Exploring the origin of the fine structures in the CMB temperature angular power spectrum

Understand

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 $\ell=100 \sim 150$ reported by several authors.
• Using Monte-Carlo simulations, we confirm that the gap from the simple power law spectrum is a rare event, about 2.5--3$\sigma$, 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.