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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 $b=+18.1^{\circ}$ , 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 Mg II, H $\unicode{x03B2}$ , H $\unicode{x03B1}$ , and Pa $\unicode{x03B2}$ emission lines, from which we measure a black hole mass of $\log_{10}\! (M_{BH}/M_{\odot}) = 9.4 ± 0.5$ . With its high luminosity, $L_{bol} = (4.7±1.0)×10^{47} erg s^{-1}$ or $Mi(z=2) = -29.74$ 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 $8×$ greater than 3C 273, the source offers a range of potential follow-up opportunities.
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Submitted on : Friday, November 4, 2022 - 2:43:37 PM
Last modification on : Sunday, November 6, 2022 - 3:04:31 AM

Citation

Christopher A. Onken, Samuel Lai, Christian Wolf, Adrian B. Lucy, Wei Jeat Hon, et al.. Discovery of the most luminous quasar of the last 9 Gyr. Publications of the Astronomical Society of Australia, 2022, 39, ⟨10.1017/pasa.2022.36⟩. ⟨insu-03839677⟩

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