DETECTION OF SIGNALS FROM COSMIC REIONIZATION USING RADIO INTERFEROMETRIC SIGNAL PROCESSING

Observations of the H I 21 cm transition line promises to be an important probe into the cosmic dark ages and epoch of reionization. One of the challenges for the detection of this signal is the accuracy of the foreground source removal. This paper investigates the extragalactic point source contamination and how accurately the bright sources (∼>1 Jy) should be removed in order to reach the desired rms noise and be able to detect the 21 cm transition line. Here, we consider position and flux errors in the global sky model for these bright sources as well as the frequency independent residual calibration errors. The synthesized beam is the only frequency dependent term included here. This work determines the level of accuracy for the calibration and source removal schemes and puts forward constraints for the design of the cosmic reionization data reduction scheme for the upcoming low frequency arrays such as, Murchison Widefield Array, Precision Array to Probe Epoch of Reionization, etc. We show that in order to detect the reionization signal the bright sources need to be removed from the data sets with a positional accuracy of ∼0.1 arcsec. Our results also demonstrate that the efficient foreground source removal strategies can only tolerate a frequency independent antenna based mean residual calibration error of ∼<0.2% in amplitude or ∼<0.02 in phase, if they are constant over each days of observations (6 hr). In future papers, we will extend this analysis to the power-spectral domain and also include the frequency-dependent calibration errors and direction-dependent errors (ionosphere, primary beam, etc.).