Super-Eddington growth of the first black holes
Date Issued
2016
Author(s)
Abstract
The assembly of the first super massive black holes (SMBHs) at z ≳ 6 is still a subject of intense debate. If black holes (BHs) grow at their Eddington rate, they must start from ≳104 M☉ seeds formed by the direct collapse of gas. Here, we explore the alternative scenario where ∼100 M☉ BH remnants of the first stars grow at super-Eddington rate via radiatively inefficient slim accretion discs. We use an improved version of the cosmological, data-constrained semi-analytic model GAMETE/QSODUST, where we follow the evolution of nuclear BHs and gas cooling, disc and bulge formation of their host galaxies. Adopting SDSS J1148+5251 (J1148) at z = 6.4 as a prototype of luminous z ≳ 6 quasars, we find that ∼80 per cent of its SMBH mass is grown by super-Eddington accretion, which can be sustained down to z ∼ 10 in dense, gas-rich environments. The average BH mass at z ∼ 20 is MBH ≳ 104 M☉, comparable to that of direct collapse BHs. At z = 6.4 the AGN-driven mass outflow rate is consistent with the observations and the BH-to-bulge mass ratio is compatible with the local scaling relation. However, the stellar mass in the central 2.5 kpc is closer to the value inferred from CO observations. Finally, ∼20 per cent of J1148 progenitors at z = 7.1 have BH luminosities and masses comparable to ULAS J1120+0641, suggesting that this quasar may be one of the progenitors of J1148.
Volume
458
Issue
3
Start page
3047
Issn Identifier
0035-8711
Ads BibCode
2016MNRAS.458.3047P
Rights
open.access
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