Little red dots (LRDs) are a high redshift galaxy population. Despite their high number densities, their nature is still uncertain. Here we present CANUCS-LRD-z8.6, a spectroscopically confirmed little red dot at a spectroscopic redshift of zspec = 8.6319, hosting an active galactic nucleus. Its spectrum exhibits broad Hβλ4863 Å emission, high-ionization lines (C iv, N iv]), high electron temperature, which are indicative of active galactic nucleus activity, and low metallicity (Z < 0.1−0.2Z⊙). The inferred black hole mass, <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="41467_2025_65070_Article_IEq1.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="175" /> </InlineMediaObject> <EquationSource Format="TEX">${M}_{{{{\rm{BH}}}}}=1.{0}_{-0.4}^{+0.6}\times 1{0}^{8}\,{{{{\rm{M}}}}}_{\odot }$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi>M</mi> </mrow> <mrow> <mi mathvariant="normal">BH</mi> </mrow> </msub> <mo>=</mo> <mn>1</mn> <mo>.</mo> <msubsup> <mrow> <mn>0</mn> </mrow> <mrow> <mo>−</mo> <mn>0.4</mn> </mrow> <mrow> <mo>+</mo> <mn>0.6</mn> </mrow> </msubsup> <mo>×</mo> <mn>1</mn> <msup> <mrow> <mn>0</mn> </mrow> <mrow> <mn>8</mn> </mrow> </msup> <mspace width="0.25em" /> <msub> <mrow> <mi mathvariant="normal">M</mi> </mrow> <mrow> <mo>⊙</mo> </mrow> </msub> </math></EquationSource> </InlineEquation>, poses strong constraints on current black hole formation models and simulations. Additionally, its black hole is over-massive relative to its host, deviating from local MBH − M* relations, suggesting an early, rapid black hole growth preceding that of its galaxy. CANUCS-LRD-z8.6 may represent an evolutionary link between early massive black holes and the luminous quasars observed at z = 6.

Extreme properties of a compact and massive accreting black hole host in the first 500 Myr

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2025年11月19日

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Roberta Tripodi,
Nicholas Martis,
Vladan Markov,
Maruša Bradač,
Fabio Di Mascia,
Vieri Cammelli,
Francesco D’Eugenio,
Chris Willott,
Mirko Curti,
Maulik Bhatt,
Simona Gallerani,
Gregor Rihtaršič,
Jasbir Singh,
Gaia Gaspar,
Anishya Harshan,
Jon Judež,
Rosa M. Merida,
Guillaume Desprez,
Marcin Sawicki,
Ilias Goovaerts,
Adam Muzzin,
Gaël Noirot,
Ghassan T. E. Sarrouh,
Roberto Abraham,
Yoshihisa Asada,
Gabriel Brammer,
Vicente Estrada-Carpenter,
Giordano Felicioni,
Seiji Fujimoto,
Kartheik Iyer,
Lamiya Mowla,
Victoria Strait

摘要

Little red dots (LRDs) are a high redshift galaxy population. Despite their high number densities, their nature is still uncertain. Here we present CANUCS-LRD-z8.6, a spectroscopically confirmed little red dot at a spectroscopic redshift of z_spec = 8.6319, hosting an active galactic nucleus. Its spectrum exhibits broad Hβλ4863 Å emission, high-ionization lines (C iv, N iv]), high electron temperature, which are indicative of active galactic nucleus activity, and low metallicity (Z < 0.1−0.2Z_⊙). The inferred black hole mass, ${M}_{{{{\rm{BH}}}}}=1.{0}_{-0.4}^{+0.6}\times 1{0}^{8}\,{{{{\rm{M}}}}}_{\odot }$ $M_{BH} = 1 . 0_{- 0.4}^{+ 0.6} \times 1 0^{8} M_{⊙}$ , poses strong constraints on current black hole formation models and simulations. Additionally, its black hole is over-massive relative to its host, deviating from local M_BH − M_* relations, suggesting an early, rapid black hole growth preceding that of its galaxy. CANUCS-LRD-z8.6 may represent an evolutionary link between early massive black holes and the luminous quasars observed at z = 6.