Analysis of differential observations of the cosmological radio background : studying the SZE-21cm

TL;DR

This paper investigates the SZE-21cm effect as a probe of the early Universe, demonstrating its potential to detect the 21cm background through differential radio observations of galaxy clusters.

Contribution

It introduces a relativistic calculation of the SZE-21cm effect and demonstrates its recoverability via simulated differential observations using 21cmFAST.

Findings

Successful subtraction of foregrounds in simulated data

Recovery of the SZE-21cm signal through differential imaging

Validation of SZE-21cm as a probe for early Universe epochs

Abstract

In pursuit of understanding the early Universe and early processes occurring particularly in the Dark Ages (DA) and the Epoch of Reionization (EoR), it is vital that a suitable probe is identified. Probing these epochs will be useful in studies of the origin of first galaxies and most importantly formation of early black-holes. Over the past decade numerous probes have been proposed, with one of the most promising being the SZE-21cm, a specific form of the Sunyaev-Zeldovich effect (SZE) produced when photons of the 21cm background are inverse Compton up-scattered by electrons residing in hot plasma of cosmic structures such as galaxy clusters and active radio galaxies. The SZE-21cm is calculated in a full relativistic approach of the scattering processes of the CMB photons modified by the cosmological redshifted 21cm background in the hot intra-cluster medium of galaxy clusters capturing effects induced by relativistic corrections to this scattering and by multiple scattering effects. We apply image differencing techniques to simulated radio observations of galaxy clusters using the redshifted 21cm background, we conduct this making use of the public semi-numeric code 21cmFAST. We are able to achieve subtraction of contaminating foregrounds through pixel by pixel operations on the data retrieved from our simulated data cubes. We demonstrate that SZE-21cm can be recovered through differential observations of the 21cm background.