Journal or Publication Title:

Բյուրականի աստղադիտարանի հաղորդումներ: Երևանի աստղադիտարանի բյուլետեն = Сообщения Бюраканской обсерватории. Бюллетень ереванской Астрономической обсерватории = Contributions from the Burakan observatory. Bulletin of the Erevan astronomical observatory

Date of publication:

2026

Volume:

73

Number:

1

ISSN:

2579-2276

Coverage:

196-206

Abstract:

Supermassive black holes (SMBHs) with masses of 108–109 M⊙ are observed at redshifts z > 7– 10, corresponding to cosmic times less than 700 Myr after the Big Bang within ΛCDM cosmology. Recent JWST discoveries, including Little Red Dots (LRDs), compact galaxies hosting overmassive SMBHs, and dustobscured AGN (e.g., CAPERS-LRD-z9 at z ≃ 9.3), challenge light-seed models that rely solely on Eddingtonlimited accretion from stellar-mass remnants (Kocevski et al., 2025, Maiolino et al., 2024, Rusakov et al., 2026). While heavy-seed scenarios such as direct collapse partially alleviate growth timescale issues, they often require finely tuned initial conditions or episodic super-Eddington accretion to match the observed abundance and mass distribution of high-z SMBHs. Unlike existing heavy-seed models, this work proposes a phenomenological framework in which massive early seeds (Mseed ≥ 105–106M⊙) are treated as an effective macroscopic population constrained by observations, without invoking a single specific formation channel. Forming preferentially in highly biased overdense environments at z ≥15, these seeds act as gravitational centers that accelerate galaxy and quasar assembly, reducing the required growth from ≃18–20 e-folds to ≥10 while remaining consistent with realistic duty cycles and feedback physics. The model naturally explains the elevated MBH/M∗ ratios observed in compact high-redshift systems without extreme dust obscuration or feedback fine-tuning. We outline viable parameter ranges and present multiple independent observational tests, including an enhanced central SMBH occupation fraction in compact galaxies (testable with JWST programs such as GLIMPSE and PRIMER), relic intermediate-mass black hole populations, and elevated early merger rates detectable by LISA Consortium (2025). The framework is fully consistent with ΛCDM cosmology and does not modify global cosmological observables. It can be decisively tested or falsified with ongoing JWST deep fields, ngEHT observations, and future gravitational-wave measurements. In particular, the absence of an enhanced SMBH occupation fraction in the most compact high-redshift galaxies would directly falsify the model.

Format:

pdf

Identifier:

oai:arar.sci.am:439356

General note:

Communications of the Byurakan Astrophysical Observatory (ComBAO) is a peer-reviewed scientific journal, which publishes research in observational and theoretical astronomy/astrophysics and presents recent advances in these fields. It is being published by the NAS RA V. Ambartsumian Byurakan Astrophysical Observatory (BAO) in English in electronic form. The journal publishes original papers, review papers, brief reports, book reviews, special communications, observational and theoretical results in various fields of astronomy and related sciences, and some editorial notes, including anniversaries and obituaries. Under the heading “Legacy”, the renewed magazine will republish some old articles of high value in English. The heading “Guest articles” will bring to the attention of readers the articles of researchers who are not employees of BAO. ComBAO was founded in 1946 and regularly published in 1946-1990. However, the publication was interrupted because of the economic situation after the disintegration of the Soviet Union in 1991.

Location of original object:

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