Polarization leakage in epoch of reionization windows - II. Primary beam model and direction-dependent calibration

Asad, K.M.B.; Koopmans, L. V. E.; Jelić, Vibor; Ghosh, A.; Abdalla, F.B.; Brentjens, M. A.; de Bruyn, A. G.; Ciardi, B.; Gehlot, B.K.; Iliev, I. T.; Mevius, M.; Pandey, V.N.; Yatawatta, S.; Zaroubi, S. (2016) Polarization leakage in epoch of reionization windows - II. Primary beam model and direction-dependent calibration. Monthly notices of the Royal Astronomical Society, 462 (4). pp. 4482-4494. ISSN 0035-8711

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Abstract

Leakage of diffuse polarized emission into Stokes I caused by the polarized primary beam of the instrument might mimic the spectral structure of the 21-cm signal coming from the epoch of reionization (EoR) making their separation difficult. Therefore, understanding polarimetric performance of the antenna is crucial for a successful detection of the EoR signal. Here, we have calculated the accuracy of the nominal model beam of Low Frequency ARray (LOFAR) in predicting the leakage from Stokes I to Q, U by comparing them with the corresponding leakage of compact sources actually observed in the 3C 295 field. We have found that the model beam has errors of ≤10 per cent on the predicted levels of leakage of ˜1 per cent within the field of view, i.e. if the leakage is taken out perfectly using this model the leakage will reduce to 10-3 of the Stokes I flux. If similar levels of accuracy can be obtained in removing leakage from Stokes Q, U to I, we can say, based on the results of our previous paper, that the removal of this leakage using this beam model would ensure that the leakage is well below the expected EoR signal in almost the whole instrumental k-space of the cylindrical power spectrum. We have also shown here that direction-dependent calibration can remove instrumentally polarized compact sources, given an unpolarized sky model, very close to the local noise level.

Item Type:	Article
Uncontrolled Keywords:	polarization; instrumentation; interferometers techniques; interferometric techniques; polarimetric; telescopes; dark ages; reionization; first stars
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Divisions:	Division of Experimental Physics
Depositing User:	Vibor Jelić
Date Deposited:	10 Nov 2016 10:22
URI:	http://fulir.irb.hr/id/eprint/3110
DOI:	10.1093/mnras/stw1863

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