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

Masafusa Onoue; Xuheng Ding; John D. Silverman; Yoshiki Matsuoka; Takuma Izumi; Michael A. Strauss; Charlotte Ward; Camryn L. Phillips; Kei Ito; Irham T. Andika; Kentaro Aoki; Junya Arita; Shunsuke Baba; Rebekka Bieri; Sarah E. I. Bosman; Anna-Christina Eilers; Seiji Fujimoto; Melanie Habouzit; Zoltan Haiman; Masatoshi Imanishi; Kohei Inayoshi; Kazushi Iwasawa; Knud Jahnke; Nobunari Kashikawa; Toshihiro Kawaguchi; Kotaro Kohno; Chien-Hsiu Lee; Junyao Li; Alessandro Lupi; Jianwei Lyu; Tohru Nagao; Roderik Overzier; Jan-Torge Schindler; Malte Schramm; Matthew T. Scoggins; Kazuhiro Shimasaku; Yoshiki Toba; Benny Trakhtenbrot; Maxime Trebitsch; Tommaso Treu; Hideki Umehata; Bram Venemans; Marianne Vestergaard; Marta Volonteri; Fabian Walter; Feige Wang; Jinyi Yang; Haowen Zhang

arXiv · 2409.07113

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

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Abstract

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.

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Masafusa Onoue, Xuheng Ding, John D. Silverman, Yoshiki Matsuoka, Takuma Izumi, Michael A. Strauss, Charlotte Ward, Camryn L. Phillips, Kei Ito, Irham T. Andika, Kentaro Aoki, Junya Arita, Shunsuke Baba, Rebekka Bieri, Sarah E. I. Bosman, Anna-Christina Eilers, Seiji Fujimoto, Melanie Habouzit, Zoltan Haiman, Masatoshi Imanishi, Kohei Inayoshi, Kazushi Iwasawa, Knud Jahnke, Nobunari Kashikawa, Toshihiro Kawaguchi, Kotaro Kohno, Chien-Hsiu Lee, Junyao Li, Alessandro Lupi, Jianwei Lyu, Tohru Nagao, Roderik Overzier, Jan-Torge Schindler, Malte Schramm, Matthew T. Scoggins, Kazuhiro Shimasaku, Yoshiki Toba, Benny Trakhtenbrot, Maxime Trebitsch, Tommaso Treu, Hideki Umehata, Bram Venemans, Marianne Vestergaard, Marta Volonteri, Fabian Walter, Feige Wang, Jinyi Yang, Haowen Zhang. 2024-09-11. A Post-Starburst Pathway for the Formation of Massive Galaxies and Black Holes at z>6. https://arxiv.org/abs/2409.07113

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