Are early black holes too massive for their host galaxies? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Are early black holes too massive for their host galaxies?
Plain
In nearby galaxies a central black hole weighs about a thousandth of the galaxy's stars, but standard estimates for early JWST black holes give ten to a hundred times more. These estimates may be wrong if dense gas widens the spectral lines used to weigh them.
Precise · changed · core
Revision 1: For broad-line AGN at $z > 4$, including little red dots, determine whether $M_{\mathrm{BH}}/M_{*}$ exceeds the local value $\sim 10^{-3}$ by factors 10-100 as single-epoch virial estimates ($M_{\mathrm{BH}}$ from FWHM of H-alpha or H-beta and luminosity) imply, or whether electron scattering and radiative transfer in dense gas broaden the lines and inflate $M_{\mathrm{BH}}$. The answer is a calibrated $M_{\mathrm{BH}}-M_{*}$ relation at $z > 4$ with $M_{\mathrm{BH}}$ measured independently of the virial line-width method.
Revision 2: For broad-line AGN at $z > 4$, including little red dots, determine whether $M_{\mathrm{BH}}/M_{*}$ exceeds the local value $\sim 10^{-3}$ by factors 10-100 as single-epoch virial estimates ($M_{\mathrm{BH}}$ from FWHM of $\mathrm{H}-\alpha$ or $\mathrm{H}-\beta$ and luminosity) imply, or whether electron scattering and radiative transfer in dense gas broaden the lines and inflate $M_{\mathrm{BH}}$. The answer is a calibrated $M_{\mathrm{BH}}-M_{*}$ relation at $z > 4$ with $M_{\mathrm{BH}}$ measured independently of the virial line-width method.
Settled by
Spatially resolved stellar or gas dynamics (JWST, ALMA, ELT-class telescopes) or reverberation mapping of $z > 4$ broad-line AGN, compared with virial estimates for the same objects.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
contested
Status note
Rusakov et al. (Nature, 2026, arXiv:2503.16595) argued that electron scattering in dense ionized cocoons broadens the lines, giving $M_{\mathrm{BH}} \sim 10^{5}-10^{7} M_{\mathrm{sun}}$, about 100 times below virial estimates; this is disputed.
Posed since
2023

Decisions