Polarization leakage in epoch of reionization windows: The Low Frequency Array Case

The farther we look in space, the earlier we see in time. By observing a radio signal of 21cm wavelength coming from the epoch of reionization, when the universe was less than a billion years old, we can understand how the first stars, galaxies and black holes formed. This signal has not been detected yet and LOFAR, centered near Exloo, is one of the main telescopes trying to detect it. To discover this signal, we have to remove all foregrounds, the radiation coming from the intervening medium. One of the most difficult foregrounds is the diffuse emission from our Galaxy. In this thesis we have quantified the effect of the polarized component of this diffuse emission on the detection of the 21cm signal. The polarized component can get mixed with the desired signal because of the errors of the observing instrument. Using different models of the instrumental errors and observations of the polarized emission at low frequency, we have predicted the level of leakage and compared it with the expected signal. Through the simulations and observations, we have come to a clear understanding of one of the main obstacles in detecting the signal, and our results will be useful for any current or future 21cm signal detection experiments.