Kavli Affiliate: Roberto Maiolino
| First 5 Authors: , , , ,
| Summary:
The James Webb Space Telescope is revolutionising our ability to understand
the host galaxies and local environments of high-z quasars. Here we obtain a
comprehensive understanding of the host galaxy of the z=7.08 quasar J1120+0641
by combining NIRSpec integral field spectroscopy with NIRCam photometry of the
host continuum emission. Our emission-line maps reveal that this quasar host is
undergoing a merger with a bright companion galaxy. The quasar host and the
companion have similar dynamical masses of $sim10^10M_odot$, suggesting
that this is a major galaxy interaction. Through detailed quasar subtraction
and SED fitting using the NIRCam data, we obtained an estimate of the host
stellar mass of $M_ast=(3.0^+2.5_-1.4)times10^9M_odot$, with
$M_*=(2.7^+0.5_-0.5)times10^9M_odot$ for the companion galaxy. Using
the H$beta$ Balmer line we estimated a virial black hole mass of
$M_rmBH=(1.9^+2.9_-1.1)times10^9 M_odot$. Thus, J1120+0641 has an
extreme black hole-stellar mass ratio of
$M_rmBH/M_ast=0.63^+0.54_-0.31$, which is ~3 dex larger than expected
by the local scaling relations between black hole and stellar mass. J1120+0641
is powered by an overmassive black hole with the highest reported black
hole-stellar mass ratio in a quasar host that is currently undergoing a major
merger. These new insights highlight the power of JWST for measuring and
understanding these extreme first quasars.
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