Foreground Subtraction in Intensity Mapping with the SKA
  21cm intensity mapping experiments aim to observe the diffuse neutral
hydrogen (HI) distribution on large scales which traces the Cosmic structure.
The Square Kilometre Array (SKA) will have the capacity to measure the 21cm
signal over a large fraction of the sky. However, the redshifted 21cm signal in
the respective frequencies is faint compared to the Galactic foregrounds
produced by synchrotron and free-free electron emission. In this article, we
review selected foreground subtraction methods suggested to effectively
separate the 21cm signal from the foregrounds with intensity mapping
simulations or data. We simulate an intensity mapping experiment feasible with
SKA phase 1 including extragalactic and Galactic foregrounds. We give an
example of the residuals of the foreground subtraction with a independent
component analysis and show that the angular power spectrum is recovered within
the statistical errors on most scales. Additionally, the scale of the Baryon
Acoustic Oscillations is shown to be unaffected by foreground subtraction.
