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<p>Understanding the rapid formation of supermassive black holes in the early Universe requires insights 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 &gt; 6, both hosting moderate-luminosity quasars. These galaxies exhibit Balmer absorption lines, like low-redshift post-starburst galaxies. Our analyses of the medium-resolution spectra and multiband photometry show that the bulk of the stellar mass (log(<i>M</i><sub>*</sub>/<i>M</i><sub>☉</sub>) ≥ 10.6) formed in starburst episodes at redshift 9 and 7. One of the galaxies shows a clear Balmer break and lacks spatially resolved Hα emission. It falls well below the star-formation main sequence at <i>z</i> = 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 <span>iii</span>] emission lines indicate quasar-driven outflow, which possibly influences star formation. Direct stellar velocity dispersion measurements reveal that one galaxy follows the local black hole mass versus <i>σ</i><sub>*</sub> relation whereas the other is overmassive. The existence of massive post-starburst galaxies hosting billion-solar-mass black holes in short-lived quasar phases indicates that supermassive black holes and host galaxies played a principal role in each other’s rapid early formation.</p>

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A post-starburst pathway for the formation of massive galaxies and black holes at z > 6

  • 期刊论文

  • 发表日期：

    2025年8月11日

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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

摘要

Understanding the rapid formation of supermassive black holes in the early Universe requires insights 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, like low-redshift post-starburst galaxies. Our analyses of the medium-resolution spectra and multiband photometry show that the bulk of the stellar mass (log(M*/M☉) ≥ 10.6) formed in starburst episodes at redshift 9 and 7. One of the galaxies shows a clear Balmer break and lacks spatially resolved Hα 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 indicate quasar-driven outflow, which possibly influences star formation. Direct stellar velocity dispersion measurements reveal that one galaxy follows the local black hole mass versus σ* relation whereas the other is overmassive. The existence of massive post-starburst galaxies hosting billion-solar-mass black holes in short-lived quasar phases indicates that supermassive black holes and host galaxies played a principal role in each other’s rapid early formation.