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Cosmology with powerful radio-loud AGNs

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Turner, RJ ORCID: 0000-0002-4376-5455 and Shabala, SS ORCID: 0000-0001-5064-0493 2019 , 'Cosmology with powerful radio-loud AGNs' , Monthly Notices of the Royal Astronomical Society, vol. 486, no. 1 , pp. 1225-1235 , doi: 10.1093/mnras/stz922.

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Abstract

Immensely bright quasars and radio-loud active galactic nuclei (AGNs) provide an enticing opportunity to construct standard candles detectable up to the very early universe. An analytic theory is proposed to measure the distance to powerful Fanaroff & Riley type-II (FR-II) radio sources based on their integrated flux density across a broad range of radio frequencies, and the angular size and axial ratio of their synchrotron-emitting lobes. This technique can be used at low redshift to construct absolute standard candles in conjunction with X-ray observations of the host cluster, or at high redshift to measure the relative distances of objects and constrain the curvature of our Universe. Distances calculated with this method are consistent for dissimilar objects at the same redshift; the two lobes of Cygnus A have flux densities, linear sizes, and spectral break frequencies varying between 15 and 35 per cent yet their fitted distances are the same to within 7 per cent. These distance estimates together yield a transverse comoving distance to Cygnus A of 261+70-55 Mpc corresponding to a Hubble constant of H0 = 64+17-13 km s−1 Mpc−1. Large samples of suitable FR-II sources could provide a measure of the Hubble constant independent of existing techniques such as the cosmic microwave background, baryon acoustic oscillations, and type 1a supernovae.

Item Type: Article
Authors/Creators:Turner, RJ and Shabala, SS
Keywords: galaxies: active – galaxies: jets – cosmological parameters – distance scale – radio continuum: galaxies
Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
Publisher: Blackwell Publishing Ltd
ISSN: 0035-8711
DOI / ID Number: 10.1093/mnras/stz922
Copyright Information:

Copyright 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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