Supermassive black hole formation during the assembly of pre-galactic discs

Abstract

In this paper, we discuss the evolution of gravitationally unstable pre‐galactic discs that result from the collapse of haloes at high redshift z≈ 10 or so, which have not yet been enriched by metals. In cases where molecular hydrogen formation is suppressed, the discs are maintained at a temperature of a few thousand Kelvin. However, when molecular hydrogen is present, cooling can proceed down to a few hundred Kelvin. Analogous to the case of the larger‐scale protogalactic discs, we assume that the evolution of these discs is mainly driven by angular momentum redistribution induced by the development of gravitational instabilities in the disc. We also properly take into account the possibility of disc fragmentation. We thus show that this simple model naturally predicts the formation of supermassive black holes in the nuclei of such discs and provides a robust determination of their mass distribution as a function of halo properties. We estimate that roughly 5 per cent of discs resulting from the collapse of haloes with M≈ 107 M⊙ should host a massive black hole with a mass MBH≈ 105 M⊙. We confirm our arguments with time‐dependent calculations of the evolution of the surface density and of the accretion rate in these primordial discs. The luminosity of the outer, colder disc is expected to be very low (in the range of a few thousand L⊙), while the formation of the black hole is expected to produce a burst with a luminosity of a few times 109 L⊙. This mechanism offers an efficient way to form seed black holes at high redshift. The predicted masses for our black hole seeds enable the comfortable assembly of 109‐M⊙ black holes powering the luminous quasars detected by the Sloan Digital Sky Survey at z= 6 for a concordance cosmology.

Simulating the growth of intermediate-mass black holes

“…The UV specific intensity in the LW band, Jν = J * 21 × 10 −21 erg s −1 cm −2 Hz −1 sr −1 , required for quenching is somewhat uncertain, but lies in the range J * 21 = 0.1 − 1 (see, e.g., Machacek et al 2001 andFialkov et al 2013). When instead primordial, atomic-cooling halos (Tvir > 10 4 K) are exposed to a LW flux of even higher intensity, Jν > J • ν (Loeb & Rasio 1994;Eisenstein & Loeb 1995;Begelman et al 2006;Lodato & Natarajan 2006;Regan & Haehnelt 2009;Shang et al 2010;Johnson et al 2012;Agarwal et al 2012;Latif et al 2013a) the destruction of H2 molecules allows a rapid, isothermal collapse, initially driven by H I Lyα line cooling, later replaced by two-photon emission. The precise value of J • ν depends on several factors, but there is a general consensus that it should fall in the range 30 < J • 21 < 1000, depending on the spectrum of the sources (Sugimura et al 2014).…”

Effects of post-Newtonian spin alignment on the distribution of black-hole recoils

“…More recent theoretical work has called into question whether the high-redshift seeds of SBHs were truly this massive. While some maintain that massive central concentrations of gas at the centers of pre-galactic disks can directly collapse into ∼ 10 5 M ⊙ SBH seeds [31], others argue that metal-free gas will fragment into Population III stars with characteristic masses 100M ⊙ [32]. Volonteri, Haardt, and Madau [33], also using the Press-Schechter formalism to estimate halo mass functions and merger rates, showed that 150 M ⊙ seeds occupying 3.5 − 4σ overdensities at redshift z = 20 could grow into SBHs that would reproduce both the quasar luminosity function at 1 ≤ z ≤ 5 and the observed local M BH −σ relation [3] between SBH mass and galaxy velocity dispersion.…”

Hyper-Eddington mass accretion on to a black hole with super-Eddington luminosity

“…One is remnant BHs of massive Population III (Pop III) stars with ∼ 100 M (Madau & Rees 2001;Haiman & Loeb 2001;Schneider et al 2002;Islam, Taylor & Silk 2003;Volonteri, Haardt & Madau 2003;Tanaka & Haiman 2009). Second, the socalled direct collapse model (Loeb & Rasio 1994;Oh & Haiman 2002;Bromm & Loeb 2003;Begelman, Volonteri & Rees 2006;Lodato & Natarajan 2006;Shang, Bryan & 2014). When the BH is fed by sufficiently strong gas flows, and the emergent luminosity increases, radiative feedback is likely to affect gas dynamics.…”