Study reveals new scaling relations between black hole mass and galaxy properties
Astronomers analyzed 151 galaxies with dynamically measured black hole masses to investigate how black hole mass relates to stellar velocity dispersion and core size. The research found that the relationship between black hole mass and core radius shows significantly less scatter than the traditional black hole mass-velocity dispersion relation, particularly at the highest masses. These findings suggest that ultramassive black holes in large galaxies may have grown through successive major mergers rather than following the standard scaling relations.
Using high-resolution Hubble Space Telescope imaging and dynamical measurements, researchers examined scaling relations between black hole mass and two galaxy properties: stellar velocity dispersion (σ) and the size of partially depleted cores (R_b). The study of 30 core-Sérsic galaxies established an updated M_BH-R_b relation with a power-law slope of 1.16±0.10 and reduced scatter compared to the M_BH-σ relation. At the highest black hole masses, the researchers identified a significant upturn in the M_BH-σ diagram driven by large-core galaxies hosting ultramassive black holes, which deviate substantially from the relation defined by smaller galaxies. The M_BH-R_b relation exhibits 30-47% less scatter than the M_BH-σ relation for the same sample. The authors interpret this high-mass upturn as evidence that ultramassive black holes grew through successive major, dry mergers—a scenario that also explains the observed flattening of the σ-L_V relation at the brightest galaxy magnitudes.
What's missing
The study does not discuss potential observational biases in black hole mass measurements or selection effects that might affect the sample composition. Additionally, the paper does not address how these findings compare to or constrain cosmological simulations of galaxy and black hole co-evolution.
What different sources said
- arXiv astro-phCenter
The $M_{\rm BH}$$-$$R_{\rm b}$ relation and the high-mass end of the $M_{\rm BH}$$-$$\sigma$ relation
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