A Post-Starburst Pathway for the Formation of Massive Galaxies and Black Holes at z>6

Understand

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.