Contribution of Radio Halos to the Foreground for SKA EoR Experiments
  The overwhelming foreground contamination is one of the primary impediments
to probing the Epoch of Reionization (EoR) through measuring the redshifted 21
cm signal. Among various foreground components, radio halos are less studied
and their impacts on the EoR observations are still poorly understood. In this
work, we employ the Press-Schechter formalism, merger-induced turbulent
re-acceleration model, and the latest SKA1-Low layout configuration to simulate
the SKA "observed" images of radio halos. We calculate the one-dimensional
power spectra from simulated images and find that radio halos can be about
$10^4$, $10^3$ and $10^{2.5}$ times more luminous than the EoR signal on scales
of $0.1\,\text{Mpc}^{-1} < k < 2\,\text{Mpc}^{-1}$ in the 120-128, 154-162, and
192-200 MHz bands, respectively. By examining the two-dimensional power spectra
inside properly defined EoR windows, we find that the power leaked by radio
halos can still be significant, as the power ratios of radio halos to the EoR
signal on scales of $0.5\,\text{Mpc}^{-1} \lesssim k \lesssim
1\,\text{Mpc}^{-1}$ can be up to about 230-800%, 18-95%, and 7-40% in the three
bands, when the 68% uncertainties caused by the variation of the number density
of bright radio halos are considered. Furthermore, we find that radio halos
located inside the far side-lobes of the station beam can also impose strong
contamination within the EoR window. In conclusion, we argue that radio halos
are severe foreground sources and need serious treatments in future EoR
experiments.
