A1 Refereed original research article in a scientific journal
Using variability and VLBI to measure cosmological distances
Authors: Hodgson JA, L'Huillier B, Liodakis I, Lee SS, Shafieloo A
Publisher: OXFORD UNIV PRESS
Publication year: 2020
Journal:: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume: 495
Issue: 1
First page : L27
Last page: L31
Number of pages: 5
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnrasl/slaa051
Self-archived copy’s web address: https://research.utu.fi/converis/portal/Publication/51191412
In this paper, we propose a new approach to determining cosmological distances to active Galactic nuclei (AGNs) via light travel-time arguments, which can be extended from nearby sources to very high redshift sources. The key assumption is that the variability seen in AGNs is constrained by the speed of light and therefore provides an estimate of the linear size of an emitting region. This can then be compared with the angular size measured with very long baseline interferometryer to derive a distance. We demonstrate this approach on a specific well-studied low-redshift (z = 0.0178) source 3C 84 (NGC 1275), which is the bright radio core of the Perseus Cluster. We derive an angular diameter distance including statistical errors of D-A = 72(-6)(+5) Mpc for this source, which is consistent with other distance measurements at this redshift. Possible sources of systematic errors and ways to correct for them are discussed.
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