Abstract
Abstract Active galactic nuclei (AGNs) probably control the growth of their host galaxies via feedback in the form of wide-angle wind-driven outflows. These establish the observed correlations between supermassive black hole (SMBH) masses and host galaxy properties, e.g. the spheroid velocity dispersion σ. In this paper we consider the growth of the SMBH once it starts driving a large-scale outflow through the galaxy. To clear the gas and ultimately terminate further growth of both the SMBH and the host galaxy, the black hole must continue to grow its mass significantly, by up to a factor of a few, after reaching this point. The mass increment ΔMBH depends sensitively on both galaxy size and SMBH spin. The galaxy size dependence leads to ΔMBH ∝ σ5 and a steepening of the M–σ relation beyond the analytically calculated M ∝ σ4, in agreement with observation. Slowly spinning black holes are much less efficient in producing feedback, so at any given σ the slowest spinning black holes should be the most massive. Current observational constraints are consistent with this picture, but insufficient to test it properly; however, this should change with upcoming surveys.
Highlights
It is generally accepted that most galaxies harbour supermassive black holes (SMBHs) in their centres
There are few robust estimates of SMBH spins available in the literature, but the available data show a general trend of more massive black holes spinning more slowly (Brenneman 2013; Reynolds 2013; Vasudevan et al 2016; Reynolds 2019)
Selection effects mean that a lot of low-spin SMBHs are undetected (Vasudevan et al 2016), it is impossible to predict what mass range they might fall in
Summary
It is generally accepted that most galaxies harbour supermassive black holes (SMBHs) in their centres. The AGN wind-driven outflow model can explain the salient properties of these outflows, as well as their scaling with AGN luminosity (Zubovas & King 2012b) This model explains the observed correlation between SMBH masses and the velocity dispersion in the host galaxy (the M–σ relation, cf Kormendy & Ho 2013; McConnell & Ma 2013). In this model, the AGNs can only drive large-scale outflows once its luminosity reaches a critical threshold.
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