Revisiting secondary CMB distortions due to kinetic Sunyaev–Zel’dovich effect from quasar bubbles before reionization

ABSTRACT We discuss the secondary cosmic microwave background (CMB) anisotropy due to kinetic Sunyaev–Zel’dovich (kSZ) effect from ionized bubbles around individual quasars prior to the reionization of the Universe. The bubbles create local ionization modulations which move with the large-scale structure linear bulk flow and act as sources for kSZ. We improve upon previous calculations of this effect, using a halo model based description of quasar abundance, and find that the kSZ distortion power spectrum, Cℓ, from the bubbles to be sub-dominant to kSZ from patchy reionization driven by galaxies. However, the shape of the two Cℓ’s are very different with the quasar bubble Cℓ having a peak at ℓ ≈ 500–700 whereas the Cℓ due to patchy reionization flattening out at ℓ > 1000 thus making it plausible to separate the two using Cℓ template-fitting in a future survey like CMB-HD. Next, we look at the imprint of a single quasar bubble on the CMB and show that it can be detected in a high-resolution, ambitious effort like CMB-HD. A detection of a high redshift quasar bubble in the CMB would carry complimentary information to its detection in H i or Lyman-α and a joint analysis can be used to break parameter degeneracies.