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Free keywords:
black hole physics
dark ages
reionization
first stars
early
universe
galaxies: active
galaxies: evolution
quasars: supermassive
black holes
Astrophysics - Astrophysics of Galaxies
Astrophysics -
Cosmology and Nongalactic Astrophysics
Astrophysics - High Energy
Astrophysical Phenomena
Abstract:
The {M}\bullet {--}σ relation establishes a connection between central black holes (BHs) and their host spheroids. Supported by observations at {M}\bullet ≳ {10}5 {M}☉ , there is limited data on its validity at lower masses. Employing a semi-analytical model to simulate the combined evolution of BHs and their host galaxies, we predict the observational consequences of assuming a bimodality in the accretion efficiency of BHs, with low-mass BHs ({M}\bullet ≲ {10}5 {M}☉ ) accreting inefficiently. We predict a departure from the {M}\bullet {--}σ relation at a transitional BH mass ̃ {10}5 {M}☉ , with lower-mass BHs unable to reach the mass dictated by the relation and becoming disconnected from the evolution of the host galaxy. This prediction is an alternative to previous works suggesting a flattening of the relation at ̃ {10}5{--}{10}6 {M}☉ . Furthermore, we predict a deficit of BHs shining at bolometric luminosities ̃ {10}42 {erg} {{{s}}}-1. Joined with a detection bias, this could partly explain the scarce number of intermediate-mass BHs detected. Conversely, we predict an increase in source density at lower bolometric luminosities, < {10}42 {erg} {{{s}}}-1. Because our predictions assume a bimodal population of high-redshift BH seeds, future observations of fainter BHs will be fundamental for constraining the nature of these seeds.
