University Of Tasmania
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Radio Galaxy Zoo: cosmological alignment of radio sources

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journal contribution
posted on 2023-05-19, 09:09 authored by Contigiani, O, de Gasparin, F, Miley, GK, Rudnick, L, Andernach, H, Banfield, JK, Kapinska, AD, Stanislav ShabalaStanislav Shabala, Wong, OI
We study the mutual alignment of radio sources within two surveys, Faint Images of the Radio Sky at Twenty-centimetres (FIRST) and TIFR GMRT Sky Survey (TGSS). This is done by producing two position angle catalogues containing the preferential directions of respectively 30 059 and 11 674 extended sources distributed over more than 7000 and 17 000 deg2. The identification of the sources in the FIRST sample was performed in advance by volunteers of the Radio Galaxy Zoo (RGZ) project, while for the TGSS sample it is the result of an automated process presented here. After taking into account systematic effects, marginal evidence of a local alignment on scales smaller than 2.5 deg is found in the FIRST sample. The probability of this happening by chance is found to be less than 2 per cent. Further study suggests that on scales up to 1.5 deg the alignment is maximal. For one third of the sources, the RGZ volunteers identified an optical counterpart. Assuming a flat Λ cold dark matter cosmology with Ωm=0.31,ΩΛ=0.69 Ωm=0.31,ΩΛ=0.69 , we convert the maximum angular scale on which alignment is seen into a physical scale in the range [19, 38] Mpc h−170 h70−1 . This result supports recent evidence reported by Taylor and Jagannathan of radio jet alignment in the 1.4 deg2 ELAIS N1 field observed with the Giant Metrewave Radio Telescope. The TGSS sample is found to be too sparsely populated to manifest a similar signal.


Australian Research Council


Publication title

Monthly notices of the Royal Astronomical Society








School of Natural Sciences


Blackwell Publishing Ltd

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9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

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This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2017 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Expanding knowledge in the physical sciences