtracted maps produced by the WMAP team and Tegmark, de Oliveira‐Costa & Hamilton shows that the amplitudes of the low multipoles are stable to different Galactic cuts. In particular, the quadrupole and octopole amplitudes are found to lie in the ranges Δ T 2 2 = 176−250 (μK) 2 and Δ T 2 3 = 794−1183 (μK) 2 (and more likely to be at the upper ends of these ranges) rather than the values Δ T 2 2 = 123 (μK) 2 and Δ T 2 3 = 611 (μK) 2 found by the WMAP team. These results indicate that the discrepancy with the concordance ΛCDM model at low multipoles is not particularly significant and is in the region of a few per cent. This conclusion is consistent with an analysis of the low amplitude of the angular correlation function computed from quadratic maximum likelihood power spectrum estimates.