Discovery of the most luminous quasar of the last 9 Gyr

Abstract

We report the discovery of a bright (g = 14.5 mag (AB), K = 11.9 mag (Vega)) quasar at redshift z = 0.83 -- the optically brightest (unbeamed) quasar at z > 0.4. SMSS J114447.77-430859.3, at a Galactic latitude of b = +18.1deg, was identified by its optical colours from the SkyMapper Southern Survey (SMSS) during a search for symbiotic binary stars. Optical and near-infrared spectroscopy reveals broad MgII, H-beta, H-alpha, and Pa-beta emission lines, from which we measure a black hole mass of log10(M_BH/M_Sun) = 9.4 +/- 0.5. With its high luminosity, L_bol = (4.7 +/- 1.0) * 10^47 erg/s or M_i(z=2) = -29.74 mag (AB), we estimate an Eddington ratio of ~1.4. As the most luminous quasar known over the last ~9 Gyr of cosmic history, having a luminosity 8 times greater than 3C 273, the source offers a range of potential follow-up opportunities.

13 pages. Accepted for publication in PASA

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Cited by in corpus (3)

• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The accretion of a solar mass per day by a 17-billion solar mass black hole
• The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in the last 9 Gyr