# Sunyaev-Zel'dovich anisotropy due to Primordial black holes

## TL;DR

This paper models the Sunyaev-Zel'dovich effect caused by primordial black holes, showing it can produce a flat small-scale CMB anisotropy that may dominate primordial fluctuations and inform PBH abundance constraints.

## Contribution

It introduces a new model for the SZ effect from PBHs and predicts its impact on small-scale CMB anisotropies, linking PBH properties to observable signals.

## Key findings

- SZ anisotropy has a flat spectrum on small scales (l ≤ 2000)
- PBH-induced SZ effect can dominate primordial fluctuations on small scales
- Small-scale CMB measurements can constrain PBH abundance

## Abstract

We investigate the Sunyaev-Zel'dovich (SZ) effect caused by primordial black holes (PBHs) on the cosmic microwave background (CMB) temperature fluctuations. The gas accreting on a PBH heats up by the release of the gravitational energy. As a result, the heated gas in the vicinity of the PBH emits the UV and X-ray photons. These photons can ionize and heat the intergalactic medium (IGM) around the PBH. Assuming the simple model of these emitting photons, we compute the profiles of the IGM ionization fraction and temperature around a PBH. Using these profiles, we evaluate the Compton $y$-parameter created by the IGM gas around a PBH. Finally, we estimate the CMB temperature angular power spectrum due to the PBH SZ effect in our model. We show that the SZ temperature anisotropy due to the PBHs has the flat angular power spectrum on small scale, $l\leq2000$ and could dominate the primordial temperature spectrum on smaller scales than the Silk scale. This flat spectrum extends to the scale of the ionized region by the PBH emission. We also discuss the impact of the small-scale CMB measurement on the PBH abundance based on our results.