Kavli Affiliate: Robert A. Simcoe
| First 5 Authors: Dominika Ďurovčíková, Anna-Christina Eilers, Romain A. Meyer, Emanuele Paolo Farina, Eduardo Bañados
| Summary:
The existence of billion-solar-mass black holes hosted in luminous quasars
within the first gigayear of cosmic history poses a challenge to our
understanding of supermassive black hole (SMBH) growth. The problem is further
exacerbated by the very short quasar lifetimes of $t_{rm Q}lesssim 10^6$
years, as derived from the extent of their proximity zone (PZ) sizes observed
in the quasars’ rest-UV spectra. However, the quasar lifetime estimates based
on the extents of the proximity zones may be underestimated, as time-variable
obscuration effects might have limited the quasars’ emission along our
sightline in the past. In this work, we present independent quasar lifetime
measurements for six quasars at $z sim 6$ leveraging the extended nebular
emission perpendicular to our line-of-sight. We use observations from the Very
Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) to search for extended
Ly$alpha$ emission in the circumgalactic medium around quasars with small
proximity zones and estimate their lifetimes as the light travel time between
the SMBH and the outer edge of the nebula. We find agreement between the
independent lifetime estimates. For one object we find a proximate absorption
system prematurely truncating the extent of the quasar’s proximity zone, which
thus results in an expected discrepancy between the lifetime estimates. Our
results provide further evidence that the quasars’ current accretion episode
has only recently begun, challenging our models of SMBH growth.
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