Oxygen pumping II: Probing the Inhomogeneous Metal Enrichment at the Epoch of Reionization with High Frequency CMB Observations

TL;DR

This paper models the spectral distortion in the CMB caused by oxygen enrichment during reionization, exploring how metal bubbles around halos influence observable fluctuations and potential detection with future infrared detectors.

Contribution

It introduces a toy model for the spatial distribution of neutral oxygen and predicts the CMB spectral distortion fluctuations caused by metal enrichment during reionization.

Findings

Clustering signal of CMB distortion is weak but potentially detectable.

The power spectrum depends on wind velocity, halo mass, and epoch of enrichment.

Constraints on IGM metal enrichment history can be derived from future observations.

Abstract

At the epoch of reionization, when the high-redshift inter-galactic medium (IGM) is being enriched with metals, the 63.2 micron fine structure line of OI is pumped by the ~ 1300 AA soft UV background and introduces a spectral distortion in the Cosmic Microwave Background (CMB). Here we use a toy model for the spatial distribution of neutral oxygen, assuming metal bubbles surround dark matter halos, and compute the fluctuations of this distortion, and the angular power spectrum it imprints on the CMB. We discuss the dependence of the power spectrum on the velocity of the winds polluting the IGM with metals, the minimum mass of the halos producing these winds, and on the cosmic epoch when the OI pumping occurs. We find that, although the clustering signal of the CMB distortion is weak \delta y_{rms} ~ 10^{-7} (roughly corresponding to a temperature anisotropy of few nK), it may be reachable in deep integrations with high-sensitivity infrared detectors. Even without a detection, these instruments should be able to useful constraints on the heavy element enrichment history of the IGM.