A powerful (and likely young) radio-loud quasar at z = 5.3
Abstract
We present the discovery of PSO J191.05696+86.43172 (hereafter PSO J191+86), a new powerful radio-loud quasar (QSO) in the early Universe (z = 5.32). We discovered it by cross-matching the NRAO VLA Sky Survey (NVSS) radio catalog at 1.4 GHz with the first data release of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS PS1) in the optical. With a NVSS flux density of 74.2 mJy, PSO J191+86 is one of the brightest radio QSO discovered at z ∼ 5. The intensity of its radio emission is also confirmed by the very high value of radio loudness (R > 300). The observed radio spectrum of PSO J191+86 shows a possible turnover around ∼1 GHz (i.e., ∼6 GHz in the rest frame), making it a gigahertz-peaked spectrum (GPS) source. However, variability could affect the real shape of the radio spectrum, because the data in hand were taken ∼25 years apart. By assuming a peak in the observed radio spectrum between 1 and 2 GHz (i.e., ∼6 and 13 GHz in the rest-frame) we find a linear size of the source of ∼10-30 pc and a corresponding kinetic age of 150-460 yr. This would make PSO J191+86 a newly born radio source. However, the large X-ray luminosity (5.3×1045 erg s−1), the flat X-ray photon index (ΓX = 1.32), and the optical-X-ray spectral index (αox̃ = 1.329) are typical of blazars. This could indicate that the nonthermal emission of PSO J191+86 is Doppler boosted. Further radio observations (both on arcsec and parsec scales) are necessary to better investigate the nature of this powerful radio QSO.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- January 2023
- DOI:
- 10.1051/0004-6361/202243855
- arXiv:
- arXiv:2210.14946
- Bibcode:
- 2023A&A...669A.134B
- Keywords:
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- galaxies: active;
- galaxies: high-redshift;
- galaxies: jets;
- quasars: supermassive black holes;
- quasars: individual: PSO J191.05696+86.43172;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 10 pages, 9 figures, 5 tables, Accepted for publication in A&