Inverse-Compton scattering of the cosmic infrared background

Abstract

The thermal Sunyaev-Zel'dovich (tSZ) effect is the distortion generated in the cosmic microwave background (CMB) spectrum by the inverse-Compton scattering of CMB photons off free, energetic electrons, primarily located in the intracluster medium (ICM). Cosmic infrared background (CIB) photons from thermal dust emission in star-forming galaxies are expected to undergo the same process. In this work, we perform the first calculation of the resulting tSZ-like distortion in the CIB. Focusing on the CIB monopole, we use a halo model approach to calculate both the CIB signal and the Compton-y field that generates the distortion. We self-consistently account for the redshift co-evolution of the CIB and Compton-y fields: they are (partially) sourced by the same dark matter halos, which introduces new aspects to the calculation as compared to the CMB case. We find that the inverse-Compton distortion to the CIB monopole spectrum has a positive (negative) peak amplitude of ≈ 4 Jy/sr (≈ −5 Jy/sr) at 2260 GHz (940 GHz). In contrast to the usual tSZ effect, the distortion to the CIB spectrum has two null frequencies, at approximately 196 GHz and 1490 GHz. We perform a Fisher matrix calculation to forecast the detectability of this new distortion signal by future experiments. PIXIE would have sufficient instrumental sensitivity to detect the signal at 4σ, but foreground contamination reduces the projected signal-to-noise by a factor of ≈ 70. A future ESA Voyage 2050 spectrometer could detect the CIB distortion at ≈ 5σ significance, even after marginalizing over foregrounds. A measurement of this signal would provide new information on the star formation history of the Universe, and the distortion anisotropies may be accessible by near-future ground-based experiments.

class_sz I: Overview

“…We can compute auto-and cross-frequency power spectra at any frequency, as well as prediction for the CIB monopole. Ref [40] have used the CIB monopole implementation to predict the distortion caused by inverse Compton scattering of CIB photons against hot ICM electrons, see Ref. [40], although not accounting for intra-cluster scattering [41].…”

“…Ref [40] have used the CIB monopole implementation to predict the distortion caused by inverse Compton scattering of CIB photons against hot ICM electrons, see Ref. [40], although not accounting for intra-cluster scattering [41].…”