Kavli Affiliate: Kohei Inayoshi
| First 5 Authors: Masafusa Onoue, Masafusa Onoue, , ,
| Summary:
Understanding the rapid formation of supermassive black holes (SMBHs) in the
early universe requires insight into stellar mass growth in host galaxies.
Here, we present NIRSpec rest-frame optical spectra and NIRCam imaging from
JWST of two galaxies at z>6, both hosting moderate-luminosity quasars. These
galaxies exhibit Balmer absorption lines, similar to low-redshift
post-starburst galaxies. Our analyses of the medium-resolution spectra and
multiband photometry show bulk of the stellar mass (log (M_* / M_sun) > 10.6)
formed in starburst episodes at redshift 9 and 7. One of the galaxies shows a
clear Balmer break and lacks spatially resolved H alpha emission. It falls well
below the star formation main sequence at z = 6, indicating quiescence. The
other is transitioning to quiescence; together, these massive galaxies are
among the most distant post-starburst systems known. The blueshifted wings of
the quasar [O III] emission lines suggest quasar-driven outflow possibly
influencing star formation. Direct stellar velocity dispersion measurements
reveal one galaxy follows the local black hole mass-sigma_* relation while the
other is overmassive. The existence of massive post-starburst galaxies hosting
billion-solar-mass BHs in short-lived quasar phases suggests SMBHs and host
galaxies played a major role in each other’s rapid early formation.
| Search Query: ArXiv Query: search_query=au:”Kohei Inayoshi”&id_list=&start=0&max_results=3