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 $(1.5\pm 0.2)\times 10^9$ $M_{\odot }$ supermassive black hole (SMBH), based on its broad MgII 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 $\gtrsim 10^4$ $M_{\odot }$ 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 Ly$\alpha$ line profile, and find that it is weaker than that of J1342+0928 and two other $z\gtrsim 7$ quasars. We estimate an IGM volume-averaged neutral fraction $⟨x{}_{\mathrm{HI}}⟩=0.39_{-0.13}^{+0.22}$. This range of values suggests a patchy reionization history toward different IGM sightlines. We detect the 158 $\mu$m [C II] emission line in J1007+2115 with ALMA; this line centroid yields a systemic redshift of $z=7.5149\pm 0.0004$ and indicates a star formation rate of $\sim 210$ $M_{\odot }$ yr${}^{-1}$ in its host galaxy.

9 pages, 4 figures, ApJL in press

References in corpus (13)

• A luminous quasar at a redshift of z = 7.085
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• Model-independent evidence in favor of an end to reionization by z~6
• unWISE: unblurred coadds of the WISE imaging
• 350 Micron Dust Emission from High Redshift Quasars
• Physical properties of 15 quasars at $z\gtrsim 6.5$
• Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey
• Fe II Emission in 14 Low-Redshift Quasars: I - Observations
• A Significantly Neutral Intergalactic Medium Around the Luminous z=7 Quasar J0252-0503
• The identification of z-dropouts in Pan-STARRS1: three quasars at 6.5<z<6.7
• The UKIRT Hemisphere Survey: Definition and J-band Data Release
• Copious Amounts of Dust and Gas in a z=7.5 Quasar Host Galaxy
• Three new VHS-DES Quasars at 6.7 < z < 6.9 and Emission Line Properties at z > 6.5

Cited by in corpus (3)

• The discovery of a highly accreting, radio-loud quasar at z=6.82
• Radio Detection of VIK J2318$-$3113, the Most Distant Radio-Loud Quasar ($z$=6.44)
• Resolving the Radio Emission from the Quasar P172+18 at $z=6.82$