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Cosmology with powerful radio-loud AGNs

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posted on 2023-05-20, 09:49 authored by Ross TurnerRoss Turner, Stanislav ShabalaStanislav Shabala
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.

Funding

Australian Research Council

History

Publication title

Monthly Notices of the Royal Astronomical Society

Volume

486

Pagination

1225-1235

ISSN

0035-8711

Department/School

School of Natural Sciences

Publisher

Blackwell Publishing Ltd

Place of publication

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

Rights statement

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

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the physical sciences

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