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Ighina et al. report the 888 MHz radio detection in the Rapid ASKAP
Continuum Survey (RACS) of VIK J2318−3113, a z=6.44 quasar. The ratio
of its radio luminosity to its optical luminosity yields a radio
loudness of R∼70 (R= L_5GHz/L_4400Å), making it the most distant radio-loud
quasar observed to date. The large bolometric luminosity suggests the
presence of a supermassive black hole with mass of the order of a
billion solar masses when the Universe was less than a billion years
old. Comparing the new radio observation from RACS with archival
radio data at the same frequency suggests that the flux density of
the source has varied by a factor of ∼2, which is consistent with the
presence of a relativistic jet oriented towards the line of sight,
i.e., a blazar nature. The image above shows a 1 arcminute x 1
arcminute VIKING
(VISTA Kilo-degree Infrared Galaxy survey)
image centred on VIK J2318−3113, with the 888 MHz
radio contours from both RACS (continuous red lines) and GAMA23
(dashed blue lines) ASKAP observations overlaid. In the bottom-left
corner the beam sizes from the RACS (12.2" × 11.4") and GAMA23 (10.2"
× 8.5") observations are shown.
More details are available in
the preprint of the paper.
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