# Shot noise in the astrophysical gravitational-wave background

## TL;DR

This paper analyzes the shot noise affecting the anisotropies of the astrophysical gravitational-wave background, showing it dominates the true cosmological signal and outlining conditions for its recovery.

## Contribution

It derives an analytical expression for the shot noise bias in the gravitational-wave background anisotropies and assesses its impact on observing scenarios.

## Key findings

- Shot noise introduces a scale-invariant bias in the angular power spectrum.
- This bias generally dominates over the true cosmological signal.
- Long observation times and foreground removal are necessary to recover the true power spectrum.

## Abstract

We calculate the noise induced in the anisotropies of the astrophysical gravitational-wave background by finite sampling of both the galaxy distribution and the compact binary coalescence event rate. This shot noise leads to a scale-invariant bias term in the angular power spectrum $C_\ell$, for which we derive a simple analytical expression. We find that this bias dominates over the true cosmological power spectrum in any reasonable observing scenario, and that only with very long observing times and removal of a large number of foreground sources can the true power spectrum be recovered.