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Slow and massive: low-spin SMBHs can grow more
journal contributionposted on 2019-11-27, 16:50 authored by Kastytis Zubovas, Andrew King
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.
This work was funded by the Research Council Lithuania grant no. MIP-17-78. Theoretical astrophysics in Leicester is supported by an Science and Technologies Facilities Council Consolidated Grant.
CitationMonthly Notices of the Royal Astronomical Society, Volume 489, Issue 1, October 2019, Pages 1373–1378, https://doi.org/10.1093/mnras/stz2235
Author affiliationDepartment of Physics & Astronomy
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