Universität zu Köln

Ma, Yik Ki ORCID: 0000-0003-0742-2006, Mao, S. A., Stil, Jeroen, Basu, Aritra ORCID: 0000-0003-2030-3394, West, Jennifer, Heiles, Carl, Hill, Alex S. and Betti, S. K. (2019). A broad-band spectro-polarimetric view of the NVSS rotation measure catalogue - II. Effects of off-axis instrumental polarization. Mon. Not. Roy. Astron. Soc., 487 (3). S. 3454 - 3470. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

The NRAO VIA Sky Survey (NVSS) rotation measure (RM) catalogue has enabled numerous studies in cosmic magnetism, and will continue being a unique data set complementing future polarization surveys. Robust comparisons with these new surveys will however require further understandings in the systematic effects present in the NVSS KM catalogue, In this paper, we make careful comparisons between our new on-axis broad-band observations with the Karl G, Jansky Very Large Array and the NVSS KM results for 23 sources. We found that two unpolarized sources were reported as polarized at about 0,5 per cent level in the RM catalogue, and noted significant differences between our newly derived KM values and the catalogue values for the remaining 21 sources. These discrepancies are attributed to off-axis instrumental polarization in the NVSS KM catalogue, By adopting the 0,5 per cent above as the typical off-axis instrumental polarization amplitude, we quantified its effect on the reported RMs with a simulation, and found that on average the RM uncertainties in the catalogue have to be increased by approximate to 10 per cent to account for the off-axis instrumental polarization effect. This effect is more substantial for sources with lower fractional polarization, and is a function of the source's true RM. Moreover, the distribution of the resulting RM uncertainty is highly non-Gaussian. With the extra RM uncertainty incorporated, we found that the RM values from the two observations for most (18 out of 21) of our polarized targets can be reconciled. The remaining three are interpreted as showing hints of time variabilities in RM.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Ma, Yik Ki UNSPECIFIED orcid.org/0000-0003-0742-2006 UNSPECIFIED Mao, S. A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stil, Jeroen UNSPECIFIED UNSPECIFIED UNSPECIFIED Basu, Aritra UNSPECIFIED orcid.org/0000-0003-2030-3394 UNSPECIFIED West, Jennifer UNSPECIFIED UNSPECIFIED UNSPECIFIED Heiles, Carl UNSPECIFIED UNSPECIFIED UNSPECIFIED Hill, Alex S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Betti, S. K. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-133780
DOI:	10.1093/mnras/stz1328
Journal or Publication Title:	Mon. Not. Roy. Astron. Soc.
Volume:	487
Number:	3
Page Range:	S. 3454 - 3470
Date:	2019
Publisher:	OXFORD UNIV PRESS
Place of Publication:	OXFORD
ISSN:	1365-2966
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language NRAO PMN SURVEYS; MAGNETIC-FIELD; RADIO-SOURCES; FARADAY-ROTATION; OPTICAL CATALOG; SKY; GHZ Multiple languages Astronomy & Astrophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13378