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

Abstract

We perform one-dimensional radiation hydrodynamical simulations to solve accretion flows onto massive black holes (BHs) with a very high rate. Assuming that photon trapping limits the luminosity emerging from the central region to L L Edd , Inayoshi, Haiman & Ostriker (2016) have shown that an accretion flow settles to a "hyper-Eddington" solution, with a steady and isothermal (T 8000 K) Bondi profile reaching 5000 times the Eddington accretion rateṀ Edd ≡ L Edd /c 2 . Here we address the possibility that gas accreting with finite angular momentum forms a bright nuclear accretion disc, with a luminosity exceeding the Eddington limit (1 L/L Edd 100). Combining our simulations with an analytic model, we find that a transition to steady hyper-Eddington accretion still occurs, as long as the luminosity remains below L/L Edd 35 (M BH /10 4 M ) 3/2 (n ∞ /10 5 cm −3 )(T ∞ /10 4 K) −3/2 (r /10 14 cm) −1/2 , where n ∞ and T ∞ are the density and temperature of the ambient gas, and r is the radius of the photosphere, at which radiation emerges. If the luminosity exceeds this value, accretion becomes episodic. Our results can be accurately recovered in a toy model of an optically thick spherical shell, driven by radiation force into a collapsing medium. When the central source is dimmer than the above critical value, the expansion of the shell is halted and reversed by ram pressure of the collapsing medium, and by shell's weight. Our results imply that rapid, unimpeded hyper-Eddington accretion is possible even if the luminosity of the central source far exceeds the Eddington limit, and can be either steady or strongly episodic.

Formation of intermediate-mass black holes through runaway collisions in the first star clusters

“…If near-Eddington accretion is sustained with accretion efficiency of 10%, a 1000 M seed BH grows to become as massive as ∼ 10 9 M in ∼ 0.6 Gyr (e.g. Sakurai, Inayoshi & Haiman 2016). We conclude that IMBH formation in dense star clusters offers a viable mechanism for seeding SMBHs.…”

Active Galactic Nuclei: Boon or Bane for Biota?

“…In both cases, we will suppose that the planets under consideration have sufficiently thick atmospheres to avoid being completed eroded due to AGNs. 3 also possible (Sakurai et al 2016;Collinson et al 2017;Begelman & Volonteri 2017;Woods et al 2018).…”

Searching for super-Eddington quasars using a photon trapping accretion disc model

“…In the latter case, the photon trapping effects are mitigated, and the disc luminosity is expected to continue increasing with m, as opposed to remaining in the 1 − 10L Edd range (Ohsuga et al 2002). The realistic scenario may be even more complicated than currently considered, though many studies agree that some form of photon trapping yielding the effects described above is required in order to successfully account of super-Eddington accretion onto SMBHs (Ohsuga et al 2002(Ohsuga et al , 2003Mineshige & Ohsuga 2008;McKinney et al 2014;Sadowski et al 2014;Inayoshi et al 2016;Sakurai et al 2016;Sadowski & Narayan 2016). In what follows, we thus proceed by investigating a rather simplistic model for photon trapping, and show that this can already result in intriguing insights regarding the identification of super-Eddington AGN.…”

“…(Ohsuga et al 2002(Ohsuga et al , 2003Mineshige & Ohsuga 2008;Sadowski et al 2014;Sadowski & Narayan 2016). As such, it is suggested that too many photons are allowed to escape in the regular slim disc model, leading to an overestimation of the disc luminosity (Ohsuga et al 2002(Ohsuga et al , 2003Mineshige & Ohsuga 2008;Inayoshi et al 2016;Sakurai et al 2016). Moreover, photon trapping effects are expected to significantly change the shape of the emergent SED, as (UV) photons from the inner parts of the accretion flow are advected onto the BH.…”