Date:
Tue, 20/06/201712:30-13:30
Limits on the growth rate of supermassive black holes at early cosmic epochs
It is shown, based on recent numerical simulations and observations of quasar outflows, that the rate at which gas can be supplied to a supermassive black hole (SMBH) at the center of a young galaxy, is limited to $\sim 20 (\sigma/400~ {\rm km ~s^{-1}})^4~M_\odot/yr$, where $\sigma$ is the velocity dispersion of the host bulge, by action of winds expelled from the innermost regions of the accretion flow. This rate is independent of the BH mass and only weakly dependent on the accretion mode (super or sub Eddington), but is sensitive to the properties of the host bulge.
About 1 Gyr after the onset of the accretion phase, gas inflow is quenched and the accretion rate is strongly suppressed. This result is in remarkable agreement with recent observations, as it (i) reveals the origin of the maximal observed accretion rates, (ii) accounts for the inferred growth rate of SMBHs at high redshift (independent of their initial seeds masses), (iii) elucidates the decline in the accretion rate at lower redshifts, and (iv) explains the relation between $\sigma$ and the mass $M_{BH}$ of the central SMBH, measured in the local Universe.
It is shown, based on recent numerical simulations and observations of quasar outflows, that the rate at which gas can be supplied to a supermassive black hole (SMBH) at the center of a young galaxy, is limited to $\sim 20 (\sigma/400~ {\rm km ~s^{-1}})^4~M_\odot/yr$, where $\sigma$ is the velocity dispersion of the host bulge, by action of winds expelled from the innermost regions of the accretion flow. This rate is independent of the BH mass and only weakly dependent on the accretion mode (super or sub Eddington), but is sensitive to the properties of the host bulge.
About 1 Gyr after the onset of the accretion phase, gas inflow is quenched and the accretion rate is strongly suppressed. This result is in remarkable agreement with recent observations, as it (i) reveals the origin of the maximal observed accretion rates, (ii) accounts for the inferred growth rate of SMBHs at high redshift (independent of their initial seeds masses), (iii) elucidates the decline in the accretion rate at lower redshifts, and (iv) explains the relation between $\sigma$ and the mass $M_{BH}$ of the central SMBH, measured in the local Universe.