Kavli Affiliate: Robert A. Simcoe
| First 5 Authors: Madeline A. Marshall, Minghao Yue, Anna-Christina Eilers, Jan Scholtz, Michele Perna
| 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 $sim10^{10}M_odot$, suggesting
that this is a major galaxy interaction. Through detailed quasar subtraction
and SED fitting using the NIRCam data, we obtain 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 estimate a virial black hole mass of
$M_{rm{BH}}=(1.9^{+2.9}_{-1.1})times10^9 M_odot$. Thus, J1120+0641 has an
extreme black hole-stellar mass ratio of
$M_{rm{BH}}/M_ast=0.63^{+0.54}_{-0.31}$, 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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