Eight New Ultramassive Black Hole Masses confirm Best Correlation with Galaxy Core Sizes

Fuente: arXiv
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Auteurs principaux: de Nicola, Stefano, Thomas, Jens, Saglia, Roberto P., Kluge, Matthias, Snigula, Jan, Bender, Ralf
Format: Preprint
Publié: 2025
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author de Nicola, Stefano
Thomas, Jens
Saglia, Roberto P.
Kluge, Matthias
Snigula, Jan
Bender, Ralf
author_facet de Nicola, Stefano
Thomas, Jens
Saglia, Roberto P.
Kluge, Matthias
Snigula, Jan
Bender, Ralf
contents We analyse black-hole scaling relations at the high-mass end, focusing in particular on the regime of ultra-massive black holes, $\mathrm{M}_\mathrm{BH} > 10^{10}\,\mathrm{M}_\odot$ (UMBHs). In a sample of 16 Brightest Cluster Galaxies (BCGs) without previous black-hole mass measurements we discover 8 UMBHs based on direct dynamical detections with triaxial Schwarzschild models. This first sample of triaxial black-hole mass determinations increases the number of known UMBHs by a factor of two and dramatically increases the constraints for BH mass scaling relations at the high-mass end. We find that BCGs are outliers in the canonical BH - $σ$ relation, while the size of their depleted cores - the central light-deficient region - is a much better unbiased predictor of the black hole mass and should be used as a proxy at the high-mass end. BCGs smoothly join the trend already established for massive core galaxies in previous studies. This also holds for tight correlations between core size and sphere-of-influence radius and core size and core density. All these relations strongly support the black-hole binary model for the formation of the centers of the most massive galaxies.
format Preprint
id arxiv_https___arxiv_org_abs_2512_04178
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Eight New Ultramassive Black Hole Masses confirm Best Correlation with Galaxy Core Sizes
de Nicola, Stefano
Thomas, Jens
Saglia, Roberto P.
Kluge, Matthias
Snigula, Jan
Bender, Ralf
Astrophysics of Galaxies
We analyse black-hole scaling relations at the high-mass end, focusing in particular on the regime of ultra-massive black holes, $\mathrm{M}_\mathrm{BH} > 10^{10}\,\mathrm{M}_\odot$ (UMBHs). In a sample of 16 Brightest Cluster Galaxies (BCGs) without previous black-hole mass measurements we discover 8 UMBHs based on direct dynamical detections with triaxial Schwarzschild models. This first sample of triaxial black-hole mass determinations increases the number of known UMBHs by a factor of two and dramatically increases the constraints for BH mass scaling relations at the high-mass end. We find that BCGs are outliers in the canonical BH - $σ$ relation, while the size of their depleted cores - the central light-deficient region - is a much better unbiased predictor of the black hole mass and should be used as a proxy at the high-mass end. BCGs smoothly join the trend already established for massive core galaxies in previous studies. This also holds for tight correlations between core size and sphere-of-influence radius and core size and core density. All these relations strongly support the black-hole binary model for the formation of the centers of the most massive galaxies.
title Eight New Ultramassive Black Hole Masses confirm Best Correlation with Galaxy Core Sizes
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2512.04178