Polarization leakage in epoch of reionization windows - I. Low frequency array observations of the 3C196 field

K. M.B. Asad, L. V.E. Koopmans, V. Jelić, V. N. Pandey, A. Ghosh, F. B. Abdalla, G. Bernardi, M. A. Brentjens, A. G. De Bruyn, S. Bus, B. Ciardi, E. Chapman, S. Daiboo, E. R. Fernandez, G. Harker, I. T. Iliev, H. Jensen, O. Martinez-Rubi, G. Mellema, M. MeviusA. R. Offringa, A. H. Patil, J. Schaye, R. M. Thomas, S. Van Der Tol, H. K. Vedantham, S. Yatawatta, S. Zaroubi

פרסום מחקרי: פרסום בכתב עתמאמרביקורת עמיתים


Detection of the 21-cm signal coming from the epoch of reionization (EoR) is challenging especially because, even after removing the foregrounds, the residual Stokes I maps contain leakage from polarized emission that can mimic the signal. Here, we discuss the instrumental polarization of Low Frequency Array (LOFAR) and present realistic simulations of the leakages between Stokes parameters. From the LOFAR observations of polarized emission in the 3C196 field, we have quantified the level of polarization leakage caused by the nominal model beam of LOFAR, and compared it with the EoR signal using power spectrum analysis. We found that at 134-166 MHz, within the central 4° of the field the (Q, U)→I leakage power is lower than the EoR signal at k < 0.3 Mpc-1. The leakage was found to be localized around a Faraday depth of 0, and the rms of the leakage as a fraction of the rms of the polarized emission was shown to vary between 0.2 and 0.3 per cent, both of which could be utilized in the removal of leakage. Moreover, we could define an 'EoR window' in terms of the polarization leakage in the cylindrical power spectrum above the point spread function (PSF)-induced wedge and below k ~0.5Mpc-1, and the window extended up to k ~1Mpc-1 at all k{box drawings light up and horizontal} when 70 per cent of the leakage had been removed. These LOFAR results show that even a modest polarimetric calibration over a field of view of ≲ 4° in the future arrays like Square Kilometre Array will ensure that the polarization leakage remains well below the expected EoR signal at the scales of 0.02-1 Mpc-1.

שפה מקוריתאנגלית
עמודים (מ-עד)3709-3727
מספר עמודים19
כתב עתMonthly Notices of the Royal Astronomical Society
מספר גיליון4
מזהי עצם דיגיטלי (DOIs)
סטטוס פרסוםפורסם - 21 אוג׳ 2015
פורסם באופן חיצוניכן

הערה ביבליוגרפית

Publisher Copyright:
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

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