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5th of February 2021
ASKAP detection of the most distant radio-loud quasar
by Ighina et al.
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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