Ansah-Narh, T; Abdalla, FB; Smirnov, OM; Asad, KMB; Shaw, JR; (2018) Simulations of systematic direction-dependent instrumental effects in intensity mapping experiments. Monthly Notices of the Royal Astronomical Society , 481 (2) pp. 2694-2710. 10.1093/mnras/sty2433.

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Abstract

Intensity mapping experiment treats the 21 cm radio emission as a diffuse source and allows smaller and relatively cheaper radio antennas with short baselines to be used in such experiments. However, the technique is restricted by the precise subtraction of the foreground continuum signal from Galactic and extragalactic radio sources. Furthermore, the signal is subjected to direction-dependent effects, particularly the primary beam, as it modulates the intensity as a function of the sky position. In addition, due to the imperfections in the antenna feeds, a portion of the polarized foreground tends to find its way into the total intensity, making it a major obstacle to detect the H I signal. In the case of dish arrays, this will be dominated by the instrument mispointings and polarization leakage. To estimate this contamination, we use OSKAR to simulate ‘dish-like’ primary beams and then perturb these primary beams by introducing gain, phase, and surface distribution errors. We then simulate the foregrounds with these modelled beams to determine the errors in Stokes I and also observe the amount of |Q + iU| that corrupts I. Our simulation shows that the H I signal power can be measured at a multipole moment of l = 100 if we do not correct for any polarization leakage of the beam and at a multiple moment of l = 25 if we correct for the beam from I, assuming the beam is not known to the extent to which we have considered in this paper.

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