S21A0044

Previous studies of the highest-redshift (z > 6) quasars revealed large supermassive black holes (SMBHs) with M_BH =10⁹⁻¹⁰ M_⊙ accreting at the Eddington limit. Those SMBHs grow faster than their host galaxies compared to the relation known in the local universe, and their broad-line-regions (BLRs) are metal-rich up to z=7.5. However, those trends are biased towards the most luminous quasars. Our initial studies of ∼1 dex fainter quasars from the Subaru/HSC survey revealed less massive and less active SMBHs, whose SMBH - dynamical mass ratios seems to trace the local co-evolutionary relation with a large scatter. We propose SWIMS NIR spectroscopy of additional six low-luminosity quasars at 6.15≤ z ≤ 6.69 as a first step toward the full census of z>6 quasars. A large and complete sample covering a wide luminosity/mass range will reveal the distributions of the Mgii-based SMBH masses, Eddington ratios, and the SMBH-dynamical mass ratios with our ALMA observations targeting the same quasars. Various metal emission lines are covered thanks to the wide spectral coverage, from which the nuclear-scale outflows and the BLR metallicity can be investigated. Those SMBH/host properties and their correlations help us to fully understand the early SMBH growth.

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