2025-08-06 テキサス大学オースティン校（UT Austin）
Artist representation of CAPERS-LRD-z9, home to the earliest confirmed black hole. The supermassive black hole at its center is believed to be surrounded by a thick cloud of gas, giving the galaxy a distinctive red color. Image credit: Erik Zumalt, The University of Texas at Austin.
＜関連情報＞
- https://news.utexas.edu/2025/08/06/meet-the-universes-earliest-confirmed-black-hole-a-monster-at-the-dawn-of-time/
- https://iopscience.iop.org/article/10.3847/2041-8213/ade789
CAPERS-LRD-z9: ガスに包まれた小さな赤い点で、赤方偏移 z = 9.288 に位置する広線型活動銀河核を宿す天体 CAPERS-LRD-z9: A Gas-enshrouded Little Red Dot Hosting a Broad-line Active Galactic Nucleus at z = 9.288
Anthony J. Taylor, Vasily Kokorev, Dale D. Kocevski, Hollis B. Akins, Fergus Cullen, Mark Dickinson, Steven L. Finkelstein, Pablo Arrabal Haro, Volker Bromm, Mauro Giavalisco,…
The Astrophysical Journal Letters Published: 2025 August 6
DOI:10.3847/2041-8213/ade789
Abstract
We present CAPERS-LRD-z9, a little red dot (LRD) that we confirm to be a z = 9.288 broad-line active galactic nucleus (BLAGN). First identified as a high-redshift LRD candidate from PRIMER NIRCam photometry, follow-up NIRSpec/PRISM spectroscopy of CAPERS-LRD-z9 from the CANDELS-Area Prism Epoch of Reionization Survey (CAPERS) has revealed a broad 3500 km s−1 full width at half-maximum Hβ emission line and narrow [O iii] λλ4959, 5007 lines, indicative of a BLAGN. Based on the broad Hβ line, we compute a canonical black hole mass of log(MBH /M⊙)= 7.58± 0.15, although full consideration of systematic uncertainties yields a conservative range of 6.65<log(MBH /M⊙) <8.50. These observations suggest that either a massive black hole seed or a lighter stellar remnant seed undergoing periods of super-Eddington accretion is necessary to grow such a massive black hole in ≲500 Myr of cosmic time. CAPERS-LRD-z9 exhibits a strong Balmer break, consistent with a central AGN surrounded by dense (∼1010 cm−3) neutral gas. We model CAPERS-LRD-z9 using Cloudy to fit the emission redward of the Balmer break with a dense-gas-enshrouded AGN and bagpipes to fit the rest-ultraviolet emission as a host-galaxy stellar population. This upper limit on the stellar mass of the host galaxy (<109 M⊙) implies that the black hole to stellar mass ratio may be extremely large, possibly >5% (although systematic uncertainties on the black hole mass prevent strong conclusions). However, the shape of the UV continuum differs from typical high-redshift star-forming galaxies, indicating that this UV emission may also be of AGN origin; hence, the true stellar mass of the host may be still lower.
