Signatures of high-redshift galactic outflows in the thermal Sunyaev Zel'dovich effect

TL;DR

This paper presents an analytic model showing that high-redshift galactic outflows significantly contribute to the thermal Sunyaev Zel'dovich effect anisotropies, which upcoming CMB experiments could detect to study early galaxy feedback.

Contribution

The authors develop a simple analytic framework to quantify the SZ anisotropies caused by SNe-driven outflows at z>6, highlighting their dominance over other heating sources.

Findings

Galactic outflows are likely the main source of high-z thermal energy injection.

Next-generation CMB experiments can detect these outflows through cross-correlation with galaxy surveys.

Thermal SZ anisotropies can probe supernova feedback in early galaxies.

Abstract

Anisotropies of the Sunyaev Zel'dovich (SZ) effect serve as a powerful probe of the thermal history of the universe. At high redshift, hot galactic outflows driven by supernovae (SNe) can inject a significant amount of thermal energy into the intergalactic medium, causing a strong $y$-type distortion of the CMB spectrum through inverse Compton scattering. The resulting anisotropies of the $y$-type distortion are sensitive to key physical properties of high-$z$ galaxies pertaining to the launch of energetic SNe-driven outflows, such as the efficiency and the spatio-temporal clustering of star formation. We develop a simple analytic framework to calculate anisotropies of $y$-type distortion associated with SNe-powered outflows of galaxies at $z>6$. We show that galactic outflows are likely the dominant source of thermal energy injection, compared to contributions from reionized bubbles and gravitational heating. We further show that next-generation CMB experiments such as LiteBIRD are likely to detect the contribution to $y$ anisotropies from high-$z$ galactic outflows through the cross-correlation with surveys of Lyman-break galaxies by e.g. the Roman Space Telescope. Our analysis and forecasts demonstrate that thermal SZ anisotropies can be a promising probe of SN feedback and outflows in early star-forming galaxies.