Abstract
Quasars are the most luminous non-transient objects known, and as such, they
enable unparalleled studies of the universe at the earliest cosmic epochs.
However, despite extensive efforts from the astronomical community, the quasar
ULASJ1120+0641 at z=7.09 (hereafter J1120+0641) has remained as the only one
known at z>7 for more than half a decade. Here we report observations of the
quasar ULAS J134208.10+092838.61 (hereafter J1342+0928) at a redshift of
z=7.54. This quasar has a bolometric luminosity of 4e13 Lsun and a black hole
mass of 8e8 Msun. The existence of this supermassive black hole when the
universe was only 690 Myr old, i.e., just 5% its current age, reinforces early
black hole growth models that allow black holes with initial masses >1e4 Msun
or episodic hyper-Eddington accretion. We see strong evidence of the quasar's
Ly-alpha emission line being absorbed by a Gunn-Peterson damping wing from the
intergalactic medium, as would be expected if the intergalactic hydrogen
surrounding J1342+0928 is significantly neutral. We derive a significant
neutral fraction, although the exact value depends on the modeling. However,
even in our most conservative analysis we find xHI>0.33 (xHI>0.11) at 68% (95%)
probability, indicating that we are probing well within the reionization epoch.
Description
[1712.01860] An 800 million solar mass black hole in a significantly neutral universe at redshift 7.5
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