Searching for Reionization-Era Quasars


In order to direct probe the evolution of the first generation SMBHs, the co-evolution between SMBHs and their host galaxy, and the cosmic reionization history, a large statistical quasars in the epoch of reionization (EoR) is needed. However, efforts to find such high redshift objects have proven to be challenging, because of a combination of their declining spatial density and the limited sky coverage of near-infrared (NIR) surveys. Moreover, more than half of know quasars at z>6.5 are not bright enough for detailed investigations with current facilities.
From 2016, I and my collaborators have started a major effort in establishing the first large luminous z ≳ 7 quasar sample. Combining the optical, near-infrared (NIR), and mid-infrared (MIR) photometry from DECalS, BASS+MzLS, PS1, DES, UHS, VHS, and WISE (unWISE), we are surveying z ~ 7 quasars in a wide field of ~ 20,000 square degree sky area, including ~15000 square degree field in the North and ~ 5000 square degree field in the Southern Sky.
Our new survey has already made the following remarkable achievements:

  • The Redshift Record Holder Quasar at z=7.6.

    • We recently discovered a new quasar at z = 7.6, the most distant quasar ever known. Dating back to just 670 million years after the big bang, the quasar hosts a supermassive black hole equivalent to the combined mass of 1.6 billion suns. The existence of such a massive SMBH challenges theoretical models of SMBH growth. Multi-wavelength followup observations are undertaking.
    Press release

  • The Luminous Quasar Hosting Massive BH at z=7.5.

    • We also discovered a luminous quasar at z=7.515 (Yang et al. 2020). It is more luminous than the previous redshift record holder J1342+0928 at z=7.54 (Banados et al. 2018) and hosts a two times more massive SMBH than J1342+0928, significantly challenging the earliest SMBHs growth. Moreover, we find that the damping wing signature which imprinted by neutral hydrogen is much weaker than that of J1342+0928 and other two z~7 quasars, suggesting that the cosmic reionization is very patchy.
    Press release

  • The Most Distant Gravitationally Lensed Quasar at z=6.5.

    • From our survey, we discovered a strong gravitationally lensed quasar at z=6.5188, the first such object discovered in the EoR and the brightest z > 6 object in both optical and IR (Fan et al. 2019; Yang et al. 2019b). This discovery also suggests a large population of lensed quasars missed by previous surveys due to selection bias.
    Press release

  • A Large Statistical Quasar Sample in the EoR.

    • In addition, our survey has yield more than 35 quasars at z ~ 6.5 - 7, including the most distant broad absorption quasar with high velocity outflows at z=7.02 and a z=7.00 quasar resides in a significant neutral environment (Yang et al. 2019a; Wang, Yang et al. 2018, 2019; Fan, Wang, Yang et al. 2019; Yang et al. in prep.).

  • The Quasar Population Evolves Fast in the EoR.

    • The quasar luminosity function measured based on this quasar sample indicate that the quasar density declines extremely fast at z>6.5 (Wang, Yang et al. 2019), suggesting that we are witnessing the first generation quasars in the EoR.

• Wang, Feige; Yang, Jinyi; Fan, Xiaohui, et al. 2021, ApJL A Luminous Quasar at Redshift 7.642
• Yang, Jinyi; Wang, Feige; Fan, Xiaohui, et al. 2020, ApJL Pōniuā'ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole
• Yang, Jinyi; Wang, Feige; Fan, Xiaohui, et al. 2019a, AJ Exploring Reionization-era Quasars. IV. Discovery of Six New z≳6.5 Quasars with DES, VHS, and unWISE Photometry
• Yang, Jinyi; Venemans, Bram; Wang, Feige, et al. 2019b, ApJ Far-infrared Properties of the Bright, Gravitationally Lensed Quasar J0439+1634 at z = 6.5
• Wang, Feige, Yang, Jinyi; Fan, Xiaohui; et al. 2019, ApJ Exploring Reionization-Era Quasars III: Discovery of 16 Quasars at 6.4≲z≲6.9 with DESI Legacy Imaging Surveys and UKIRT Hemisphere Survey and Quasar Luminosity Function at z~6.7
• Wang, Feige; Yang, Jinyi; Fan, Xiaohui, et al. 2018, ApJL The Discovery of A Luminous Broad Absorption Line Quasar at A Redshift of 7.02
• Fan, Xiaohui; Wang, Feige; Yang, Jinyi, et al. 2019, ApJL The Discovery of a Gravitationally Lensed Quasar at z = 6.51
• Bañados, Eduardo; ...; Yang, Jinyi et al. 2018, Nature An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5
• Wang, Feige; Fan, Xiaohui; Yang, Jinyi, et al. 2017, ApJ First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey
• Wu, Xue-Bing; ...; Yang, Jinyi, et al. 2015, Nature An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30