Two channels of supermassive black hole growth as seen on the galaxies mass-size plane

Journal article

We investigate the variation of black hole masses (MBH) as a function of their host galaxy stellar mass (M∗) and half-light radius (Re). We confirm that the scatter in MBH within this plane is essentially the same as that in the MBH–σ relation, as expected from the negligible scatter reported in the virial mass estimator σ2v = G × M∗/(5 × Re). All variation in MBHhappens along lines of constant σv on the (M∗, Re) plane, or M∗ ∝ Re for M∗ ≲ 2 × 1011 M⊙. This trend is qualitatively the same as those previously reported for galaxy properties related to stellar populations, like age, metallicity, alpha enhancement, mass-to-light ratio and gas content. We find evidence for a change in the MBH variation above the critical mass of Mcrit ≈ 2 × 10^11 M⊙. This behaviour can be explained assuming that MBH in galaxies less massive thanMcrit can be predicted by theMBH–σ relation, whileMBH in more massive galaxies follows a modified relation, which is also dependent onM∗ onceM∗ >Mcrit. This is consistent with the scenario where the majority of galaxies grow through star formation, while the most massive galaxies undergo a sequence of dissipation-less mergers. In both channels, black holes and galaxies grow synchronously, giving rise to the black hole–host galaxy scaling relations, but there is no underlying single relation that is universal across the full range of galaxy masses.

Authors: Krajnović, D; Cappellari, M; McDermid, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 473
• Issue: 4
• Pages: 5237-5247
• Publication date: 2017-10-01
• Acceptance date: 2017-10-13
• DOI: 10.1093/mnras/stx2704
• EISSN: 1365-2966
• ISSN: 0035-8711
• Keywords: galaxies: fundamental parameters; quasars: supermassive black holes; galaxies: evolution