Pathways to massive black holes and compact star clusters in pre-galactic dark matter haloes with virial temperatures ≳10 000 K

Abstract

Large dynamic range numerical simulations of atomic cooling driven collapse of gas in pregalactic dark matter haloes with T vir ∼ 10 000 K show that the gas loses 90 per cent and more of its angular momentum before rotational support sets in. In a fraction of these haloes where the metallicity is low and ultraviolet (UV) radiation suppresses H 2 cooling, conditions are thus very favourable for the rapid build-up of massive black holes. Depending on the progression of metal enrichment, the continued suppression of H 2 cooling by external and internal UV radiation and the ability to trap the entropy produced by the release of gravitational energy, the gas at the centre of the halo is expected to form a supermassive star, a stellar-mass black hole accreting at super-Eddington accretion rates or a compact star-cluster undergoing collisional run-away of massive stars at its centre. In all three cases, a massive black hole of initially modest mass finds itself at the centre of a rapid inflow of gas with inflow rates of 1 M yr −1 . The massive black hole will thus grow quickly to a mass of 10 5 -10 6 M until further inflow is halted either by consumption of gas by star formation or by the increasing energy and momentum feedback from the growing massive black hole. Conditions for the formation of massive seed black holes in this way are most favourable in haloes with T vir ∼ 15 000 K and V vir ∼ 20 km s −1 with less massive haloes not allowing collapse of gas by atomic cooling and more massive haloes being more prone to fragmentation. This should imprint a characteristic mass on the mass spectrum of an early population of massive black hole seeds in pre-galactic haloes which will later grow into the observed population of supermassive black holes in galactic bulges.

Revised rate coefficients for H2 and H− destruction by realistic stellar spectra

“…Eisenstein & Loeb 1995;Oh & Haiman 2002;Bromm & Loeb 2003;Koushiappas et al 2004;Lodato & Natarajan 2006;Regan & Haehnelt 2009), where a critical level of LW specific intensity (Jcrit) is essential in suppressing H2 cooling. Previous studies have done an excellent job at computing the critical level of LW intensity by assuming either a T4 or T5 type spectrum for the irradiating sources (Omukai 2001;Shang et al 2010;Wolcott-Green et al 2011;Latif et al 2014).…”

Formation of supermassive black holes

“…The efficiency of the mass assembly process ceases at large halo masses, where the mass-accretion rate from the halo is above the critical threshold for fragmentation and the disc undergoes global star formation instead ( Figure 2, lower panel). Wise et al (2008) and Regan and Haehnelt (2009) have performed some idealized numerical simulations of the evolution of gaseous discs in haloes with suitable characteristics. In their simulations, the gas can then lose up to 90% of its angular momentum due to supersonic turbulent motions, settling eventually into rotationally supported fat discs, in a very compact configuration.…”

Warm dark matter constraints from high-z direct collapse black holes using the JWST

“…First postulated as massive (10 5−6 M ) black hole seeds, to explain the presence of super-massive black holes (SMBH) at early cosmic epochs (e.g. Loeb & Rasio 1994;Bromm & Loeb 2003), DCBH formation scenarios have been continually refined and developed over the past years (e.g Begelman et al 2006;Regan & Haehnelt 2009;Shang et al 2010;Johnson et al 2012;Latif et al 2013;Agarwal et al 2014;Dijkstra et al 2014;Ferrara et al 2014;Habouzit et al 2016). This field has been lent impetus by the possible, albeit highly debated (Sobral et al 2015;Bowler et al 2017), detection of a DCBH (Agarwal et al 2016;Hartwig et al 2016;Smith et al 2016;Pacucci et al 2017) in the Lyman Alpha Emitting "CR7" galaxy at z ∼ 7.…”