Kavli Affiliate: John Silverman
| First 5 Authors: John Silverman, John Silverman, , ,
| Summary:
The relation between the masses of supermassive black holes (SMBHs) and their
host galaxies encodes information on their mode of growth, especially at the
earliest epochs. The James Webb Space Telescope (JWST) has opened such
investigations by detecting the host galaxies of AGN and more luminous quasars
within the first billion years of the universe (z > 6). Here, we evaluate the
relation between the mass of SMBHs and the total stellar mass of their host
galaxies using a sample of nine quasars at 6.18 < z < 6.4 from the Subaru
High-z Exploration of Low-luminosity Quasars (SHELLQs) survey with NIRCam and
NIRSpec observations. We find that the observed location of these quasars in
the SMBH-galaxy mass plane (log MBH ~ 8-9; log M* ~9.5-11) is consistent with a
non-evolving intrinsic mass relation with dispersion (0.80_-0.28^+0.23 dex)
higher than the local value (~0.3-0.4 dex). Our analysis is based on a forward
model of systematics and includes a consideration of the impact of selection
effects and measurement uncertainties, an assumption on the slope of the mass
relation, and finds a reasonable AGN fraction (2.3%) of galaxies at z ~ 6 with
an actively growing UV-unobscured black hole. In particular, models with a
substantially higher normalisation in MBH would require an unrealistically low
intrinsic dispersion (~0.22 dex) and a lower AGN fraction (~0.6%).
Consequently, our results predict a large population of AGNs at lower black
hole masses, as are now just starting to be discovered in focused efforts with
JWST.
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