Pōniuā‘ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole

Abstract

We report the discovery of a luminous quasar, J1007+2115 at z = 7.515 ("Pōniuā'ena"), from our wide-field reionization-era quasar survey. J1007+2115 is the second quasar now known at z > 7.5, deep into the reionization epoch. The quasar is powered by a (1.5 ± 0.2) × 10 9 M supermassive black hole (SMBH), based on its broad Mg II emission-line profile from Gemini and Keck near-IR spectroscopy. The SMBH in J1007+2115 is twice as massive as that in quasar J1342+0928 at z = 7.54, the current quasar redshift record holder. The existence of such a massive SMBH just 700 million years after the Big Bang significantly challenges models of the earliest SMBH growth. Model assumptions of Eddington-limited accretion and a radiative efficiency of 0.1 require a seed black hole of 10 4 M at z = 30. This requirement suggests either a massive black hole seed as a result of direct collapse or earlier periods of rapid black hole growth with hyper-Eddington accretion and/or a low radiative efficiency. We measure the damping wing signature imprinted by neutral hydrogen absorption in the intergalactic medium (IGM) on J1007+2115's Lyα line profile, and find that it is weaker than that of J1342+0928 and two other z 7 quasars. We estimate an IGM volume-averaged neutral fraction x HI = 0.39 +0.22 −0.13 . This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 µm [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of z = 7.5149 ± 0.0004 and indicates a star formation rate of ∼ 210 M yr −1 in its host galaxy.

Texas Spectroscopic Search for Lyα Emission at the End of Reionization I. Constraining the Lyα Equivalent-width Distribution at 6.0 < z < 7.0

“…Although our estimation of X HI is based on a simplified analytic approach, our inferred X HI is below those high H I fractions from other Lyα studies. However, it is consistent with the recent measurement of X HI = 39 +22 −13 % from the damping wing feature of a luminous z = 7.5 quasar observations in Yang et al (2020), showing that a lower X HI fraction is plausible at z > 7.…”

“…However, our result is consistent with what is predicted in Finkelstein et al (2019b) of X HI ∼ 0.3 +0.1 −0.1 at z = 7.6, under the assumption that the faintest galaxies dominate the ionizing photon budget. It is also consistent with the neutral fraction of X HI = 39 +22 −13 %, which is estimated from the damping wing analysis of a luminous z = 7.5 quasar observations in Yang et al (2020). Additionally, as discussed in Section 4.4, the estimated T Lyα IGM would be doubled with a lower intrinsic LAF of 50%, making corresponding X HI values even lower.…”

Radio detection of VIK J2318−3113, the most distant radio-loud quasar (z = 6.44)

“…has led to the discovery of thousands of high-z quasars (QSOs), with more than 200 sources discovered at z > 6 (e.g. Mazzucchelli et al 2017;Matsuoka et al 2019;Fan et al 2019;Wang et al 2019;Andika et al 2020), the three most distant of which are at z ∼ 7.5 (Bañados et al 2018;Yang et al 2020a;Wang et al 2021a). These sources have already proved to be very useful tools for investigating the intergalactic medium (IGM) at early cosmic times through the absorption of their optical spectra bluewards of Lyα (e.g.…”

Enhanced X-Ray Emission from the Most Radio-powerful Quasar in the Universe’s First Billion Years

“…The evolution of supermassive black holes (SMBHs) in the early universe represents a challenge for modern cosmology, requiring significant, sustained growth from primordial seeds to explain the population of observed quasars in the first billion years of the universe (e.g., Inayoshi et al 2020). In the past decade, not only has the number of known members of this population expanded through large surveys (e.g., Bañados et al 2016;Jiang et al 2016;Mazzucchelli et al 2017;Reed et al 2017;Matsuoka et al 2019;Wang et al 2019;Yang et al 2019), but individual discoveries have pushed out the extremes of mass (Wu et al 2015;Yang et al 2020), luminosity (Pons et al 2019;Medvedev et al 2020), and redshift (Mortlock et al 2011;Bañados et al 2018c;Wang et al 2021b) that must be accounted for by theoretical models. Grappling with this challenge requires not only measuring quasar accretion rates, but also identifying mechanisms being used to produce massive growth.…”