Forecasting ground-based sensitivity to the Rayleigh scattering of the CMB in the presence of astrophysical foregrounds

TL;DR

This paper forecasts the detectability of Rayleigh scattering in the CMB using upcoming ground-based experiments, accounting for instrumental, atmospheric, and astrophysical foreground effects, and assesses mitigation strategies.

Contribution

It introduces a comprehensive forecasting pipeline for Rayleigh scattering detection that includes realistic noise and foreground modeling for ground-based CMB experiments.

Findings

Detection significance ranges from 1.6 to 3.7 with upcoming experiments.

Atmospheric noise and CIB are primary limiting factors.

Combining with Planck data improves detection prospects.

Abstract

The Rayleigh scattering of cosmic microwave background (CMB) photons off the neutral hydrogen produced during recombination effectively creates an additional scattering surface after recombination that encodes new cosmological information, including the expansion and ionization history of the universe. A first detection of Rayleigh scattering is a tantalizing target for next-generation CMB experiments. We have developed a Rayleigh scattering forecasting pipeline that includes instrumental effects, atmospheric noise, and astrophysical foregrounds (e.g., Galactic dust, cosmic infrared background, or CIB, and the thermal Sunyaev-Zel'dovich effect). We forecast the Rayleigh scattering detection significance for several upcoming ground-based experiments, including SPT-3G+, Simons Observatory, CCAT-prime, and CMB-S4, and examine the limitations from atmospheric and astrophysical foregrounds as well as potential mitigation strategies. When combined with Planck data, we estimate that the ground-based experiments will detect Rayleigh scattering with a significance between 1.6 and 3.7, primarily limited by atmospheric noise and the CIB.