Cosmology with powerful radio-loud AGNs. (arXiv:1903.12308v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Turner_R/0/1/0/all/0/1">Ross Turner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shabala_S/0/1/0/all/0/1">Stanislav Shabala</a>
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 $261_{-55}^{+70}rm, Mpc$
corresponding to a Hubble constant of $H_0 = 64_{-13}^{+17}rm, km, s^{-1},
Mpc^{-1}$. 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.
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 $261_{-55}^{+70}rm, Mpc$
corresponding to a Hubble constant of $H_0 = 64_{-13}^{+17}rm, km, s^{-1},
Mpc^{-1}$. 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.
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