Cosmology with powerful radio-loud AGNs

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 \citeauthor{FR+1974} type-II radio sources based on their integrated flux density across a broad range of radio frequencies, and the angular size and axis 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 by between 15-35\% yet their fitted distances are the same to within 7\%. These distance estimates together yield a transverse comoving distance to Cygnus A of $261_{-55}^{+70}\mathrm{Mpc}$ corresponding to a Hubble constant of $H_0=64_{-13}^{+17}\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$. 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.

12 pages, 3 figures, 3 tables; accepted in MNRAS

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Cited by in corpus (8)

• The duty cycle of radio galaxies revealed by LOFAR: remnant and restarted radio source populations in the Lockman Hole
• RAiSE: simulation-based analytical model of AGN jets and lobes
• PRAiSE: Resolved spectral evolution in simulated radio sources
• Using variability and VLBI to measure cosmological distances
• RAiSE X: searching for radio galaxies in X-ray surveys
• The morphological classification of distant radio galaxies explored with three-dimensional simulations
• RAiSERed: radio continuum redshifts for lobed AGNs
• HST WFC3/Grism Observations of the Candidate Ultra-High-Redshift Radio Galaxy GLEAM J0917-0012