A new constraint on the $y$-distortion with FIRAS: implications for feedback models in galaxy formation and cosmic shear measurements

TL;DR

This paper presents a refined measurement of the cosmic microwave background's $y$-distortion using FIRAS data, constraining galaxy feedback models and impacting cosmic shear and SZ effect analyses.

Contribution

It improves the $y$-distortion measurement by a factor of three and rules out many baryonic feedback models in galaxy formation simulations.

Findings

Measured mean $y$-distortion $oxed{ ext{less than } 5.2 imes 10^{-6}}$ at 95\% C.L.

Rules out several baryonic feedback models in simulations.

Implications for cosmic shear and SZ effect data analysis.

Abstract

The $y$-type distortion of the blackbody spectrum of the cosmic microwave background radiation probes the pressure of the gas trapped in galaxy groups and clusters. We reanalyze archival data of the FIRAS instrument with an improved astrophysical foreground cleaning technique, and measure a mean $y$-distortion of $\langle y\rangle = (1.2\pm 2.0) \times 10^{-6}$ ($\langle y\rangle\lesssim 5.2\times 10^{-6}$ at 95\% C.L.), a factor of $\sim 3$ tighter than the original FIRAS results. This measurement directly rules out many models of baryonic feedback as implemented in cosmological hydrodynamical simulations, mostly using information in objects with mass $M\lesssim 10^{14} {\rm M}_{\odot}$. We discuss its implications for the analysis of cosmic shear and kinetic Sunyaev-Zel'dovich effect data, and future spectral distortion experiments.