Exploring the origin of the fine structures in the CMB temperature angular power spectrum
Physical Review D
The angular power spectrum of the cosmic microwave background (CMB) temperature anisotropies is a good probe to look into the primordial density fluctuations at large scales in the universe. Here we re-examine the angular power spectrum of the Wilkinson Microwave Anisotropy Probe data, paying particular attention to the fine structures (oscillations) at ℓ=100 ∼ 150 reported by several authors. Using Monte-Carlo simulations, we confirm that the gap from the simple power law spectrum is a rare
... nt, about 2.5--3σ, if these fine structures are generated by experimental noise and the cosmic variance. Next, in order to investigate the origin of the structures, we examine frequency and direction dependencies of the fine structures by dividing the observed QUV frequency maps into four sky regions. We find that the structures around ℓ∼ 120 do not have significant dependences either on frequencies or directions. For the structure around ℓ∼ 140, however, we find that the characteristic signature found in the all sky power spectrum is attributed to the anomaly only in the South East region.