Abstract
Abstract Luminous z ≥ 7 quasars provide direct probes of the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR). The Lyα damping wing absorption imprinted by neutral hydrogen in the IGM can be detected in a single EoR quasar spectrum, allowing the measurement of the IGM neutral fraction toward that line of sight. However, damping wing features have only been detected in two z > 7 quasars in previous studies. In this paper, we present new high-quality optical and near-infrared spectroscopy of the z = 7.00 quasar DES J025216.64–050331.8 obtained with Keck/Near-Infrared Echellette Spectrometer and Gemini/GMOS. By using the Mg ii single-epoch virial method, we find that it hosts a SMBH accreting at an Eddington ratio of λ Edd = 0.7 ± 0.1, consistent with the values seen in other luminous z ∼ 7 quasars. Furthermore, the Lyα region of the spectrum exhibits a strong damping wing absorption feature. The lack of associated metal absorption in the quasar spectrum indicates that this absorption is imprinted by a neutral IGM. Using a state-of-the-art model developed by Davies et al., we measure a volume-averaged neutral hydrogen fraction at z = 7 of within 68% (95%) confidence intervals when marginalizing over quasar lifetimes of . This is the highest IGM neutral fraction yet measured using reionization-era quasar spectra.
Highlights
The earliest luminous quasars, powered by billion solar-mass supermassive black holes (SMBHs), can be used to constrain the physics of SMBH accretion and the assembly of the first generation of massive galaxies in the early universe, and to obtain critical information on the physical conditions of the intergalactic medium (IGM) during the epoch of reionization (EoR)
We present the detection of strong IGM damping wing absorption along the line of sight to a luminous z = 7 quasar DES J025216.64–050331.8, using new high-quality optical/near-infrared spectroscopic observations; we use the new spectrum to measure the mass and Eddington ratio of the central SMBH
If J0252–0503 has been accreting at such Eddington ratio since z ∼ 20 with a radiative efficiency of 10%, it would require a seed BH of ~105 M, which significantly exceeds the predicted mass range from stellar remnant BHs and requires more exotic seed formation mechanisms like direct collapse BHs
Summary
The earliest luminous quasars, powered by billion solar-mass supermassive black holes (SMBHs), can be used to constrain the physics of SMBH accretion and the assembly of the first generation of massive galaxies in the early universe, and to obtain critical information on the physical conditions of the intergalactic medium (IGM) during the epoch of reionization (EoR). Compared to other probes of reionization history, such as cosmic microwave background (CMB) polarization (Planck Collaboration et al 2018) and Lyα emission line visibility in high-redshift galaxies (e.g., Ouchi et al 2010; Mason et al 2018), a main advantage of IGM damping wing measurement is that it can be applied to individual quasar sight lines, thereby constraining the average neutral fraction, and its scatter in different regions of the IGM. We present the detection of strong IGM damping wing absorption along the line of sight to a luminous z = 7 quasar DES J025216.64–050331.8 (hereinafter J0252–0503; Yang et al 2019), using new high-quality optical/near-infrared spectroscopic observations; we use the new spectrum to measure the mass and Eddington ratio of the central SMBH.
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