Radio detection of VIK J2318−3113, the most distant radio-loud quasar (z = 6.44)
Abstract
We report the 888 MHz radio detection in the Rapid ASKAP Continuum Survey (RACS) of VIK J2318−3113, a z = 6.44 quasar. Its radio luminosity (1.2 × 1026 W Hz−1 at 5 GHz) compared to the optical luminosity (1.8 × 1024 W Hz−1 at 4400 Å) makes it the most distant radio-loud quasar observed so far, with a radio loudness R ∼ 70 (R = L5 GHz/L4400 Å). Moreover, the high bolometric luminosity of the source (Lbol = 7.4 × 1046 erg s−1) suggests the presence of a supermassive black hole with a high mass (≳6 × 108 M⊙) at a time when the Universe was younger than a billion years. Combining the new radio data from RACS with previous ASKAP observations at the same frequency, we found that the flux density of the source may have varied by a factor of ∼2, which could suggest the presence of a relativistic jet oriented towards the line of sight, that is, a blazar nature. However, currently available radio data do not allow us to firmly characterise the orientation of the source. Further radio and X-ray observations are needed.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 2021
- DOI:
- 10.1051/0004-6361/202140362
- arXiv:
- arXiv:2101.11371
- Bibcode:
- 2021A&A...647L..11I
- Keywords:
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- galaxies: active;
- galaxies: high-redshift;
- galaxies: jets;
- quasars: general;
- quasars: individual: VIK J231818.3-311346;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 5 pages, 2 figures, 3 tables. Accepted for publication in A&