Foreground simulations for the LOFAR - Epoch of Reionization Experiment

TL;DR

This paper presents simulations of astrophysical foregrounds for the LOFAR Epoch of Reionization experiment, demonstrating that polynomial fitting can effectively reconstruct the cosmological 21-cm signal amidst foreground contamination.

Contribution

It introduces simulated foreground datacubes tailored for LOFAR EoR observations and evaluates the effectiveness of polynomial fitting in signal recovery under realistic noise and instrument conditions.

Findings

Polynomial fitting recovers the 21-cm signal with ~52 mK noise levels.

Foreground simulations include polarized galactic synchrotron maps with Faraday effects.

Simple polynomial models are effective under idealized instrument response assumptions.

Abstract

Future high redshift 21-cm experiments will suffer from a high degree of contamination, due both to astrophysical foregrounds and to non-astrophysical and instrumental effects. In order to reliably extract the cosmological signal from the observed data, it is essential to understand very well all data components and their influence on the extracted signal. Here we present simulated astrophysical foregrounds datacubes and discuss their possible statistical effects on the data. The foreground maps are produced assuming 5 deg x 5 deg windows that match those expected to be observed by the LOFAR Epoch-of-Reionization (EoR) key science project. We show that with the expected LOFAR-EoR sky and receiver noise levels, which amount to ~52 mK at 150 MHz after 300 hours of total observing time, a simple polynomial fit allows a statistical reconstruction of the signal. We also show that the polynomial fitting will work for maps with realistic yet idealised instrument response, i.e., a response that includes only a uniform uv coverage as a function of frequency and ignores many other uncertainties. Polarized galactic synchrotron maps that include internal polarization and a number of Faraday screens along the line of sight are also simulated. The importance of these stems from the fact that the LOFAR instrument, in common with all current interferometric EoR experiments has an instrumentally polarized response.